Scale and the isotopic record of C4 plants in pedogenic carbonate: from the biome to the rhizospere.

Energy Technology Data Exchange (ETDEWEB)

Monger, Dr. H Curtis [New Mexico State University, Las Cruces; Cole, David R [ORNL; Buck, Dr. Brenda [University of Nevada, Las Vegas; Gallegos, Robert [Sant fe Water Division

2009-01-01

The 13C/12C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaning of d13C values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that reveal four scales important for paleoecologic interpretations. (1) At the broadest scale, the biome scale (hundreds to millions of km2), an isotopic record interpreted as C3 vegetation replacing C4 grasslands may indicate invading C3 woody shrubs instead of expanding C3 forests (a common interpretation). (2) At the landscape scale (several tens of m2 to hundreds of km2), the accuracy of scaling up paleoclimatic interpretations to a regional level is affected by the landform containing the isotopic record. (3) At the soil-profile scale (cm2 to m2), soil profiles with multiple generations of carbonate mixed together have a lower-resolution paleoecologic record than soil profiles repeatedly buried. (4) At the rhizosphere scale (lm2 to cm2), carbonate formed on roots lack the 14 17 enrichment observed at broader scales, revealing different fractionation processes at different scales. A multi-scale approach in dealing with d13C in pedogenic carbonate will increase the accuracy of paleoecologic interpretations and understanding of soil geomorphic climatic interactions that affect boundaries between C4 and C3 vegetation.

Scale and the isotopic record of C4 plants in pedogenic carbonate: from the biome to the rhizosphere

Energy Technology Data Exchange (ETDEWEB)

Monger, Dr. H Curtis [New Mexico State University, Las Cruces; Cole, David [Ohio State University; Buck, Dr. Brenda [University of Nevada, Las Vegas; Gallegos, Robert [Sant fe Water Division

2009-01-01

The 13C/12C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaning of d13C values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that reveal four scales important for paleoecologic interpretations. (1) At the broadest scale, the biome scale (hundreds to millions of km2), an isotopic record interpreted as C3 vegetation replacing C4 grasslands may indicate invading C3 woody shrubs instead of expanding C3 forests (a common interpretation). (2) At the landscape scale (several tens of m2 to hundreds of km2), the accuracy of scaling up paleoclimatic interpretations to a regional level is affected by the landform containing the isotopic record. (3) At the soil-profile scale (cm2 to m2), soil profiles with multiple generations of carbonate mixed together have a lower-resolution paleoecologic record than soil profiles repeatedly buried. (4) At the rhizosphere scale (lm2 to cm2), carbonate formed on roots lack the 14 17 enrichment observed at broader scales, revealing different fractionation processes at different scales. A multi-scale approach in dealing with d13C in pedogenic carbonate will increase the accuracy of paleoecologic interpretations and understanding of soil geomorphic climatic interactions that affect boundaries between C4 and C3 vegetation.

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

DEFF Research Database (Denmark)

Hesselbo, Stephen P.; Korte, Christoph

2010-01-01

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

Stable and strontium isotopic records of molluscan shells, lower jurassic, Cuenca Neuquina, southwestern Mendoza, Argentina

International Nuclear Information System (INIS)

Cagnoni, M.C.; Valencio, S.A.; Ramos, A.M; Riccardi, A.C; Panarello, H.O

2001-01-01

The strontium, carbon and oxygen isotopic signal of the past oceans is accurately recorded by authigenic marine minerals such as carbonates, sulfates and phosphates. The variation of these isotope ratios through the geological time is used as a tool in correlating and dating marine sedimentary rocks. Many works have been done concerning to the changes in carbon, oxygen and strontium isotope ratios of different marine successions in the world. These allow the construction of curves of secular variations of the isotope signals with geological time (Jones et al., 1994a, 1994b; Veizer et al., 1999; Jacobsen and Kaufman, 1999). This work presents strontium, carbon and oxygen isotope ratios of Early Jurassic biogenic marine carbonates of Cuenca Neuquina in southwestern Mendoza (au)

Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

International Nuclear Information System (INIS)

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

1994-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

CO2-dependent carbon isotope fractionation in the dinoflagellate Alexandrium tamarense

Science.gov (United States)

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

2017-09-01

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

Carbon 13 and oxygen 18 isotope record of the early eocene nammal formation, salt range, pakistan

International Nuclear Information System (INIS)

Ghazi, S.; Sajid, Z.

2014-01-01

The Nammal Formation is the lowermost unit of the Early Eocene succession in the Salt Range, Pakistan. It is well exposed throughout the Salt Range. The Nammal Formation having 30 to 35 meters thickness is predominantly composed of nodular limestone interbedded with marl and shale. The present study was focussed on stable carbon 13 and oxygen 18 isotopic analysis based on data from two stratigraphically important sections. The samples from the Nilawahan section provided with the delta 13C values varied between 1.34 to -1.56 (VPDB) and values of delta 18O fluctuated between -4.47 to -6.59 (VPDB). Likewise the sample analysis of BadshahPur section exhibited that the delta 13C values changes from 1.09 to -1.65 (VPDB) and delta 18O values range from -4.17 to -6.85 (VPDB). The isotopic records of carbon 13 and oxygen 18 indicated the shallow marine deposition of the Nammal Formation under tropical conditions. It highlighted the palaeo climatic and diagenetic conditions of the Nammal Formation at the time of deposition in the Salt Range region. (author)

Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

Science.gov (United States)

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

2012-12-01

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

Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

Science.gov (United States)

Auer, Gerald; Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

2015-04-01

During the Miocene prominent oxygen isotope events (Mi-events) reflect major changes in glaciation, while carbonate isotope maxima (CM-events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high-resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long-term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi-events can now be recognized in the δ18O record and coincide with plankton-rich, siliceous, or phosphatic horizons in the lithology of the section.

Carbon isotopes in mollusk shell carbonates

Science.gov (United States)

McConnaughey, Ted A.; Gillikin, David Paul

2008-10-01

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

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

Science.gov (United States)

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

2015-04-30

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

Triple oxygen isotopes in biogenic and sedimentary carbonates

Science.gov (United States)

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

2014-09-01

The 17O anomaly (Δ17O) of natural waters has been shown to be sensitive to evaporation in a way analogous to deuterium excess, with evaporated bodies of water (e.g., leaf waters, lake waters, animal body waters) tending to have lower Δ17O than primary meteoric waters. In animal body water, Δ17O relates to the intake of evaporated waters, evaporative effluxes of water, and the Δ17O value of atmospheric O2, which itself carries signatures of global carbon cycling and photochemical reactions in the stratosphere. Carbonates have the potential to record the triple oxygen isotope compositions of parent waters, allowing reconstruction of past water compositions, but such investigations have awaited development of methods for high-precision measurement of Δ17O of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield Δ17O data with the high precision (∼0.010‰, 1σ) needed to resolve subtle environmental signals. We report the first high-precision Δ17O dataset for terrestrial carbonates, focusing on vertebrate biogenic carbonates and soil carbonates, but also including marine invertebrates and high-temperature carbonates. We determine apparent three-isotope fractionation factors between the O2 analyte derived from carbonate and the parent waters of the carbonate. These in combination with appropriate temperature estimates (from clumped isotope thermometry, or known or estimated body temperatures) are used to calculate the δ18O and Δ17O of parent waters. The clearest pattern to emerge is the strong 17O-depletion in avian, dinosaurian, and mammalian body water (from analyses of eggshell and tooth enamel) relative to meteoric waters, following expected influences of evaporated water (e.g., leaf water) and atmospheric O2 on vertebrate body water. Parent waters of the soil carbonates studied here have Δ17O values that are similar to or slightly lower than global precipitation. Our results suggest

A 40-year record of Northern Hemisphere atmospheric carbon monoxide concentration and isotope ratios from the firn at Greenland Summit.

Science.gov (United States)

Place, P., Jr.; Petrenko, V. V.; Vimont, I.; Buizert, C.; Lang, P. M.; Edwards, J.; Harth, C. M.; Hmiel, B.; Mak, J. E.; Novelli, P. C.; Brook, E.; Weiss, R. F.; Vaughn, B. H.; White, J. W. C.

2014-12-01

Carbon Monoxide (CO) is an important atmospheric trace gas that affects the oxidative capacity of the atmosphere and contributes indirectly to climate forcing by being a major sink of tropospheric OH. A good understanding of the past atmospheric CO budget is therefore important for climate models attempting to characterize recent changes in the atmosphere. Previous work at NEEM, Greenland provided the first reconstructions of Arctic atmospheric history of CO concentration and stable isotope ratios (δC18O and δ13CO) from firn air, dating to the 1950s. In this new study, firn air was sampled from eighteen depth levels through the firn column at Summit, Greenland (in May 2013), yielding a second, independent record of Arctic CO concentration and isotopic ratios. Carbon monoxide stable isotope ratios were analyzed on replicate samples and using a newly developed system with improved precision allowing for a more robust reconstruction. The new CO concentration and stable isotope results overall confirm the earlier findings from NEEM, with a CO concentration peak around the 1970s and higher δC18O and δ13CO values associated with peak CO. Modeling and interpretation of the data are in progress.

Speleothem records of acid sulphate deposition and organic carbon mobilisation

Science.gov (United States)

Wynn, Peter; Fairchild, Ian; Bourdin, Clement; Baldini, James; Muller, Wolfgang; Hartland, Adam; Bartlett, Rebecca

2017-04-01

Dramatic increases in measured surface water DOC in recent decades have been variously attributed to either temperature rise, or destabilisation of long-term soil carbon pools following sulphur peak emissions status. However, whilst both drivers of DOC dynamics are plausible, they remain difficult to test due to the restricted nature of the available records of riverine DOC flux (1978 to present), and the limited availability of SO2 emissions inventory data at the regional scale. Speleothems offer long term records of both sulphur and carbon. New techniques to extract sulphur concentrations and isotopes from speleothem calcite have enabled archives of pollution history and environmental acidification to be reconstructed. Due to the large dynamic range in sulphur isotopic values from end member sources (marine aerosol +21 ‰ to continental biogenic emissions -30 ‰) and limited environmental fractionation under oxidising conditions, sulphur isotopes form an ideal tracer of industrial pollution and environmental acidification in the palaeo-record. We couple this acidification history to the carbon record, using organic matter fluorescence and trace metals. Trace metal ratios and abundance can be used to infer the type and size of organic ligand and are therefore sensitive to changes in temperature as a driver of organic carbon processing and biodegradation. This allows fluorescent properties and ratios of trace metals in speleothem carbonate to be used to represent both the flux of organic carbon into the cave as well as the degradation pathway. Here we present some of the first results of this work, exploring sulphur acidification as a mechanistic control on carbon solubility and export throughout the twentieth century.

Carbon and hydrogen isotopic effects of stomatal density in Arabidopsis thaliana

Science.gov (United States)

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

2016-04-01

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

A new record of the Paleocene Carbon Isotope Maximum from the Mississippi Embayment

Science.gov (United States)

Platt, B. F.; Gerweck, E. D.

2017-12-01

The Paleocene-Eocene interval is well known as a time of climatic transitions, especially hyperthermals associated with disturbances in the carbon cycle that are used as proxies for impacts of projected anthropogenic global climate change. A recent roadcut in Benton County, Mississippi exposes a disconformity between the Paleocene Naheola Formation and the Eocene Meridian Sand. The disconformity is developed on a thick, kaolinitic paleosol, which we interpret as a mature Oxisol that supported tropical rainforest vegetation (as evidenced by associated well preserved leaf fossils). The nature of the paleosol at the disconformity led us to hypothesize that the strata might contain evidence of the Paleocene Eocene Thermal Maximum (PETM). We sampled two Mississippi Mineral Resources Institute (MMRI) cores from the equivalent stratigraphic interval from Benton and Tippah Counties, Mississippi, for bulk organic carbon stable isotopes at 25-cm intervals. Results showed no evidence of the negative excursion characteristic of the PETM. Instead, we found a gradual upsection enrichment that we interpret as the positive trend characteristic of the lower Paleocene Carbon Isotope Maximum (PCIM). This is reasonable based on published biostratigraphy and absolute ages from elsewhere in the Naheola Formation. Further analyses will be performed to determine whether the PCIM trend continues throughout the remainder of the core. The identification of the PCIM in Mississippi Embayment (ME) sediments is important because stable carbon isotope data may be useful for improving chronostratigraphy in the ME. Also, the PCIM is associated with a gradual warming trend as indicated by previously published stable oxygen isotopes from benthic foraminifera. Studying successive ME paleosols throughout the PCIM may yield information about the impacts of gradual atmospheric warming on soils and associated terrestrial systems.

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

Science.gov (United States)

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

2018-02-01

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

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

Science.gov (United States)

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

2013-04-01

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

Modeling the carbon isotope composition of bivalve shells (Invited)

Science.gov (United States)

Romanek, C.

2010-12-01

relations dictate that shell carbonate should be preferentially enriched in C-13 by 3 to 5 per mill (from 30° to 0°C) compared to EPF at a pH of 7.5. Anomalous positive excursions are rarely, if ever, observed in shell carbonate and they have yet to be associated with growth cessation markers in bivalves. The most likely explanation for the lack of anomalous positive values is that the percentage of metabolic carbon increases in EPF when bivalves experience stressful condition. This influx of metabolic carbon is balanced to a measureable extent by the enhanced fractionation of carbon isotopes during shell deposition from EPF at relatively low pH. These two processes may be combined in a quantitative model to extract a historical record of metabolic activity from the carbon isotope profiles of bivalve shells.

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

Science.gov (United States)

Price, Gregory; Grimes, Stephen

2015-04-01

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

Measurements of flux and isotopic composition of soil carbon dioxide

International Nuclear Information System (INIS)

Gorczyca, Z.; Rozanski, K.; Kuc, T.

2002-01-01

The flux and isotope composition of soil CO 2 has been regularly measured at three sites located in the southern Poland, during the time period: January 1998 - October 2000. They represent typical ecosystems appearing in central Europe: (i) mixed forest; (ii) cultivated agricultural field; (iii) grassland. To monitor the flux and isotopic composition of soil CO 2 , a method based on the inverted cup principle was adopted. The flux of soil CO 2 reveals distinct seasonal fluctuations, with maximum values up to ca. 25 mmol/m 2 /h during sommer months and around ten times lower values during winter time. Also significant differences among the monitored sites were detected, the flux density of this gas being highest for the mixed forest site and ca. two times lower for the cultivated grassland. Carbon-13 content of the soil CO 2 reveals little seasonal variability, with δ 13 C values essentially reflecting the isotopic composition of the soil organic matter and the vegetation type. The carbon-14 content of soil CO 2 flux also reveals slight seasonality, with lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values were recorded at depth. (author)

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

DEFF Research Database (Denmark)

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

2013-01-01

documented from oceanic settings (i.e., lack of positive excursion of carbon-isotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbon-isotope records include reworking from older deposits, degradation and diagenesis, as well....../or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion...... is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-of-slope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure....

Carbon isotopes in biological carbonates: Respiration and photosynthesis

Science.gov (United States)

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

1997-02-01

Respired carbon dioxide is an important constituent in the carbonates of most air breathing animals but is much less important in the carbonates of most aquatic animals. This difference is illustrated using carbon isotope data from freshwater and terrestrial snails, ahermatypic corals, and chemoautotrophic and methanotrophic pelecypods. Literature data from fish otoliths and bird and mammal shell and bone carbonates are also considered. Environmental CO 2/O 2 ratios appear to be the major controlling variable. Atmospheric CO 2/O 2 ratios are about thirty times lower than in most natural waters, hence air breathing animals absorb less environmental CO 2 in the course of obtaining 0 2. Tissue CO 2 therefore, does not isotopically equilibrate with environmental CO 2 as thoroughly in air breathers as in aquatic animals, and this is reflected in skeletal carbonates. Animals having efficient oxygen transport systems, such as vertebrates, also accumulate more respired CO 2 in their tissues. Photosynthetic corals calcify mainly during the daytime when photosynthetic CO 2 uptake is several times faster than respiratory CO 2 release. Photosynthesis, therefore, affects skeletal δ13C more strongly than does respiration. Corals also illustrate how "metabolic" effects on skeletal isotopic composition can be estimated, despite the presence of much larger "kinetic" isotope effects.

Effects of ocean acidification on the marine calcium isotope record at the Paleocene-Eocene Thermal Maximum

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Griffith, Elizabeth M.; Fantle, Matthew S.; Eisenhauer, Anton; Paytan, Adina; Bullen, Thomas D.

2015-06-01

Carbonates are used extensively to reconstruct paleoclimate and paleoceanographic conditions over geologic time scales. However, these archives are susceptible to diagenetic alteration via dissolution, recrystallization and secondary precipitation, particularly during ocean acidification events when intense dissolution can occur. Despite the possible effects of diagenesis on proxy fidelity, the impacts of diagenesis on the calcium isotopic composition (δ44Ca) of carbonates are unclear. To shed light on this issue, bulk carbonate δ44Ca was measured at high resolution in two Pacific deep sea sediment cores (ODP Sites 1212 and 1221) with considerably different dissolution histories over the Paleocene-Eocene Thermal Maximum (PETM, ∼ 55 Ma). The δ44Ca of marine barite was also measured at the deeper Site 1221, which experienced severe carbonate dissolution during the PETM. Large variations (∼ 0.8 ‰) in bulk carbonate δ44Ca occur in the deeper of the two sites at depths corresponding to the peak carbon isotope excursion, which correlate with a large drop in carbonate weight percent. Such an effect is not observed in either the 1221 barite record or the bulk carbonate record at the shallower Site 1212, which is also less affected by dissolution. We contend that ocean chemical changes associated with abrupt and massive carbon release into the ocean-atmosphere system and subsequent ocean acidification at the PETM affected the bulk carbonate δ44Ca record via diagenesis in the sedimentary column. Such effects are considerable, and need to be taken into account when interpreting Ca isotope data and, potentially, other geochemical proxies over extreme climatic events that drive sediment dissolution.

Stable isotopes of pedogenic carbonates from the Somma-Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications

Science.gov (United States)

Zanchetta, G.; di Vito, M.; Fallick, A. E.; Sulpizio, R.

2000-12-01

Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma-Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in 18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1 in 18O of pedogenic carbonate recorded after this eruption. The 13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.

A carbon isotope challenge to the snowball Earth.

Science.gov (United States)

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

2011-10-05

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

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

Czech Academy of Sciences Publication Activity Database

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

2015-01-01

Roč. 1, č. 2 (2015), s. 53-90 ISSN 2055-4877 R&D Projects: GA ČR GAP210/10/1991; GA MŠk LH12041 Institutional support: RVO:67985530 Keywords : carbon isotopes * chemostratigraphy * climate change * Cretaceous * oxygen isotopes Subject RIV: DB - Geology ; Mineralogy

Cellulose and Lignin Carbon Isotope Signatures in Sphagnum Moss Reveal Complementary Environmental Properties

Science.gov (United States)

Loisel, J.; Nichols, J. E.; Kaiser, K.; Beilman, D. W.; Yu, Z.

2016-12-01

The carbon isotope signature (δ13C) of Sphagnum moss is increasingly used as a proxy for past surface wetness in peatlands. However, conflicting interpretations of these carbon isotope records have recently been published. While the water film hypothesis suggests that the presence of a thick (thin) water film around hollow (hummock) mosses leads to less (more) negative δ13C values, the carbon source hypothesis poses that a significant (insignificant) amount of CH4 assimilation by hollow (hummock) mosses leads to more (less) negative δ13C values. To evaluate these competing mechanisms and their impact on moss δ13C, we gathered 30 moss samples from 6 peatlands in southern Patagonia. Samples were collected along a strong hydrological gradient, from very dry hummocks (80 cm above water table depth) to submerged hollows (5 cm below water surface). These peat bogs have the advantage of being colonized by a single cosmopolitan moss species, Sphagnum magellanicum, limiting potential biases introduced by species-specific carbon discrimination. We measured δ13C from stem cellulose and leaf waxes on the same samples to quantify compound-specific carbon signatures. We found that stem cellulose and leaf-wax lipids were both strongly negatively correlated with moss water content, suggesting a primary role of water film thickness on carbon assimilation. In addition, isotopic fractionation during wax synthesis was greater than for cellulose. This offset decreases as conditions get drier, due to (i) a more effective carbon assimilation, or (ii) CH4 uptake through symbiosis with methanotrophic bacteria within the leaves of wet mosses. Biochemical analysis (carbohydrates, amino acids, hydrophenols, cutin acids) of surface moss are currently being conducted to characterize moss carbon allocation under different hydrological conditions. Overall, this modern calibration work should be of use for interpreting carbon isotope records from peatlands.

Constraining the redox landscape of the mid-Proterozoic oceans: new insights from the carbonate uranium isotope record

Science.gov (United States)

Gilleaudeau, G. J.; Kaufman, A. J.; Luo, G.; Romaniello, S. J.; Zhang, F.; Kah, L. C.; Azmy, K.; Bartley, J. K.; Sahoo, S. K.; Knoll, A. H.; Anbar, A. D.

2017-12-01

The redox landscape of the global oceans during the prolonged period between the Great Oxidation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE) is a topic of considerable debate. Data from local redox proxies such as iron speciation suggest largely ferruginous conditions in the subsurface oceans (with the exception of one report of oxic subsurface waters) and a variable degree of euxinia in shallow shelf and epeiric sea environments. There is general consensus that anoxia was more widespread than in the modern ocean, but quantifying the degree of seafloor anoxia is challenging given that most redox proxies are inherently local and/or based on the relatively sparse black shale record. Here, we present new uranium (U) isotope data from carbonate rocks than span the mid-Proterozoic Eon. U-isotopes operate as a proxy for seafloor anoxia because the δ238U value of seawater is largely controlled by the size of the anoxic/euxinic U sink, which preferentially removes isotopically heavy 238U, leaving the oceans enriched in 235U. Our compilation of data from mid-Proterozoic successions reveals δ238U values similar to modern seawater (-0.39 ± 0.19 ‰ [1 s.d.] for the Gaoyuzhuang, Angmaat, El Mreiti, Vazante, and Turukhansk successions spanning 1.5 to 0.9 Ga). Given the potential for an isotopic offset between carbonate minerals and seawater of up to 0.3 ‰, we suggest that mid-Proterozoic seawater had a δ238U value generally between -0.4 and -0.7 ‰, which is lower than modern seawater, but higher than has been inferred for intervals of expanded anoxia elsewhere in Earth history. These results are consistent with recently published U-isotope data from the 1.36 Ga Velkerri Formation, and suggest that large portions of the seafloor may have been covered by at least weakly oxygenated waters during the mid-Proterozoic Eon. Uncertainty remains, however, because the isotopic effects of the non-euxinic anoxic sink are poorly constrained. Nonetheless, our data

Upper Campanian–Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Harlou, Rikke; Schovsbo, Niels

2012-01-01

High-resolution carbon isotope stratigraphy of the upper Campanian – Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower...

Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

Science.gov (United States)

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

1986-01-01

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

Carbon isotope ratios of atmospheric carbon dioxide

International Nuclear Information System (INIS)

Sakai, Hitoshi; Kishima, Noriaki; Tsutaki, Yasuhiro.

1982-01-01

The delta 13 C values relative to PDB were measured for carbon dioxide in air samples collected at various parts of Japan and at Mauna Loa Observatory, Hawaii in the periods of 1977 and 1978. The delta 13 C values of the ''clean air'' are -7.6 % at Hawaii and -8.1 per mille Oki and Hachijo-jima islands. These values are definitely lighter than the carbon isotope ratios (-6.9 per mille) obtained by Keeling for clean airs collected at Southern California in 1955 to 1956. The increase in 12 C in atmospheric carbon dioxide is attributed to the input of the anthropogenic light carbon dioxides (combustion of fossil fuels etc.) Taking -7.6 per mille to be the isotope ratio of CO 2 in the present clean air, a simple three box model predicts that the biosphere has decreased rather than increased since 1955, implying that it is acting as the doner of carbon rather than the sink. (author)

Following Carbon Isotopes from Methane to Molecules

Science.gov (United States)

Freeman, K. H.

2017-12-01

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

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

Science.gov (United States)

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

2008-07-01

isotope fractionation as large as ~ 37‰ appears to characterize the production of bulk organic matter in the deeper part of the Pretoria Basin at that time. This enhanced fractionation relative to that observed in shallow-water environments likely reflects heterotrophic (secondary) and chemotrophic productivity at and below a pronounced redoxcline, consistent with the euxinic conditions inferred from independent evidence for the deeper part of the Pretoria Basin. Greater variability in organic carbon vs. carbonate carbon isotopic values on the shallow-marine carbonate platform suggests that the carbon cycling was dominated by a large dissolved inorganic carbon reservoir during the Lomagundi excursion. Our study suggests that in contrast to the Late Neoproterozoic and Phanerozoic, when carbon isotope fractionation between carbonate and organic carbon in the open ocean was mostly controlled by primary producers, in the Paleoproterozoic redox-stratified ocean heterotrophic and chemotrophic productivity overprinted a signal of primary productivity below the redoxcline. This strong imprint of heterotrophic and chemotrophic productivity on organic carbon isotope records complicates the reconstruction of spatial patterns and secular trends in the δ13C values of dissolved inorganic carbon in the Paleoproterozoic seawater.

Temperature evolution and the oxygen isotope composition of Phanerozoic oceans from carbonate clumped isotope thermometry

Science.gov (United States)

Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Yancey, Thomas E.; Pérez-Huerta, Alberto

2018-05-01

Surface temperature is among the most important parameters describing planetary climate and habitability, and yet there remains considerable debate about the temperature evolution of the Earth's oceans during the Phanerozoic Eon (541 million years ago to present), the time during which complex metazoan life radiated on Earth. Here we critically assess the emerging record of Phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells, and we present new data that fill important gaps in the Late Paleozoic record. We evaluate and reject the hypothesis that solid-state reordering of 13C-18O bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures. The resulting Phanerozoic record, which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide (CO2) levels since the Paleozoic, indicates that tropical temperatures during the icehouse climate of the Carboniferous period were broadly similar to present (∼25-30 °C), and suggests that benthic metazoans were able to thrive at temperatures of 35-40 °C during intervals of the early and possibly the latest Paleozoic when CO2 levels were likely 5-10× higher than present-day values. Equally important, there is no resolvable trend in seawater oxygen isotope ratios (δ18 O) over the past ∼500 million years, indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high (∼270 °C) since at least the early Paleozoic, which points to mid-ocean ridges as the dominant locus of water-rock interaction over the past half-billion years.

Oxygen Isotope Records in Modern Oyster Shells from Chi Ku, Tainan and Their Implication of Seasonality

Science.gov (United States)

Chen, Y. C.; Mii, H. S.; Li, K. T.

2015-12-01

To exam whether oxygen isotope records of Crassostrea gigasoysters can be used as proxies of environment, 133 cultivated oysters and 21 water samples were collected from Chi Ku area, Tainan City, southern Taiwan in December of 2012, and from March, 2013 to July, 2014. Instrumental air and water temperatures and precipitation records were obtained from a nearest Central Weather Bureau (CWB) station roughly 16 km north of Chi Ku. The oxygen and carbon isotope values of the ligamental area of the modern oyster shells are from -6.92‰ to -0.08‰ (-3.05 ± 1.17‰, N = 2280; 1σ; VPDB) and from -5.57‰ to 0.63‰ (-1.88 ± 0.81‰), respectively. Oxygen isotope values of the water samples are mainly between -0.28‰ and 0.74‰ (0.18 ± 0.29‰, N = 20; 1σ; VSMOW). However, water oxygen isotope value of -2.75‰ was observed for the water sample collected immediately after a typhoon heavy rainfall. Seasonal temperature fluctuation pattern of estimated oxygen isotope temperatures from modern shells is similar to that of CWB instrumental records. However, the oxygen isotope temperatures are respectively about 3 °C and 10°C higher than those of instrumental records for winter and summer. Higher estimated oxygen isotope temperatures are most likely caused by underestimated fraction of freshwater. We analyzed 5 archaeological oyster shells of Siraya culture (500~250B.P.) collected from Wu Chien Tuso North (WCTN) archaeological site of Tainan branch of Southern Taiwan Science Park to infer the harvest season of mollusks. Oxygen isotope values of the ligamental area of the archaeological oyster shells are between -5.98‰ and -1.26‰ (-3.34 ± 1.37‰, N = 60; 1σ), and carbon isotope values are between -3.21‰ and 0.60‰ (-2.04‰ ± 0.55‰). The oxygen isotope records of archaeological oyster shells also showed clear seasonality. Most of the oysters were collected in autumn and winter. Oxygen isotope values of archaeological oyster shells was 1‰ greater than that

The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget

Directory of Open Access Journals (Sweden)

Z. Wang

2012-05-01

Full Text Available We present a 60-year record of the stable isotopes of atmospheric carbon monoxide (CO from firn air samples collected under the framework of the North Greenland Eemian Ice Drilling (NEEM project. CO concentration, δ¹³C, and δ¹⁸O of CO were measured by gas chromatography/isotope ratio mass spectrometry (gc-IRMS from trapped gases in the firn. We applied LGGE-GIPSA firn air models (Witrant et al., 2011 to correlate gas age with firn air depth and then reconstructed the trend of atmospheric CO and its stable isotopic composition at high northern latitudes since 1950. The most probable firn air model scenarios show that δ¹³C decreased slightly from −25.8‰ in 1950 to −26.4‰ in 2000, then decreased more significantly to −27.2‰ in 2008. δ¹⁸O decreased more regularly from 9.8‰ in 1950 to 7.1‰ in 2008. Those same scenarios show CO concentration increased gradually from 1950 and peaked in the late 1970s, followed by a gradual decrease to present day values (Petrenko et al., 2012. Results from an isotope mass balance model indicate that a slight increase, followed by a large reduction, in CO derived from fossil fuel combustion has occurred since 1950. The reduction of CO emission from fossil fuel combustion after the mid-1970s is the most plausible mechanism for the drop of CO concentration during this time. Fossil fuel CO emissions decreased as a result of the implementation of catalytic converters and the relative growth of diesel engines, in spite of the global vehicle fleet size having grown several fold over the same time period.

Deciphering Complex Carbon Cycle Changes Across the K-Pg Boundary Using Compound-Specific Carbon Isotopic Analyses

Science.gov (United States)

Pancost, R. D.; Taylor, K. W.; Hollis, C. J.; Crouch, E. M.

2014-12-01

The consequences of the Cretaceous-Paleogene (K/Pg) boundary event on the Earth system have been the subject of much scrutiny. Postulated climate events include a brief (10 - 2000 yr) period of global cooling induced by sulphate aerosols (the so-called 'impact winter'), an interval of warming caused by impact-induced CO2release, as well as longer-term climatic oscillations during the subsequent 1 to 3Myr. Associated with these were putative changes in the biogeochemical cycle, manifested as carbon isotope excursions on both short- and long-term timescales. In this study we develop new biomarker-based climate and biogeochemical records for the mid-Waipara River and Branch Stream sections, NZ. At Branch Stream, a pronounced negative (ca 6 to 8 permil) carbon isotope excursion occurs at the K/Pg; the excursion is recorded by higher plant biomarkers, consistent with some terrestrial records and suggesting that the immediate aftermath of the K/Pg boundary event was characterised by the massive release of 13C-depleted reduced carbon into the ocean-atmosphere reservoir. Mixing across the K/Pg boundary at the Waipara section precludes a similar high-resolution investigation. Lower-resolution, longer-term records, however, also reveal a negative carbon istope excursion documented by both algal and higher plant biomarkers. This event appears to be distinct from that recorded at Branch Stream, being of lower magnitude and longer duration. It coincided with a transient terrestrial and marine warming and appears to have lasted at least 100 kyr and perhaps longer. We argue that this protracted negative CIE reflects a secondary and longer-term consequence of the K/Pg on the global carbon cycle. There is little evidence for an algal extinction as a range of C27 to C30 sterols continued to be deposited throughout the entire section, but changes in GDGT distributions do suggest a change in carbon export dynamics which could have impacted burial of 13C-depleted marine organic matter

Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

DEFF Research Database (Denmark)

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

2015-01-01

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

Paleogene Seawater Osmium Isotope Records

Science.gov (United States)

Rolewicz, Z.; Thomas, D. J.; Marcantonio, F.

2012-12-01

Paleoceanographic reconstructions of the Late Cretaceous and early Cenozoic require enhanced geographic coverage, particularly in the Pacific, in order to better constrain meridional variations in environmental conditions. The challenge with the existing inventory of Pacific deep-sea cores is that they consist almost exclusively of pelagic clay with little existing age control. Pelagic clay sequences are useful for reconstructions of dust accumulation and water mass composition, but accurate correlation of these records to other sites requires improved age control. Recent work indicates that seawater Os isotope analyses provide useful age control for red clay sequences. The residence time of Os in seawater is relatively long compared to oceanic mixing, therefore the global seawater 187Os/188Os composition is practically homogeneous. A growing body of Late Cretaceous and Cenozoic data has constrained the evolution of the seawater Os isotopic composition and this curve is now a viable stratigraphic tool, employed in dating layers of Fe-Mn crusts (e.g., Klemm et al., 2005). Ravizza (2007) also demonstrated that the seawater Os isotopic composition can be extracted reliably from pelagic red clay sediments by analyzing the leached oxide minerals. The drawback to using seawater Os isotope stratigraphy to date Paleogene age sediments is that the compilation of existing data has some significant temporal gaps, notably between ~38 and 55 Ma. To improve the temporal resolution of the seawater Os isotope curve, we present new data from Ocean Drilling Program (ODP) Site 865 in the equatorial Pacific. Site 865 has excellent biostratigraphic age control over the interval ~38-55Ma. Preliminary data indicate an increase in the seawater composition from 0.427 at 53.4 Ma to 0.499 by 43 Ma, consistent with the apparent trend in the few existing data points. We also analyzed the Os isotopic composition recorded by oxide minerals at Integrated Ocean Drilling Program (IODP) Site U1370

Eocene to Oligocene benthic foraminiferal isotopic record in the Bay of Biscay

International Nuclear Information System (INIS)

Miller, K.G.; Curry, W.B.

1982-01-01

Oxygen and carbon isotopic records of Eocene to Oligocene benthic foraminifera from two Bay of Biscay Deep Sea Drilling Project sites are presented. The delta 18 O figures for benthic foraminifera are significantly higher than those previously reported from deeper North Atlantic sites, the differences arising it is believed from diagenetic alteration of the sediments in the deeper-buried sites. (U.K.)

Tempo and scale of late Paleocene and early Eocene carbon isotope cycles: Implications for the origin of hyperthermals

Science.gov (United States)

Zachos, James C.; McCarren, Heather; Murphy, Brandon; Röhl, Ursula; Westerhold, Thomas

2010-10-01

The upper Paleocene and lower Eocene are marked by several prominent (> 1‰) carbon isotope (δ 13C) excursions (CIE) that coincide with transient global warmings, or thermal maxima, including the Paleocene-Eocene Thermal Maximum (PETM). The CIE, which are recorded mainly in marine sedimentary sequences, have also been identified in continental sequences, occurred episodically, and yet appear to be paced or triggered by orbital forcing. To constrain the timing and scale of the CIE relative to long-term baseline variability, we have constructed a 4.52 million year (myr) long, high-resolution (~ 3 kyr) bulk sediment carbon isotope record spanning the lower Eocene to upper Paleocene (C25r-C24n) from a pelagic sediment section recovered at ODP Site 1262 in the southeast Atlantic. This section, which was orbitally-tuned utilizing high-resolution core log physical property and geochemical records, is the most stratigraphically complete upper Paleocene to lower Eocene sequence recovered to date. Time-series analysis of the carbon isotope record along with a high-resolution Fe intensity record obtained by XRF core scanner reveal cyclicity with variance concentrated primarily in the precession (21 kyr) and eccentricity bands (100 and 400-kyr) throughout the upper Paleocene-lower Eocene. In general, minima in δ 13C correspond with peaks in Fe (i.e., carbonate dissolution), both of which appear to be in phase with maxima in eccentricity. This covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity. This relationship includes all late Paleocene and early Eocene CIE confirming pacing by orbital forcing. The lone exception is the PETM, which appears to be out of phase with the 400-kyr cycle, though possibly in phase with the 100-kyr cycle, reinforcing the notion that a mechanism other than orbital forcing and/or an additional source of carbon is required to account for the

Carbon and Oxygen isotopic composition in paleoenvironmental determination

International Nuclear Information System (INIS)

Silva, J.R.M. da.

1978-01-01

This work reports that the carbon and oxygen isotopic composition separate the mollusks from marine environment of the mollusks from continental environment in two groups isotopically different, making the biological control outdone by environment control, in the isotopic fragmentation mechanisms. The patterns from the continental environment are more rich in O 16 than the patterns from marine environments. The C 12 is also more frequent in the mollusks from continental environments. The carbon isotopic composition in paterns from continental environments is situated betwen - 10.31 and - 4,05% and the oxygen isotopic composition is situated between - 6,95 and - 2,41%. To the marine environment patterns the carbon isotopic composition is between - 2,08 and + 2,65% and the oxigen isotopic composition is between - 2,08 and + 0,45%. Was also analysed fossil marine mollusks shells and their isotopic composition permit the formulation of hypothesis about the environment which they lived. (C.D.G.) [pt

Insights into deep-time terrestrial carbon cycle processes from modern plant isotope ecology

Science.gov (United States)

Sheldon, N. D.; Smith, S. Y.

2012-12-01

While the terrestrial biosphere and soils contain much of the readily exchangeable carbon on Earth, how those reservoirs function on long time scales and at times of higher atmospheric CO2 and higher temperatures is poorly understood, which limits our ability to make accurate future predictions of their response to anthropogenic change. Recent data compilation efforts have outlined the response of plant carbon isotope compositions to a variety of environmental factors including precipitation amount and timing, elevation, and latitude. The compilations involve numerous types of plants, typically only found at a limited number of climatic conditions. Here, we expand on those efforts by examining the isotopic response of specific plant groups found both globally and across environmental gradients including: 1) ginkgo, 2) conifers, and 3) C4 grasses. Ginkgo is presently widely distributed as a cultivated plant and the ginkgoalean fossil record spans from the Permian to the present, making it an ideal model organism to understand climatic influence on carbon cycling both in modern and ancient settings. Ginkgo leaves have been obtained from a range of precipitation conditions (400-2200 mm yr-1), including dense sampling from individuals and populations in both Mediterranean and temperate climate areas and samples of different organs and developmental stages. Ginkgo carbon isotope results plot on the global C3 plant array, are consistent among trees at single sites, among plant organs, and among development stages, making ginkgo a robust recorder of both climatic conditions and atmospheric δ13C. In contrast, a climate-carbon isotope transect in Arizona highlights that conifers (specifically, pine and juniper) record large variability between organs and have a very different δ13C slope as a function of climate than the global C3 plant array, while C4 plants have a slope with the opposite sign as a function of climate. This has a number of implications for paleo

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

Science.gov (United States)

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

2017-12-01

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

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

Science.gov (United States)

Schmidt, Gavin A.

1999-01-01

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

The isotope record of short- and long-term dietary changes in sheep tooth enamel: Implications for quantitative reconstruction of paleodiets

Science.gov (United States)

Zazzo, A.; Balasse, M.; Passey, B. H.; Moloney, A. P.; Monahan, F. J.; Schmidt, O.

2010-06-01

Quantitative reconstruction of paleodiet by means of sequential sampling and carbon isotope analysis in hypsodont tooth enamel requires a precise knowledge of the isotopic enrichment between dietary carbon and carbon from enamel apatite ( ɛD-E), as well as of the timing and duration of the enamel mineralization process (amelogenesis). To better constrain these parameters, we performed a series of controlled feeding experiments on sheep ranging in age from 6 to 24 months-old. Twenty-eight lambs and 14 ewes were fed isotopically distinct diets for different periods of time, and then slaughtered, allowing the timing and rate of molar growth to be determined. High resolution sampling and stable carbon isotope analysis of breath CO 2 performed on six individuals following a diet-switch showed that 70-90% of dietary carbon had turned over in less than 24 h. Sequential sampling and carbon isotopic analysis was performed on the first (M 1) and second (M 2) lower molars of four lambs as well as on the third lower molar (M 3) of 11 ewes. The changes in diet were recorded in all molars. We found that the length of enamel matrix apposition is approximately one-quarter of the final tooth length during crown extension, and that enamel maturation spans slightly less than 3 months in M 1, and 4 months in M 2 and M 3. Portions of enamel in equilibrium with dietary carbon were used to calculate ɛD-E values. Animals on grass silage diets had values similar to previous observations, whereas animal switched to pelleted corn diets had values ca. 4‰ lower, a pattern consistent with lower methane production observed for animals fed concentrate diets. The tooth enamel forward model of Passey and Cerling (2002) closely predicted the amplitude of isotope changes recorded in tooth enamel, but slightly underestimated the rate of isotope change, suggesting that the rate of accumulation of carbonate during maturation may not be constant over time. Although stable isotope profiles in tooth

Refining the Neoproterozoic and Early Paleozoic record of carbon cycling and seawater chemistry using quantitative geochemical models of redox dynamics and carbonate diagenesis

DEFF Research Database (Denmark)

Ahm, Anne-Sofie Crüger

based records. Despite the prevalence of diagenesis in sedimentary rocks there are currently few robust geochemical tools capable of providing quantitative information on the extent of alteration from the primary signal. In order to fill this gap, Chapter 3 presents a numerical model of marine carbonate...... through diagenesis and provide more robust estimates for past seawater chemistry. Ancient carbonate rocks with extreme negative carbon isotopes are found worldwide bracketing the Marinoan glaciation (∼635 Ma). There is no scientific consensus as to whether these excursions originate from a primary...... perturbation in the carbon cycle or from diagenetic alterations. Chapter 4 merges new measurements of calcium, magnesium, and strontium isotopes in these sediments with the diagenetic model developed in Chapter 3 to offer new insights into the potential origin of these extreme isotope anomalies....

An experimental study on the effect of carbonic anhydrase on the oxygen isotope exchange kinetics and equilibrium in the carbonic acid system

Science.gov (United States)

Uchikawa, J.; Zeebe, R. E.

2011-12-01

Stable oxygen isotopes of marine biogenic carbonates are often depleted in 18O relative to the values expected for thermodynamic equilibrium with ambient seawater. One possibility is that 18O-depletion in carbonates is kinetically controlled. The kinetic isotope effect associated with the hydration of CO2 results in 18O-depleted HCO3-. If the HCO3- is utilized before re-establishing equilibrium with ambient water under rapid calcification, the 18O-depletion will be recorded in carbonates. But one caveat in this kinetic model is the fact that many marine calcifiers posses carbonic anhydrase, a zinc-bearing enzyme that catalyzes the CO2 hydration reaction. It is expected that this enzyme accelerates 18O-equilibration in the carbonic acid system by facilitating direct oxygen isotope exchange between HCO3- and H2O via CO2 hydration. Clearly this argues against the conceptual framework of the kinetic model. Yet the critical variable here is the effectiveness of the carbonic anhydrase, which is likely to depend on its concentration and the carbonate chemistry of the aqueous medium. It is also hitherto unknown whether the presence of carbonic anhydrase alters the equilibrium oxygen isotope fractionations between dissolved carbonate species and water. We performed a series of quantitative inorganic carbonate precipitation experiments to examine the changes in the oxygen isotope equilibration time as a function of carbonic anhydrase concentrations. We conducted experiments at pH 8.3 and 8.9. These pH values are similar to the average surface ocean pH and the elevated pH levels observed within calcification microenvironments of certain corals and planktonic foraminifera. A summary of our new experimental results will be presented.

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

Science.gov (United States)

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

2017-12-01

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

Gluconeogenesis from labeled carbon: estimating isotope dilution

International Nuclear Information System (INIS)

Kelleher, J.K.

1986-01-01

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

History of Animals using Isotope Records (HAIR): a 6-year dietary history of one family of African elephants.

Science.gov (United States)

Cerling, Thure E; Wittemyer, George; Ehleringer, James R; Remien, Christopher H; Douglas-Hamilton, Iain

2009-05-19

The dietary and movement history of individual animals can be studied using stable isotope records in animal tissues, providing insight into long-term ecological dynamics and a species niche. We provide a 6-year history of elephant diet by examining tail hair collected from 4 elephants in the same social family unit in northern Kenya. Sequential measurements of carbon, nitrogen, and hydrogen isotope rations in hair provide a weekly record of diet and water resources. Carbon isotope ratios were well correlated with satellite-based measurements of the normalized difference vegetation index (NDVI) of the region occupied by the elephants as recorded by the global positioning system (GPS) movement record; the absolute amount of C(4) grass consumption is well correlated with the maximum value of NDVI during individual wet seasons. Changes in hydrogen isotope ratios coincided very closely in time with seasonal fluctuations in rainfall and NDVI whereas diet shifts to relatively high proportions of grass lagged seasonal increases in NDVI by approximately 2 weeks. The peak probability of conception in the population occurred approximately 3 weeks after peak grazing. Spatial and temporal patterns of resource use show that the only period of pure browsing by the focal elephants was located in an over-grazed, communally managed region outside the protected area. The ability to extract time-specific longitudinal records on animal diets, and therefore the ecological history of an organism and its environment, provides an avenue for understanding the impact of climate dynamics and land-use change on animal foraging behavior and habitat relations.

Limnological controls on stable isotope records of late-holocene palaeoenvironment change in sw greenland: A paired lake study

DEFF Research Database (Denmark)

Olsen, Jesper; John Anderson, N.; Leng, M.J.

2013-01-01

Stable isotope records are increasingly being used in palaeoenvironmental studies of Arctic lakes. Here we compare stable isotope and elemental records (δ13C, δ15N, C/N) with high resolution XRF-derived geochemical and colour data from low Arctic lakes (SS1220 and SS85) in southwest Greenland. Lake...... SS1220 sediments are laminated gyttja whereas SS85 consist of homogeneous gyttja, both records cover the last c. 5000 years. d13C and carbon content suggest that organic matter in both lakes is predominantly autochthonous. The C/N variability, ranging between 11 and 15, is interpreted...... composition of lake sediments when there is a reasonable understanding of limnological processes, and records may be lake specific....

Isotopic Recorders of Pollution in Heterogeneous Urban Areas

Science.gov (United States)

Pataki, D. E.; Cobley, L.; Smith, R. M.; Ehleringer, J. R.; Chritz, K.

2017-12-01

A significant difficulty in quantifying urban pollution lies in the extreme spatial and temporal heterogeneity of cities. Dense sources of both point and non-point source pollution as well as the dynamic role of human activities, which vary over very short time scales and small spatial scales, complicate efforts to establish long-term urban monitoring networks that are relevant at neighborhood, municipal, and regional scales. Fortunately, the natural abundance of isotopes of carbon, nitrogen, and other elements provides a wealth of information about the sources and fate of urban atmospheric pollution. In particular, soils and plant material integrate pollution sources and cycling over space and time, and have the potential to provide long-term records of pollution dynamics that extend back before atmospheric monitoring data are available. Similarly, sampling organic material at high spatial resolution can provide "isoscapes" that shed light on the spatial heterogeneity of pollutants in different urban parcels and neighborhoods, along roads of varying traffic density, and across neighborhoods of varying affluence and sociodemographic composition. We have compiled numerous datasets of the isotopic composition of urban organic matter that illustrate the potential for isotopic monitoring of urban areas as a means of understanding hot spots and hot moments in urban atmospheric biogeochemistry. Findings to date already reveal the critical role of affluence, economic activity, demographic change, and land management practices in influencing urban pollution sources and sinks, and suggest an important role of stable isotope and radioisotope measurements in urban atmospheric and biogeochemical monitoring.

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

Science.gov (United States)

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

2015-10-01

types of experiments yielded statistically indistinguishable results, and these measurements yield a calibration that overlaps with our theoretical predictions for calcite at equilibrium. The slow-growing Devils Hole calcite exhibits Δ47 and δ18O values consistent with lattice equilibrium. Factors influencing DIC speciation (pH, salinity) and the timescale for DIC equilibration, as well as reactions at the mineral-solution interface, have the potential to influence clumped-isotope signatures and the δ18O of carbonate minerals. In fast-growing carbonate minerals, solution chemistry may be an important factor, particularly over extremes of pH and salinity. If a crystal grows too rapidly to reach an internal equilibrium (i.e., achieve the value for the temperature-dependent mineral lattice equilibrium), it may record the clumped-isotope signature of a DIC species (e.g., the temperature-dependent equilibrium of HCO3-) or a mixture of DIC species, and hence record a disequilibrium mineral composition. For extremely slow-growing crystals, and for rapidly-grown samples grown at a pH where HCO3- dominates the DIC pool at equilibrium, effects of solution chemistry are likely to be relatively small or negligible. In summary, growth environment, solution chemistry, surface equilibria, and precipitation rate may all play a role in dictating whether a crystal achieves equilibrium or disequilibrium clumped-isotope signatures.

C, Sr and Sr isotopic composition on probable vendian- tommotian carbonate sequences in Nw Argentina

International Nuclear Information System (INIS)

Sial, A. N.; Ferreira, V.P; Toselli, A.J.; Acenolaza, F.G; Pimentel, M.M; Parada, M.A; Alonso, R.N

2001-01-01

C-isotope stratigraphy is one of the most powerfool tools in Precambrian chronostratigraphy, especially when sediments lack recognizable animal fossils. The δ 13 C secular variation curves for marine carbonates in the Neoproterozoic-Cambrian interval show strong positive-negative excursions, several of them interpreted as the stratigraphic position of ancient ice ages (Hoffman et al. 1998). The Sr isotope composition of the seawater for this age interval is characterized by a continuous increase of 87 Sr/ 86 Sr that is interrupted, several times, by sharp rises, which represent important changes in the Earth history (Montanez et al. 2000). Only limited data on the behavior of C and Sr isotopes in carbonates are available in South America. We examine here carbonate sequences from the Argentine Precordillera, San Juan province, and from other carbonate sequences in NW Argentina that could be, potentially, proxies for the Precambrian-Cambrian transition. We have studied their δ 13 C and 87 Sr/ 86 Sr chemostratigraphy and compare it to global C and Sr isotope secular variation curves for this time span. This study aims to improve the relatively coarse stratigraphic resolution provided only by the study of the fossil record in some of the carbonate successions under consideration (au)

Orbital calibration of the late Campanian carbon isotope event in the North Sea

DEFF Research Database (Denmark)

Perdiou, Anastasios; Thibault, Nicolas; Anderskouv, Kresten

2016-01-01

A new record of carbon isotopes, nannofossil biostratigraphy, gamma-ray and Fe content variations is presented for the upper Campanian of the Adda-3 core, Danish Central Graben, North Sea. The studied interval provides a revision of previously assigned late Coniacian to early Santonian ages. New...

Water and carbon stable isotope records from natural archives: a new database and interactive online platform for data browsing, visualizing and downloading

Science.gov (United States)

Bolliet, Timothé; Brockmann, Patrick; Masson-Delmotte, Valérie; Bassinot, Franck; Daux, Valérie; Genty, Dominique; Landais, Amaelle; Lavrieux, Marlène; Michel, Elisabeth; Ortega, Pablo; Risi, Camille; Roche, Didier M.; Vimeux, Françoise; Waelbroeck, Claire

2016-08-01

Past climate is an important benchmark to assess the ability of climate models to simulate key processes and feedbacks. Numerous proxy records exist for stable isotopes of water and/or carbon, which are also implemented inside the components of a growing number of Earth system model. Model-data comparisons can help to constrain the uncertainties associated with transfer functions. This motivates the need of producing a comprehensive compilation of different proxy sources. We have put together a global database of proxy records of oxygen (δ18O), hydrogen (δD) and carbon (δ13C) stable isotopes from different archives: ocean and lake sediments, corals, ice cores, speleothems and tree-ring cellulose. Source records were obtained from the georeferenced open access PANGAEA and NOAA libraries, complemented by additional data obtained from a literature survey. About 3000 source records were screened for chronological information and temporal resolution of proxy records. Altogether, this database consists of hundreds of dated δ18O, δ13C and δD records in a standardized simple text format, complemented with a metadata Excel catalog. A quality control flag was implemented to describe age markers and inform on chronological uncertainty. This compilation effort highlights the need to homogenize and structure the format of datasets and chronological information as well as enhance the distribution of published datasets that are currently highly fragmented and scattered. We also provide an online portal based on the records included in this database with an intuitive and interactive platform (http://climateproxiesfinder.ipsl.fr/), allowing one to easily select, visualize and download subsets of the homogeneously formatted records that constitute this database, following a choice of search criteria, and to upload new datasets. In the last part, we illustrate the type of application allowed by our database by comparing several key periods highly investigated by the

The use of carbon stable isotope ratios in drugs characterization

Energy Technology Data Exchange (ETDEWEB)

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

2013-11-13

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

A carbon isotope budget for an anoxic marine sediment

International Nuclear Information System (INIS)

Boehme, S.E.; Blair, N.E.

1991-01-01

A carbon isotope budget has been determined for the coastal marine site, Cape Lookout Bight, NC. Isotope measurements of methane and σCO 2 fluxing out and buried in these sediments were applied to previously measured flux data (Martens et al., in press) to predict the isotopic composition of the incoming metabolizable organic matter. Methane leaves the sediment predominantly via ebullition with an isotopic composition of -60 per mil. Less than 2% of the methane produced is buried with an average diffusional flux value of -17 per mil and a burial value of +11 per mil. The isotope budget predicts a metabolizable organic carbon isotope signature of -19.3 per mil which is in excellent agreement with the measured total organic carbon value of -19.2 ± 0.3 per mil implying that the dominant remineralization processes have been identified

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

Science.gov (United States)

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

2017-12-19

Carbon isotopes have been widely used in tracing a wide variety of geological and environmental processes. The carbon isotope composition of bulk rocks and minerals was conventionally analyzed by isotope ratio mass spectrometry (IRMS), and, more recently, secondary ionization mass spectrometry (SIMS) has been widely used to determine carbon isotope composition of carbon-bearing solid materials with good spatial resolution. Here, we present a new method that couples a RESOlution S155 193 nm laser ablation system with a Nu Plasma II MC-ICP-MS, with the aim of measuring carbon isotopes in situ in carbonate minerals (i.e., calcite and aragonite). Under routine operating conditions for δ 13 C analysis, instrumental bias generally drifts by 0.8‰-2.0‰ in a typical analytical session of 2-3 h. Using a magmatic calcite as the standard, the carbon isotopic composition was determined for a suite of calcite samples with δ 13 C values in the range of -6.94‰ to 1.48‰. The obtained δ 13 C data are comparable to IRMS values. The combined standard uncertainty for magmatic calcite is ICP-MS can serve as an appropriate method to analyze carbon isotopes of carbonate minerals in situ.

Short-term coral bleaching is not recorded by skeletal boron isotopes.

Science.gov (United States)

Schoepf, Verena; McCulloch, Malcolm T; Warner, Mark E; Levas, Stephen J; Matsui, Yohei; Aschaffenburg, Matthew D; Grottoli, Andréa G

2014-01-01

Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (δ11B), carbon (δ13C), oxygen (δ18O) isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, δ13C and δ18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that reconstruction of

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

Science.gov (United States)

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

2015-01-01

natural systems. The two types of experiments yielded statistically indistinguishable results, and these measurements yield a calibration that overlaps with our theoretical predictions for calcite at equilibrium. The slow-growing Devils Hole calcite exhibits Δ47 and δ18O values consistent with lattice equilibrium.Factors influencing DIC speciation (pH, salinity) and the timescale for DIC equilibration, as well as reactions at the mineral–solution interface, have the potential to influence clumped-isotope signatures and the δ18O of carbonate minerals. In fast-growing carbonate minerals, solution chemistry may be an important factor, particularly over extremes of pH and salinity. If a crystal grows too rapidly to reach an internal equilibrium (i.e., achieve the value for the temperature-dependent mineral lattice equilibrium), it may record the clumped-isotope signature of a DIC species (e.g., the temperature-dependent equilibrium of HCO3−) or a mixture of DIC species, and hence record a disequilibrium mineral composition. For extremely slow-growing crystals, and for rapidly-grown samples grown at a pH where HCO3- dominates the DIC pool at equilibrium, effects of solution chemistry are likely to be relatively small or negligible. In summary, growth environment, solution chemistry, surface equilibria, and precipitation rate may all play a role in dictating whether a crystal achieves equilibrium or disequilibrium clumped-isotope signatures.

Stable isotope ratios in freshwater mussel shells as high resolution recorders of riverine environmental variation

Science.gov (United States)

Kukolich, S.; Kendall, C.; Dettman, D. L.

2017-12-01

The geochemical record stored in growth increments of freshwater mussel shells reveals annual to sub-annual changes in environmental conditions during the lifetime of the organism. The carbon, nitrogen, and oxygen stable isotope composition of aragonite shells responds to changes in water chemistry, temperature, streamflow, turbidity, growth rate, size, age, and reproduction. The goals of this study are to determine how stable isotopes can be used to reconstruct the conditions in which the mussels lived and to illuminate any vital effects that might obscure the isotopic record of those conditions. Previous research has suggested that annual δ13C values decrease in older freshwater mussel shells due to lower growth rates and greater incorporation of dietary carbon into the shell with increasing age. However, a high-resolution, seasonal investigation of δ13C, δ15N, and δ18O as they relate to organism age has not yet been attempted in freshwater mussels. A total of 28 Unionid mussels of three different species were collected live in 2011 in the Tennessee River near Paducah, Kentucky, USA. In this study, we analyzed the shell nacre and external organic layers for stable carbon, nitrogen, and oxygen isotope ratios, focusing on growth bands formed between 2006 and 2011. We present a time series of shell δ13C, δ18O, and δ15N values with monthly resolution. We also compare the shell-derived geochemical time series to a time series of the δ13C and δ15N of particulate organic matter, δ13C of DIC, δ18OWater, and water temperature in which the mussels lived. Results show that environmental factors such as water temperature and primary productivity dominate shell chemistry while animal age has little or no effect.

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

Science.gov (United States)

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

2004-01-01

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

Inheritance of carbon isotope discrimination and water-use efficiency in cowpea

International Nuclear Information System (INIS)

Ismail, A.M.; Hall, A.E.

1993-01-01

Theory has been developed predicting an association between water-use efficiency (WUE = total biomass/transpiration) and leaf discrimination against 13C carbon isotope discrimination which could be used to indirectly select for WUE in C3 plants. Previous studies indicated variation in WUE and carbon isotope discrimination among genotypes of cowpea [Vigna unguiculata (L.) Walp.] and due to drought. Moreover, a highly significant negative correlation between WUE and carbon isotope discrimination was observed for both genotypic and drought effects, as expected based on theory. Present studies were conducted to investigate whether the inheritance of WUE and carbon isotope discrimination is nuclear or maternal, and whether any dominance is present. Contrasting cowpea accessions and hybrids were grown over 2 yr in two outdoor pot experiments, subjected to wet or dry treatments, and under full irrigation in natural soil conditions in 1 yr. Highly significant differences in WUE were observed among cowpea parents and hybrids, and due to drought, which were strongly and negatively correlated with carbon isotope discrimination as expected based on theory. Data from reciprocal crosses indicated that both WUE and carbon isotope discrimination are controlled by nuclear genes. High WUE and low carbon isotope discrimination exhibited partial dominance under pot conditions. In contrast, high carbon isotope discrimination was partially dominant for plants grown under natural soil conditions but in a similar aerial environment as in the pot studies. We speculate that differences in rooting conditions were responsible for the differences in extent of dominance for carbon isotope discrimination of plants growing under pot conditions compared with natural soil conditions in a similar field aerial environment

Carbon and oxygen isotope compositions of the carbonate facies

Indian Academy of Sciences (India)

The Vindhyan sedimentary succession in central India spans a wide time bracket from the Paleopro- terozoic to the Neoproterozoic period.Chronostratigraphic significance of stable carbon and oxygen isotope ratios of the carbonate phase in Vindhyan sediments has been discussed in some recent studies.However,the ...

The organic carbon isotope of lacustrine sediments of the Upper Shahejie formation in Huanghua Depression: a record of sedimentary environment and productivity of an ancient lake

International Nuclear Information System (INIS)

Fei, Weiwei; Huang, Xiaoyan; Dai, Na; Zhong, Ningning

2013-01-01

-rich lamellae is the result of algae blooming and deposition in ancient lakes, as carbonate lamellae is the result of CaCO_3 saturation precipitation with CO_2 decreasing in surface water due to the algal blooming. Lamellar deposition pattern of the mudstone recorded the geological process of algae’s blooming, death and burial. (2) The carbon isotopic composition of organic matter can be a sensitive indicator of the relative significance of bioproductivity and redox conditions as the main factor controlling the formation of organic-rich sediments. δ"1"3C_o_r_g shows a positive correlation with TOC when bioproductivity dominated, however, a negative correlation when redox conditions dominated (Harris et al., 2004). The study on biomarker shows pristane/phytane ratios nearly constant throughout the interval, suggesting the redox environments remained stable. The negative correlation between pristane/phytane ratios and TOC is not obvious, whereas δ"1"3C_o_r_g shows a good positive correlation to TOC%, adjusted R is 0.89. Thus it can be seen that bioproductivity exerted a significant control on organic carbon accumulation in the upper of Shahejie Formation.

Carbon isotope exchange between gaseous CO2 and thin solution films: Artificial cave experiments and a complete diffusion-reaction model

Science.gov (United States)

Hansen, Maximilian; Scholz, Denis; Froeschmann, Marie-Louise; Schöne, Bernd R.; Spötl, Christoph

2017-08-01

Speleothem stable carbon isotope (δ13C) records provide important paleoclimate and paleo-environmental information. However, the interpretation of these records in terms of past climate or environmental change remains challenging because of various processes affecting the δ13C signals. A process that has only been sparsely discussed so far is carbon isotope exchange between the gaseous CO2 of the cave atmosphere and the dissolved inorganic carbon (DIC) contained in the thin solution film on the speleothem, which may be particularly important for strongly ventilated caves. Here we present a novel, complete reaction diffusion model describing carbon isotope exchange between gaseous CO2 and the DIC in thin solution films. The model considers all parameters affecting carbon isotope exchange, such as diffusion into, out of and within the film, the chemical reactions occurring within the film as well as the dependence of diffusion and the reaction rates on isotopic mass and temperature. To verify the model, we conducted laboratory experiments under completely controlled, cave-analogue conditions at three different temperatures (10, 20, 30 °C). We exposed thin (≈0.1 mm) films of a NaHCO3 solution with four different concentrations (1, 2, 5 and 10 mmol/l, respectively) to a nitrogen atmosphere containing a specific amount of CO2 (1000 and 3000 ppmV). The experimentally observed temporal evolution of the pH and δ13C values of the DIC is in good agreement with the model predictions. The carbon isotope exchange times in our experiments range from ca. 200 to ca. 16,000 s and strongly depend on temperature, film thickness, atmospheric pCO2 and the concentration of DIC. For low pCO2 (between 500 and 1000 ppmV, as for strongly ventilated caves), our time constants are substantially lower than those derived in a previous study, suggesting a potentially stronger influence of carbon isotope exchange on speleothem δ13C values. However, this process should only have an

Carbon dioxide effects research and assessment program. Proceedings of the International Meeting on Stable Isotopes in Tree-Ring Research, New Paltz, New York, May 22-25, 1979

Energy Technology Data Exchange (ETDEWEB)

Jacoby, G [ed.

1980-12-01

Information about the past and present concentrations of CO/sub 2/ in the atmosphere and variations in climate can be obtained from measurements of stable isotopes in tree rings; specifically carbon-13, oxygen-18 and deuterium. The analysis of these stable isotopes in tree rings is a relatively new and rapidly developing field. This proceedings volume contains most of the papers presented at the meeting. The first paper gives an overview of the status of carbon-13 research. Papers relating to carbon-13 are in section I and grouped separately from the contributions on carbon-14. Although the meeting was primarily concerned with stable isotopes, all carbon isotopic analysis may be helpful in understanding the carbon-13 record in tree rings. The papers on hydrogen and oxygen isotope studies are in sections II and III respectively. The remaining sections contain papers that consider more than one isotope at a time, general topics related to isotopes, atmospheric changes and tree growth, and methods of isotopic analysis.

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

Science.gov (United States)

Stolper, Daniel A.; Eiler, John M.; Higgins, John A.

2018-04-01

The measurement of multiply isotopically substituted ('clumped isotope') carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample's clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate δ18O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

Influence of chemical structure on carbon isotope composition of lignite

Science.gov (United States)

Erdenetsogt, Bat-Orshikh; Lee, Insung; Ko, Yoon-Joo; Mungunchimeg, Batsaikhan

2017-04-01

During the last two decades, a number of studies on carbon isotopes in terrestrial organic matter (OM) have been carried out and used to determine changes in paleoatmospheric δ13C value as well as assisting in paleoclimate analysis. Coal is abundant terrestrial OM. However, application of its δ13C value is very limited, because the understanding of changes in isotopic composition during coalification is relatively insufficient. The purpose of this study was to examine the influence of the chemical structure on the carbon isotope composition of lignite. Generally, lignite has more complex chemical structures than other higher rank coal because of the existence of various types of oxygen-containing functional groups that are eliminated at higher rank level. A total of sixteen Lower Cretaceous lignite samples from Baganuur mine (Mongolia) were studied by ultimate, stable carbon isotope and solid-state 13C CP/MAS NMR analyses. The carbon contents of the samples increase with increase in depth, whereas oxygen content decreases continuously. This is undoubtedly due to normal coalification process and also consistent with solid state NMR results. The δ13C values of the samples range from -23.54‰ to -21.34‰ and are enriched in 13C towards the lowermost samples. Based on the deconvolution of the NMR spectra, the ratios between carbons bonded to oxygen (60-90 ppm and 135-220 ppm) over carbons bonded to carbon and hydrogen (0-50 ppm and 90-135 ppm) were calculated for the samples. These correlate well with δ13C values (R2 0.88). The results indicate that the δ13C values of lignite are controlled by two mechanisms: (i) depletion in 13C as a result of loss of isotopically heavy oxygen-bounded carbons and (ii) enrichment in 13C caused by a loss of isotopically light methane from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in 13C because the amount of isotopically heavy CO2 and CO, released from coal as a result of changes in the chemical

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

Science.gov (United States)

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

2017-07-01

Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

Isotopes of carbon and oxygen in the carbonate impurities of coal have potential as palaeoenvironmental indicators

International Nuclear Information System (INIS)

Verhagen, B.T.; Falcon, R.M.

1990-01-01

The nature and systematics of impurities such as carbonates need to be established in order to understand their provenance in coal seams with reference to mining, beneficiation and ultimately their elimination or reduction. To this end, mineralogical and carbon-13 and oxygen-18 isotopic studies were undertaken on carbonate occurrences in coal from the eastern Transvaal highveld. Isotopic variations of considerable amplitude and individual values of extreme ''lightness'' are to be found in the carbonates in coal of the Witbank and adjacent basins. The observed isotopic ratios have a clear bearing on the nature and origins of the carbonates. 1 tab., 1 fig

Cerium anomaly across the mid-Tournaisian carbon isotope excursion (TICE)

Science.gov (United States)

Jiang, G.; Morales, D. C.; Maharjan, D. K.

2015-12-01

The Early Mississippian (ca. 359-345 Ma) represents one of the most important greenhouse-icehouse climate transitions in Earth history. Closely associated with this critical transition is a prominent positive carbon isotope excursion (δ13C ≥ +5‰) that has been documented from numerous stratigraphic successions across the globe. This δ13C excursion, informally referred to as the TICE (mid-Tournaisian carbon isotope excursion) event, has been interpreted as resulting from enhanced organic carbon burial, with anticipated outcomes including the lowering of atmospheric CO2 and global cooling, the growth of continental ice sheets and sea-level fall, and the increase of ocean oxygenation and ocean redox changes. The casual relationship between these events has been addressed from various perspectives but not yet clearly demonstrated. To document the potential redox change associated with the perturbation of the carbon cycle, we have analyzed rare earth elements (REE) and trace elements across the TICE in two sections across a shallow-to-deep water transect in the southern Great Basin (Utah and Nevada), USA. In both sections, the REE data show a significant positive cerium (Ce) anomaly (Ce/Ce* = Ce/(0.5La+0.5Pr)). Prior to the positive δ13C shift, most Ce/Ce* values are around 0.3 (between 0.2 and 0.4). Across the δ13C peak, Ce/Ce* values increase up to 0.87, followed by a decrease back to 0.2~0.3 after the δ13C excursion (Figure 1). The positive Ce anomaly is best interpreted as recording expansion of oxygen minimum zone and anoxia resulted from increased primary production. This is consistent with a significant increase of nitrogen isotopes (δ15N) across the δ13C peak. Integration of the carbon, nitrogen, and REE data demonstrates a responsive earth systems change linked to the perturbation of the Early Mississippian carbon cycle.

Short-term measurement of carbon isotope fractionation in plants

International Nuclear Information System (INIS)

O'Leary, M.H.; Treichel, I.; Rooney, M.

1986-01-01

Combustion-based studies of the carbon-13 content of plants give only an integrated, long-term value for the isotope fractionation associated with photosynthesis. A method is described here which permits determination of this isotope fractionation in 2 to 3 hours. To accomplish this, the plant is enclosed in a glass chamber, and the quantity and isotopic content of the CO 2 remaining in the atmosphere are monitored during photosynthesis. Isotope fractionation studies by this method give results consistent with what is expected from combustion studies of C 3 , C 4 , and Crassulacean acid metabolism plants. This method will make possible a variety of new studies of environmental and species effects in carbon isotope fractionation

High-resolution carbon dioxide concentration record 650,000-800,000 years before present

DEFF Research Database (Denmark)

Lüthi, Dieter; Le Floch, Martine; Bereiter, Bernhard

2008-01-01

Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650......,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide...... is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16...

Using n-alkane records to constrain carbon cycle - hydrological cycle coupling: Case study from the Northern Hemisphere mid-latitudes during the PETM

Science.gov (United States)

Krishnan, S.; Pagani, M.; Tipple, B. J.

2010-12-01

The early Eocene was a warmer world compared to the present and is characterized by rising temperatures interspersed with rapid hyperthermal events. During the largest of these rapid warming events; the Paleocene-Eocene Thermal Maximum (PETM), proxy records suggest that sea surface temperatures (SST) rose by 3-5 deg. C in the tropics (Zachos et al., 2003, Tripati and Elderfield, 2004), >5 deg. C in the Arctic (Sluijs et al., 2006) and perhaps has high as 9 deg. C in some sub-Antarctic regions (Kennett and Stott, 1991; Thomas et al., 1999). This warming is believed to be the result of massive input of 13C-depleted carbon into the ocean-atmosphere system, evidenced by the large negative carbon isotope excursion (CIE) and carbonate dissolution associated with the event. However, there are several questions regarding the exact mechanism of warming and feedbacks between the carbon cycle and climate. Did climate shift prior to the main event that led to the release of isotopically light carbon? Do we observe consistent leads or lags between changes in carbon isotopes and hydrological conditions during warm intervals? This study aims to reconstruct hydrological changes in the in the Northern Hemisphere mid-latitudes during the PETM using terrestrial biomarkers. Terrestrial biomarkers, such leaf-wax lipids stored in sediments, have the unique advantage of recording carbon and hydrogen isotopic compositions of atmospheric CO2 (modified by plant fractionation) and precipitation (modified by plant fractionation and evapotranspiration), allowing evaluation of the relative timing of carbon and hydrogen isotopic (i.e., climate) shifts. In this study, we compile and present three mid-latitude PETM records from the Northern Hemisphere, i.e. Alamedilla (Spain), Cicogna and Forada (Italy). The Cicogna and Forada sections are located in the Belluno basin (~12 km apart). Preliminary results do not indicate any significant pre-excursion hydrogen isotope changes at Cicogna, while at

Major events in Neogene oxygen isotopic records

International Nuclear Information System (INIS)

Kennett, J.P.; Hodell, D.A.

1986-01-01

Changes in oxygen isotopic ratios of foraminiferal calcite during the cainozoic have been one of the primary tools for investigating the history of Arctic and Antarctic glaciation, although interpretations of the oxygen isotopic record differ markedly. The ambiguity in interpretation results mainly from the partitioning of temperature from ice volume effects in delta 18 O changes. Oxygen isotopic records for the Cainozoic show an increase in delta 18 O values towards the present, reflecting gradual cooling and increased glaciation of the Earth's climate since the late Cretaceous. A variety of core material from the South Atlantic and South-west Pacific oceans are investigated. This composite data represents one of the most complete available with which to evaluate the evolution of glaciation during the Neogene. Expansion of ice shelves in Antarctica undoubtedly accompanied the increased glaciation of the northern hemisphere, since eustatic sea-level lowering would positively reinforce ice growth on Antarctica

Carbon, hydrogen oxygen isotope studies on imbedded old tree ring and paleoclimate reconstruction

International Nuclear Information System (INIS)

Sun Yanrong; Mu Zhiguo; Cui Haiting

2002-01-01

Tree ring is a kind of natural archives, on which the isotopic analysis is important to study global climate and environmental change. The authors mainly provide a comprehensive introduction to the fractionation models of carbon, hydrogen and oxygen isotope in plants, their research technique and the extract methods from cellulose. That results show isotopic tracer can record the message of climatic variation and has become a powerful tool for paleoclimate reconstruction and for the modern environment changing research. Especially studying on PAGES. the cellulose isotopic analyses of imbedded old tree ring have become the mainly quantitative means of environmental evolvement. In addition, China is a typical monsoon country, research in tree ring stable isotope seasonal variation can give a lot of important information on that. Up to now, the research techniques and works on tree ring in China are still in its earlier stage, and remain many limitations. It needs further accumulate basic research materials, intensity regional contrast and intercross studies on relative subjects

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

Directory of Open Access Journals (Sweden)

D. Codron

2005-06-01

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

Toward explaining the Holocene carbon dioxide and carbon isotope records: Results from transient ocean carbon cycle-climate simulations

Science.gov (United States)

Menviel, L.; Joos, F.

2012-03-01

The Bern3D model was applied to quantify the mechanisms of carbon cycle changes during the Holocene (last 11,000 years). We rely on scenarios from the literature to prescribe the evolution of shallow water carbonate deposition and of land carbon inventory changes over the glacial termination (18,000 to 11,000 years ago) and the Holocene and modify these scenarios within uncertainties. Model results are consistent with Holocene records of atmospheric CO2 and δ13C as well as the spatiotemporal evolution of δ13C and carbonate ion concentration in the deep sea. Deposition of shallow water carbonate, carbonate compensation of land uptake during the glacial termination, land carbon uptake and release during the Holocene, and the response of the ocean-sediment system to marine changes during the termination contribute roughly equally to the reconstructed late Holocene pCO2 rise of 20 ppmv. The 5 ppmv early Holocene pCO2 decrease reflects terrestrial uptake largely compensated by carbonate deposition and ocean sediment responses. Additional small contributions arise from Holocene changes in sea surface temperature, ocean circulation, and export productivity. The Holocene pCO2 variations result from the subtle balance of forcings and processes acting on different timescales and partly in opposite direction as well as from memory effects associated with changes occurring during the termination. Different interglacial periods with different forcing histories are thus expected to yield different pCO2 evolutions as documented by ice cores.

Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

International Nuclear Information System (INIS)

Ivlev, A.A.; Kaloshin, A.G.; Koroleva, M.Ya.

1982-01-01

The analysis of the carbon isotope distribution in carbohydrates and amino acids of some photosynthesizing organisms revealed the close relationship between distribution and the pathways of biosynthesis of the molecules. This relationship is explained on the basis of the previously proposed mechanism of carbon isotope fractionation in a cell, in which the chief part is played by kinetic isotope effects in the pyruvate decarboxylation reaction progressively increased in the conjugated processes of gluconeogenesis. Isotope differences of C 2 and C 3 fragments arising in decarboxylation of pyruvate, as well as isotope differences of biogenic acceptor and environmental CO 2 appearing in assimilation are the main reasons of the observed intramolecular isotopic heterogeneity of biomolecules. The heterogeneity is preserved in metabolites owing to an incomplete mixing of carbon atoms in biochemical reactions. The probable existence of two pools of carbohydrates in photosynthesizing organisms different in isotopic composition is predicted. Two types of intramolecular isotope distribution in amino acids are shown. (author)

Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

Energy Technology Data Exchange (ETDEWEB)

Ivlev, A.A.; Kaloshin, A.G.; Koroleva, M.Ya. (Ministerstvo Geologii SSR, Moscow)

1982-02-10

The analysis of the carbon isotope distribution in carbohydrates and amino acids of some photosynthesizing organisms revealed the close relationship between distribution and the pathways of biosynthesis of the molecules. This relationship is explained on the basis of the previously proposed mechanism of carbon isotope fractionation in a cell, in which the chief part is played by kinetic isotope effects in the pyruvate decarboxylation reaction progressively increased in the conjugated processes of gluconeogenesis. Isotope differences of C/sub 2/ and C/sub 3/ fragments arising in decarboxylation of pyruvate, as well as isotope differences of biogenic acceptor and environmental CO/sub 2/ appearing in assimilation are the main reasons of the observed intramolecular isotopic heterogeneity of biomolecules. The heterogeneity is preserved in metabolites owing to an incomplete mixing of carbon atoms in biochemical reactions. The probable existence of two pools of carbohydrates in photosynthesizing organisms different in isotopic composition is predicted. Two types of intramolecular isotope distribution in amino acids are shown.

Carbon and oxygen stable isotope and trace element studies in speleothems and across the J-K boundary, Central Italy

International Nuclear Information System (INIS)

Kudielka, G.

2001-07-01

Carbon and Oxygen stable isotope ratios of carbonates decisively depend on fractionation during physicochemical processes. Therefore, they represent a powerful tool to derive information on past conditions under which the carbonates formed. Isotope ratio mass spectrometry (IRMS) offers a large range of applications. This thesis presents two projects based upon investigation of carbon and oxygen stable isotope ratios combined with trace element abundances (determined by instrumental neutron activation analysis, INAA) in carbonates. (1) Palaeoclimatic investigation on speleothems from central Italy. Four speleothems from Grotta Grande del Vento, central Italy, were analyzed for stable isotope ratios and trace element abundances, and age dated to obtain a chronologically reliable stable isotope profile. The speleothems were sampled by means of a dental drill to gain a stable isotope profile with a 0.5 mm resolution, trace element abundances have been performed by INAA every 0.5 cm, and the samples for age dating were picked according to remarkable features in the stable isotope trends and analyzed by TIMS. The record covers the period from 93 ka until the early holocene with a hiatus lasting from 75 ka until 65.0 ka. Speleothem growth during the last glacial indicates moderate conditions in the Frasassi region back then. Comparison with speleothems from Ireland, France and northern Italy reveal a north-south slope in d18O, indicating, that the rain over central Italy mainly originates from the North Atlantic. Depletion of moisture in d18O during its continental trajectory is due to rainout, which primarily extracts the heavy isotopes. The stable isotope record is in good agreement with the high-resolution speleothem record from Soreq Cave, Israel. Distinct isotopic events coincide between 85 ka and 80 ka, between ∼ 60 ka and 50 ka and from the last glacial to the early holocene. An offset has been existing between the two records at any time. The speleothems of

Carbon isotope chemostratigraphy of the Llandovery in northern peri-Gondwana: new data from the Barrandian area, Czech Republic

Directory of Open Access Journals (Sweden)

Jiří Frýda

2014-12-01

Full Text Available The first complete δ13Corg record of the uppermost Hirnantian to lower Telychian strata of the Barrandian area (northern peri-Gondwana is presented based on 168 new samples. The new data from the study area reveal that the evolution of the Llandoverian organic carbon isotope reservoir was similar to that on other palaeoplates, but it differs from the development of the coeval carbonate carbon isotope reservoir in the absence of two δ13C excursions (i.e. the early Aeronian positive excursion in the upper part of the Demirastrites triangulatus graptolite Biozone and a negative excursion occurring close to the boundary between the Cystograptus vesiculosus and Coronograptus cyphus graptolite biozones.

Measurement of stable isotope ratio of organic carbon in water samples

International Nuclear Information System (INIS)

Fujii, Toshihiro; Otsuki, Akira

1977-01-01

A new method for the measurement of stable isotope ratios was investigated and applied to organic carbon's isotope ratio measurements in water samples. A few river water samples from Tsuchiura city were tested. After the wet oxidation of organic carbons to carbon dioxide in a sealed ampoule, the isotope ratios were determined with the gas chromatograph-quadrupole mass spectrometer combined with a total organic carbon analyser, under the dynamic conditions. The GC-MS had been equipped with the multiple ion detector-digital integrator system. The ion intensities at m/e 44 and 45 were simultaneously measured at a switching rate of 1 ms. The measurements with carbon dioxide acquired from sodium carbonate (53 μg) gave the isotope ratios with the variation coefficient of 0.62%. However, the variation coefficients obtained from organic carbons in natural water samples were 2 to 3 times as high as that from sodium carbonate. This method is simple and rapid and may be applied to various fields especially in biology and medicine. (auth.)

Multiscale Organization and Isotopic Composition of Carbons in Acapulco and Lodran as Fingerprints of Their Parent Body Story

Science.gov (United States)

Charon, E.; Aléon, J.; Rouzaud, J. N.

2012-09-01

New structural and isotopic data recorded on carbon components of Acapulco and Lodran meteorites allow to propose a scenario of their parent body thermal story, with an impact induced introduction of CI-CM like IOM.

Stable-carbon isotope variability in tree foliage and wood

International Nuclear Information System (INIS)

Leavitt, S.W.; Long, A.

1986-01-01

This study documents variation of stable-carbon isotope ratios ( 13 C/ 12 C) in trees of genera Juniperus and Pinus under field conditions. Results are from cellulose analysis on leaves, twigs, and wood from a number of localities in the southwestern US. Substantial variability, typically 1-3%, exists among leaves, within wood (radially, vertically, circumferentially), and between individuals at a site. These results may help guide sampling in tracer-type studies with stable-carbon isotope ratios and aid in the interpretation of isotopic results from such studies

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-06-15

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

Chromium isotope fractionation during coprecipitation with calcium carbonate

DEFF Research Database (Denmark)

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

The chromium (Cr) isotopic composition of carbonates can potentially be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenvironmental changes, for example related to the rise of oxygen during the Ar...... et al., 2007, Water Air Soil Poll. 179, 381-390. [2] Sánchez-Pastor et al., 2011, Cryst. Growth Des. 11, 3081-3089.......The chromium (Cr) isotopic composition of carbonates can potentially be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenvironmental changes, for example related to the rise of oxygen during...... the Archaean and Protoerozoic, needs careful assessment of the signal robustness and necessitates a thorough understanding of the Cr cycle in Earth system processes. We conducted experiments testing the incorporation and isotopic fractionation of chromate into the calcite lattice. Our experiments indicate...

Carbon and nitrogen isotopic signatures of bat guanos as record of past environments

International Nuclear Information System (INIS)

Mizutani, Hiroshi; Kabaya, Yuko; McFarlane, D.A.

1992-01-01

Carbon and nitrogen isotope ratios were measured for various ecogeochemical samples relevant to bat guano ecosystems. In particular, ca. 800-year-old subfossil guano from Jackson's Bay Cave Compex, Jamaica, yielded ratios similar to the modern guano from other Jamaican bat caves but quite different from modern guano of the same area. Diagenetic change and differences in bat food habits were unlikely explanations for the observation. Instead, insects that feed on C 4 and CAM plants were the main prey for the bats in present Jackson's Bay area, while the ultimate source of organic matter for bats in other Jamaican caves and for the bats that deposited guano in Jackson's Bay Great Cave ca. 800 years ago were C 3 photosynthesis. We suggests that the isotopic data indicate that the surrounding environment experienced a significant mesic episode in the recent past. This mesic climate would have supported a large population of bats, which in turn would have accumulated significant quantities of guano. The subsequent return to the more xeric conditions prevailing today would have caused a drastic reduction in bat population size and effectively ended significant guano accumulation. Fossil guano from Carlsbad Caverns, New Mexico, U.S.A., suggested that native C 3 plants might have been more abundant in Wisconsinan than today. Isotope analyses of old guanos from Bat Cave in Grand Canyon National Park, Arizona, U.S.A., found a possible implication that C 4 photosynthesis might have had contributed a little more to the bats' diet in the cave before the construction of Glen Canyon Dam. (author)

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

Science.gov (United States)

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

2011-12-01

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

Robust optical carbon dioxide isotope analyzer, Phase I

Data.gov (United States)

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

Compound-specific carbon isotopes from Earth’s largest flood basalt eruptions directly linked to the end-Triassic mass extinction

Science.gov (United States)

Whiteside, Jessica H.; Olsen, Paul E.; Eglinton, Timothy; Brookfield, Michael E.; Sambrotto, Raymond N.

2010-01-01

A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO2. The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie’s Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO2 super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date. PMID:20308590

Characteristics of stable carbon isotopic composition of shale gas

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Zhenya Qu

2016-04-01

Full Text Available A type Ⅱ kerogen with low thermal maturity was adopted to perform hydrocarbon generation pyrolysis experiments in a vacuum (Micro-Scale Sealed Vessel system at the heating rates of 2 °C/h and 20 °C/h. The stable carbon isotopic compositions of gas hydrocarbons were measured to investigate their evolving characteristics and the possible reasons for isotope reversal. The δ13C values of methane became more negative with the increasing pyrolysis temperatures until it reached the lightest point, after which they became more positive. Meanwhile, the δ13C values of ethane and propane showed a positive trend with elevating pyrolysis temperatures. The carbon isotopic compositions of shale gasses were mainly determined by the type of parent organic matter, thermal evolutionary extent, and gas migration in shale systems. Our experiments and study proved that the isotope reversal shouldn't occur in a pure thermogenic gas reservoir, it must be involved with some other geochemical process/es; although mechanisms responsible for the reversal are still vague. Carbon isotopic composition of the Fayetteville and Barnett shale gas demonstrated that the isotope reversal was likely involved with water–gas reaction and Fischer-Tropsch synthesis during its generation.

Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

Science.gov (United States)

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

2013-12-01

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

Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

International Nuclear Information System (INIS)

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

2007-01-01

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

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

Science.gov (United States)

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

2016-02-01

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

Temperature dependence of carbon isotope fractionation in CAM plants

International Nuclear Information System (INIS)

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

1985-01-01

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

Temperature dependence of carbon isotope fractionation in CAM plants

Energy Technology Data Exchange (ETDEWEB)

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

1985-09-01

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

Century-scale high-resolution black carbon records in sediment cores from the South Yellow Sea, China

Science.gov (United States)

Xu, Xiaoming; Hong, Yuehui; Zhou, Qianzhi; Liu, Jinzhong; Yuan, Lirong; Wang, Jianghai

2018-01-01

Black carbon (BC) has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance, preserving fire-history records, and more importantly, acting as an indicator of biogeochemical cycles and global changes. By adopting an improved chemothermal oxidation method (WXY), this study reconstructed the century-scale high-resolution records of BC deposition from two fine-grained sediment cores collected from the Yellow Sea Cold Water Mass in the South Yellow Sea. The BC records were divided into five stages, which exhibited specific sequences with three BC peaks at approximately 1891, 1921, and 2007 AD, representing times at which the first heavy storms appeared just after the termination of long-term droughts. The significant correlation between the times of the BC peaks in the cores and heavy storms in the area of the Huanghe (Yellow) River demonstrated that BC peaks could result from markedly strengthened sedimentation due to surface runoff, which augmented the atmospheric deposition. Stable carbon isotope analysis indicated that the evident increase in carbon isotope ratios of BC in Stage 5 might have resulted from the input of weathered rock-derived graphitic carbon cardinally induced by the annual anthropogenic modulation of water-borne sediment in the Huanghe River since 2005 AD. Numerical calculations demonstrated that the input fraction of graphitic carbon was 22.97% for Stage 5, whereas no graphitic carbon entered during Stages 1 and 3. The obtained data provide new and important understanding of the source-sink history of BC in the Yellow Sea.

Absorption of carbon dioxide and isotope exchange rate of carbon in a reaction system between carbon dioxide and carbamic acid

International Nuclear Information System (INIS)

Takeshita, Kenji; Kitamoto, Asashi

1985-01-01

The performance of isotope separation of carbon-13 by chemical exchange between carbon dioxide and carbamic acid was studied. The working fluid used in the study was a solution of DNBA, (C 4 H 9 ) 2 NH and n-octane mixture. Factors related to the isotope exchange rate were measured, such as the absorption rate of carbon dioxide into the solution of DNBA and n-octane, the isotope exchange rate and the separation factor in the reaction between CO 2 and carbamic acid. The absorption of CO 2 into the working fluid was the sum of chemical absorption by DNBA and physical absorption by n-octane. The absorption of carbon dioxide into the working fluid was negligible at temperatures over 90 0 C, but increased gradually at lower temperatures. Carbon dioxide was absorbed into DNBA by chemical absorption, and DNBA was converted to carbamic acid by the reaction. The reaction for synthesis and decomposition of carbamic acid was reversible. The separation factor in equilibrium reached a large value at lower temperatures. The isotope exchange rate between gas and liquid was proportional to the product of the concentration of carbamic acid and the concentration of CO 2 by physical absorption. The isotope separation of carbon by chemical exchange reaction is better operated under the conditions of lower temperature and higher pressure. (author)

Stable carbon isotope fractionation in pollen of Atlas cedar: first steps towards a new palaeoecological proxy for Northwest Africa

Science.gov (United States)

Bell, Benjamin; Fletcher, William; Ryan, Peter; Grant, Helen; Ilmen, Rachid

2016-04-01

Analysis of stable carbon isotopes can provide information on climate and the environmental conditions at different growth stages of the plant, both past and present. Carbon isotope discrimination in plant tissue is already well understood, and can be used as a drought stress indicator for semi-arid regions. Stable carbon isotope ratios measured directly on pollen provides the potential for the development of long-term environmental proxies (spanning thousands of years), as pollen is well preserved in the environment. Atlas Cedar (Cedrus atlantica Endl. Manetti ex Carrière), is an ideal test case to develop a pollen stable carbon isotope proxy. The tree grows across a wide altitudinal and climatic range and is extremely sensitive to moisture availability. The pollen is abundant, and easily identifiable to the species level in pollen analysis because different cedar species are geographically confined to different regions of the world. In 2015 we sampled 76 individual cedar trees across latitudinal, altitudinal and environmental gradients, highly focused on the Middle Atlas region of Morocco, with 25 additional samples from botanical gardens across Europe and the US to extend these gradients. Here, we report new stable carbon isotope data from pollen, leaf and stem wood from these samples with a view to assessing and quantifying species-specific fractionation effects associated with pollen production. The isotopic response of individual trees at local and wider geographical scales to altitude and climatic conditions is presented. This research forms part of an ongoing PhD project working to develop and calibrate a modern carbon isotope proxy in Atlas cedar pollen, which can ultimately be applied to fossil sequences and complement existing multi-proxy records (e.g. pollen analysis in lake sediments, tree-rings).

High-resolution carbon dioxide concentration record 650,000-800,000 years before present

Energy Technology Data Exchange (ETDEWEB)

Luthi, D; Bereiter, B; Blunier, T; Siegenthaler, U; Kawamura, K; Stocker, T F [Climate and Environm. Physics, Physics Inst., Univ. Bern, CH-3012 Bern, (Switzerland); Luthi, D; Bereiter, B; Blunier, T; Siegenthaler, U; Kawamura, K; Stocker, T F [Oeschger Centre for Climate Change Research, Univ. Bern, CH-3012 Bern, (Switzerland); Le Floch, M; Barnola, J M; Raynaud, D [LGGE, CNRS-Univ. Grenoble 1, F-38402 Saint Martin d' Heres, (France); Jouzel, J [Inst. Pierre Simon Laplace, LSCE, CEA-CNRS-Universite Versailles-Saint Quentin, CEA Saclay, F-91191 Gif sur Yvette (France); Fischer, H [Alfred Wegener Inst. for Polar and Maine Research, D-27568 Bremerhaven, (Germany)

2008-07-01

Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172-300 p.p.m.v. (authors)

Ca and Sr isotope records support ocean acidification during end-Permian mass extinction

Science.gov (United States)

Wang, J.; Jacobson, A. D.; Zhang, H.; Ramezani, J.; Sageman, B. B.; Hurtgen, M.; Bowring, S. A.; Shen, S.

2017-12-01

The end-Permian mass extinction represents the most devastating loss of biodiversity during the Phanerozoic. A negative carbon isotope (δ13C) excursion that accompanies the event suggests a significant perturbation to the global carbon cycle, likely induced by CO2 emissions during eruption of the Siberian Traps large igneous province. The carbon cycle is linked with the Ca and Sr cycles through chemical weathering and carbonate precipitation. Therefore, analyses of Ca (δ44/40Ca), radiogenic Sr (87Sr/86Sr), and stable Sr (δ88/86Sr) isotope abundance variations in marine carbonate rocks spanning the Permian-Triassic Boundary (PTB) can reveal key information about biogeochemical changes that occurred during this time. We report δ44/40Ca, 87Sr/86Sr, and δ88/86Sr records analyzed by TIMS for the Meishan and Dajiang sections in China. δ44/40Ca values exhibit similar patterns in both sections. The values remain unchanged across the extinction event layer (EXT) and then decrease by 0.20‰ before increasing by 0.20‰ to 0.40‰ around the PTB. In the Meishan section, 87Sr/86Sr ratios increase after the EXT and return to pre-excursion levels by the PTB. Simultaneously, δ88/86Sr values decrease by 0.12‰ across the EXT and increase by 0.08‰ by the PTB. The patterns of our data support the hypothesis that elevated atmospheric CO2 levels enhanced chemical weathering inputs and might have caused transient ocean acidification, with an "alkalinity overshoot" and increased carbonate deposition occurring after the extinction. Additional measurements and model calculations are underway to help refine and improve these preliminary interpretations.

Modeling of the global carbon cycle - isotopic data requirements

International Nuclear Information System (INIS)

Ciais, P.

1994-01-01

Isotopes are powerful tools to constrain carbon cycle models. For example, the combinations of the CO 2 and the 13 C budget allows to calculate the net-carbon fluxes between atmosphere, ocean, and biosphere. Observations of natural and bomb-produced radiocarbon allow to estimate gross carbon exchange fluxes between different reservoirs and to deduce time scales of carbon overturning in important reservoirs. 18 O in CO 2 is potentially a tool to make the deconvolution of C fluxes within the land biosphere (assimilation vs respirations). The scope of this article is to identify gaps in our present knowledge about isotopes in the light of their use as constraint for the global carbon cycle. In the following we will present a list of some future data requirements for carbon cycle models. (authors)

Methane clumped isotopes: Progress and potential for a new isotopic tracer

Energy Technology Data Exchange (ETDEWEB)

Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.; Sessions, Alex L.; Lawson, Michael; Shuai, Yanhua; Bishop, Andrew; Podlaha, Olaf G.; Ferreira, Alexandre A.; Santos Neto, Eugenio V.; Niemann, Martin; Steen, Arne S.; Huang, Ling; Chimiak, Laura; Valentine, David L.; Fiebig, Jens; Luhmann, Andrew J.; Seyfried, William E.; Etiope, Giuseppe; Schoell, Martin; Inskeep, William P.; Moran, James J.; Kitchen, Nami

2017-11-01

The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.

Carbon isotope fractionation between amorphous calcium carbonate and calcite in earthworm-produced calcium carbonate

International Nuclear Information System (INIS)

Versteegh, E.A.A.; Black, S.; Hodson, M.E.

2017-01-01

In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO_3. Initially a milky fluid comprising micro-spherules of amorphous CaCO_3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-spherules coalesce and crystalize to form millimetre scale granules, largely comprising calcite. These are secreted into the earthworm intestine and from there into the soil. L. terrestris were cultured for 28 days in two different soils, moistened with three different mineral waters at 10, 16 and 20 °C. The milky fluid in the calciferous glands, granules in the pouches of the calciferous glands and granules excreted into the soil were collected and analysed by FTIR spectroscopy to determine the form of CaCO_3 present and by IRMS to determine δ"1"3C values. The milky fluid was ACC. Granules removed from the pouches and soil were largely calcite; the granules removed from the pouches contained more residual ACC than those recovered from the soil. The δ"1"3C values of milky fluid and pouch granules became significantly more negative with increasing temperature (p ≤ 0.001). For samples from each temperature treatment, δ"1"3C values became significantly (p ≤ 0.001) more negative from the milky fluid to the pouch granules to the soil granules (−13.77, −14.69 and −15.00 respectively at 10 °C; −14.37, −15.07 and −15.18 respectively at 16 °C and −14.89, −15.41 and −15.65 respectively at 20 °C). Fractionation of C isotopes occurred as the ACC recrystallized to form calcite with the fractionation factor ε_c_a_l_c_i_t_e_-_A_C_C = −1.20 ± 0.52‰. This is consistent with the crystallization involving dissolution and reprecipitation rather than a solid state rearrangement. Although C isotopic fractionation has previously been described between different species of dissolved inorganic carbon

Forensic utility of the carbon isotope ratio of PVC tape backings

Science.gov (United States)

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

2008-12-01

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

The dynamics of CO2 fixation in the Southern Ocean as indicated by carboxylase activities and organic carbon isotopic ratios

International Nuclear Information System (INIS)

Fontugne, M.

1991-01-01

Recent studies have suggested a direct relationship between the dissolved CO 2 concentration and carbon isotopic composition of phytoplankton in surface ocean. Thus, measurement of δ 13 C of planktonic organic matter in deep-sea ocean cores can potentially yield a record of the past atmospheric CO 2 variations. However, results are presented from 3 cruises in Indian and Atlantic sectors of the Southern Ocean (between 40-66degS) in which biochemical and physiological factors associated with photosynthetic processes lead to carbon isotopic fractionation by phytoplankton which cannot be directly related to variations within the mineral carbon pool. Simultaneous measurements of the carboxylase activities in the 13 C/ 12 C ratio of particulate organic carbon show that there is a large variability in phytoplankton carbon metabolism, especially on a seasonal scale, in spite of a relative uniformity of the environmental conditions. Phytoplankton carbon metabolism is clearly a main factor governing variations in the stable isotopic composition of organic matter in the euphotic layer. Interrelationships between light, Rubiso activity and δ 13 C are clearly shown by the data. Heterotrophic processes may also influence the carbon isotope mass balance, especially during the break-up of the ice pack. In addition to the influence of photosynthetic metabolism, the effect of the meridoneal temperature gradient is also verified by the data set. (author). 24 refs.; 5 figs

Paradox of the peak-PCIM (Paleocene Carbon Isotope Maxima; ~57.8Ma) and Abrupt Global Warming

Science.gov (United States)

Harper, D. T.; Hoenisch, B.; Zachos, J. C.

2015-12-01

The Paleocene Carbon Isotope Maxima (PCIM; ~57.8Ma) represents a major transition in global δ13C during the late Paleocene, when the long-term positive trend in δ13C reversed from positive to negative. The peak-PCIM (~57.7Ma) has been tightly resolved in new high-resolution, astronomically-tuned benthic isotope records from IODP Sites 1209 (Pacific) and 1262 (Atlantic), which show the final phase of δ13C enrichment as abrupt (~1‰ in paradox as any rapid carbon release to the atmosphere should, in theory, create a negative excursion because all of the major carbon sources are isotopically light, whether volcanic outgassing, weathering/oxidation of organic carbon, or methane release [Dunkley-Jones et al., Phil. Trans. R. Soc. A 2010]. If global, there are several testable mechanisms that may explain the shift including increase in burial flux of light carbon, a reduction in heavy carbon burial flux, or a large-scale circulation change perhaps associated with the transition of a major oceanic gateway. Using trace metal (B/Ca and Mg/Ca) and stable isotope (δ11B, δ18O, and δ13C) geochemistry, here we establish the nature of the peak-PCIM at sites from 3 different ocean basins (IODP Sites 690, 1209, and 1262) and begin to test several of the possible mechanisms for change. Mg/Ca in mixed-layer planktonic foraminifera show 2-3°C of sea surface warming coinciding with, and abrupt as, the benthic carbon isotope enrichment at all sites. Bottom water Δ[CO32-], as indicated by B/Ca in benthic foraminifera, abruptly increases by 30-40µmol/kgsw. While this may indicate a change in bottom water circulation, surface B-based proxies also respond with a positive shift during the peak-PCIM indicating a slight increase in surface pH and highlighting the global nature of the event.

A Novel Framework for Quantifying past Methane Recycling by Sphagnum-Methanotroph Symbiosis Using Carbon and Hydrogen Isotope Ratios of Leaf Wax Biomarkers

Science.gov (United States)

Nichols, Jonathan E.; Isles, Peter D. F.; Peteet, Dorothy M.

2014-01-01

The concentration of atmospheric methane is strongly linked to variations in Earth's climate. Currently, we can directly reconstruct the total atmospheric concentration of methane, but not individual terms of the methane cycle. Northern wetlands, dominated by Sphagnum, are an important contributor of atmospheric methane, and we seek to understand the methane cycle in these systems. We present a novel method for quantifying the proportion of carbon Sphagnum assimilates from its methanotrophic symbionts using stable isotope ratios of leaf-wax biomarkers. Carbon isotope ratios of Sphagnum compounds are determined by two competing influences, water content and the isotope ratio of source carbon. We disentangled these effects using a combined hydrogen and carbon isotope approach. We constrained Sphagnum water content using the contrast between the hydrogen isotope ratios of Sphagnum and vascular plant biomarkers. We then used Sphagnum water content to calculate the carbon isotope ratio of Sphagnum's carbon pool. Using a mass balance equation, we calculated the proportion of recycled methane contributed to the Sphagnum carbon pool, 'PRM.' We quantified PRM in peat monoliths from three microhabitats in the Mer Bleue peatland complex. Modern studies have shown that water table depth and vegetation have strong influences on the peatland methane cycle on instrumental time scales. With this new approach, delta C-13 of Sphagnum compounds are now a useful tool for investigating the relationships among hydrology, vegetation, and methanotrophy in Sphagnum peatlands over the time scales of entire peatland sediment records, vital to our understanding of the global carbon cycle through the Late Glacial and Holocene.

13C trend in an Egyptian recent tree as a record for global carbon dioxide behaviour

International Nuclear Information System (INIS)

Aly, A.I.M.; Belacy, N.; Abou El-Nour, F.

1988-01-01

The record of the 13 C content in tree rings of an Egyptian tree is used as indication for the increase of the atmospheric carbon dioxide concentration. A decrease of the 13 C isotopic content of the tree rings is observed starting from 1940 coinciding with a significant increase in the global production of CO 2 due to combustion of fossil fuel depleted in 13 C with respect to the atmosphere. Considering the local as well as the global CO 2 production rates together with the measured isotopic data, it may be concluded that the behaviour of carbon dioxide in the investigated Eastern Delta province in Egypt reflects mainly a global rather than a local effect. (author)

Stable carbon, nitrogen and sulfur isotopes in non-carbonate fractions of cold-seep carbonates

Science.gov (United States)

Feng, Dong; Peng, Yongbo; Peckmann, Jörn; Roberts, Harry; Chen, Duofu

2017-04-01

Sulfate-driven anaerobic oxidation of methane (AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. This process promotes the formation of carbonates close to the seafloor along continental margins. The geochemical characteristics of the carbonate minerals of these rocks are increasingly understood, questions remain about the geochemical characteristics of the non-carbonate fractions. Here, we report stable carbon, nitrogen and sulfur isotope patterns in non-carbonate fractions of seep carbonates. The authigenic carbonates were collected from three modern seep provinces (Black Sea, Gulf of Mexico, and South China Sea) and three ancient seep deposits (Marmorito, northern Italy, Miocene; SR4 deposit of the Lincoln Creek Formation and Whiskey Creek, western Washington, USA, Eocene to Oligocene). The δ13C values of non-carbonate fractions range from ˜-25‰ to -80‰ VPDB. These values indicate that fossil methane mixed with varying amounts of pelagic organic matter is the dominant source of carbon in these fractions. The relatively small offset between the δ34S signatures of the non-carbonate fractions and the respective sulfide minerals suggests that locally produced hydrogen sulfide is the main source of sulfur in seep environments. The δ15N values of the non-carbonate fractions are generally lower than the corresponding values of deep-sea sediments, suggesting that organic nitrogen is mostly of a local origin. This study reveals the potential of using δ13C, δ15N, δ34S values to discern seep and non-seep deposits. In cases where δ13Ccarbonate values are only moderately low due to mixing processes and lipid biomarkers have been erased in the course of burial, it is difficult to trace back AOM owing to the lack of other records. This problem is even more pronounced when authigenic carbonate is not available in ancient seep environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support

A 560 yr summer temperature reconstruction for the Western Mediterranean basin based on stable carbon isotopes from Pinus nigra ssp. laricio (Corsica/France

Directory of Open Access Journals (Sweden)

J. Kuhlemann

2012-10-01

Full Text Available The Mediterranean is considered as an area which will be affected strongly by current climate change. However, temperature records for the past centuries which can contribute to a better understanding of future climate changes are still sparse for this region. Carbon isotope chronologies from tree-rings often mirror temperature history but their application as climate proxies is difficult due to the influence of the anthropogenic change in atmospheric CO2 on the carbon isotope fractionation during photosynthetic CO2 uptake. We tested the influence of different correction models accounting for plant response to increased atmospheric CO2 on four annually resolved long-term carbon isotope records (between 400 and 800 yr derived from Corsican pine trees (Pinus nigra ssp. laricio growing at ecologically varying mountain sites on the island of Corsica. The different correction factors have only a minor influence on the main climate signals and resulting temperature reconstructions. Carbon isotope series show strong correlations with summer temperature and precipitation. A summer temperature reconstruction (1448–2007 AD reveals that the Little Ice Age was characterised by low, but not extremely low temperatures on Corsica. Temperatures have been to modern temperatures at around 1500 AD. The reconstruction reveals warm summers during 1480–1520 and 1950–2007 AD and cool summers during 1580–1620 and 1820–1890 AD.

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

Science.gov (United States)

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

2017-08-01

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

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

International Nuclear Information System (INIS)

Torquato, J.R.F.

1980-01-01

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

Climatic correlations in the stable isotope records of silver fir (Abies pindrow) trees from Kashmir, India

International Nuclear Information System (INIS)

Ramesh, R.; Bhattacharya, S.K.; Gopalan, K.

1986-01-01

A high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the Kashmir Valley has recently been reported by us. Since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site, we have compared the mean δD, δ 13 C and δ 18 O records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record. A multiple regression analysis of the two records for the period 1903-1932 yields the following: δD is most sensitive to the amount of growing season precipitation, followed by mean maximum temperature. Tree cellulose shows an amount effect analogous to precipitation samples. The temperature coefficient for δD is in good agreement with earlier estimates based on spatial correlations. δ 13 C is significantly related to humidity and cloud amount. The signs of the regression coefficients are consistent with the recent model of Francey and Farquhar for 13 C/ 12 C fractionation in C 3 plants. δ 18 O of cellulose appears to be controlled significantly by relative humidity. δ 18 O shows less overall correlation with climatic parameters than δD and δ 13 C. δD of carbon bound hydrogen and δ 18 O of tree cellulose are linearly related with a slope of 7.9±0.3, suggesting evaporative enrichment in leaf water. (orig.)

Biological fractionation of oxygen and carbon isotopes by recent benthic foraminifera

International Nuclear Information System (INIS)

Woodruff, F.; Douglas, R.G.

1980-01-01

Recent deep-sea benthic foraminifera from five East Pacific Rise box core tops have been analyzed for oxygen and carbon isotopic composition. The five equatorial stations, with water depths of between 3200 and 4600 m, yielded fourteen specific and generic taxonomic groups. Of the taxa analyzed, Uvigerina spp. most closely approaches oxygen isotopic equilibrium with ambient sea water. Pyrgo spp. was next closest to isotopic equilibrium, being on the average 0.59 per thousand depleted in 18 O relative to Uvigerina spp. Oridorsalis umbonatus also has relatively high delta 18 O values. Most other taxa were depleted in 18 O by large amounts. In no taxa was the carbon in the CaCO 3 secreted in carbon isotopic equilibrium with the dissolved HCO 3 - of ambient sea water. (Auth.)

Late Carboniferous to Late Permian carbon isotope stratigraphy

DEFF Research Database (Denmark)

Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria

2015-01-01

An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg...

Cavity Ring-down Spectroscopy for Carbon Isotope Analysis with 2 μm Diode Laser

International Nuclear Information System (INIS)

Hiromoto, K.; Tomita, H.; Watanabe, K.; Kawarabayashi, J.; Iguchi, T.

2009-01-01

We have made a prototype based on CRDS with 2 μm diode laser for carbon isotope analysis of CO 2 in air. The carbon isotope ratio was obtained to be (1.085±0.012)x10 -2 which shows good agreement with the isotope ratio measured by the magnetic sector-type mass spectrometer within uncertainty. Hence, we demonstrated the carbon isotope analysis based on CRDS with 2 μm tunable diode laser.

Linking the distribution of carbon isotope ratios in soil carbonates and speleothems to climate conditions in the past: A model for the dependence of respiration rate on soil moisture

Science.gov (United States)

Liu, Y.; Ibarra, D. E.; Winnick, M.; Caves Rugenstein, J. K.; Oster, J. L.; Druhan, J. L.

2017-12-01

The carbon isotope compositions (δ13C) of atmospheric CO2, C3-origin organic carbon, and limestone epikarst differ substantially, resulting in variable δ13C signatures recorded in secondary soil carbonates and speleothems which represent a mixture of these sources. Even though this signal has been widely used in paleoclimate studies, the extent to which carbonate δ13C is influenced by the dynamic response of organic carbon respiration rates to soil moisture variations has yet to be fully evaluated [1]. Soils that are rewetted after a prolonged drought commonly display a peak in respiration rate followed by relaxation to a lower steady state in both lab incubation experiments and field observations. This transient behavior, known as the Birch effect, has been extensively observed across a broad range of locations and soil types, and may generate more than 50% of the total respired CO2 in some ecosystems [2]. Here, we seek to identify the influence of the Birch effect on carbonate δ13C records based on a moisture-dependent modeling approach. We report compiled respiration rates of soils from the literature and fit these data as a function of soil moisture, before imposing exponential dampening with depth and applying the resulting function in a production-diffusion equation [3]. We then implement a mass balance calculation for the δ13C value of carbonate precipitated from a mixture of atmospheric and respired CO2, including mass-dependent fractionation associated with diffusive transport. Our results offer a novel prediction for depth-resolved carbonate δ13C as a function of soil moisture, and suggest that Birch effect signals may be recorded in soil carbonates and influence the magnitude of carbonate δ13C variations in speleothems. Thus, we illustrate a prediction for the range of carbonate δ13C recorded in terrestrial carbonates and suggest that differences in the range of carbonate δ13C may indicate changes in soil moisture variability, providing a new

Assessing offsets between the δ13C of sedimentary components and the global exogenic carbon pool across early Paleogene carbon cycle perturbations

NARCIS (Netherlands)

Sluijs, A.; Dickens, G.R.

2012-01-01

Negative stable carbon isotope excursions (CIEs) across the Paleocene–Eocene thermal maximum (PETM; ∼56 Ma) range between 2‰ and 7‰, even after discounting sections with truncated records. Individual carbon isotope records differ in shape and magnitude from variations in the global exogenic carbon

Evaluation of salt tolerance in wheat genotypes using growth and carbon isotopes discrimination technique

International Nuclear Information System (INIS)

Shirazi, M.U.; Khan, M.A.; Mujtaba, S.M.; Shereen, A.

2015-01-01

Studies were conducted in green house to select suitable salt tolerant wheat genotypes on the basis of growth performance and carbon isotopes discrimination (CID) technique. Nine newly developed double haploids (DH) wheat genotypes were tested under gravel culture, along with salt tolerant (LU-26s) and high yielding (Sarsabz) checks. The crop was irrigated by non-saline (control) and saline (12dS/m) water and raised up to maturity, growth parameters (i.e. plant height, plant biomass, productive tillers, spike length, number of spiklets/spike, number of grains / spike, grain weight/ spike and grain yield/ 15 plants) were recorded after harvesting. Plant samples (straw) were collected and were analyzed for carbon isotopic ratio (C12/ C13) from IAEA laboratories Vienna Austria. The data showed that there was significant decrease in all the growth parameters due to salinity. On the basis of performance in different growth parameters it was found that wheat genotypes V3-DH, V9-DH, V10-DH, V13-DH, and LU-26s had good response at 12dSm-1, thus can be categorized as better performing genotypes. Studies on carbon isotopes discrimination (CID) showed a decreasing trend under salinity. Mean CID values were 20.86 and 17.49 under two environments (non saline and saline, respectively), showing an overall 19% decrease under salinity. Generally the wheat genotypes having higher grain yield also had high carbon isotopes discrimination (CID). The relationship between grain yield and CID was positive (R2 = 0.695). The genotypes V10-DH, V13-DH with lower decrease in CID (i.e. 1.2 and 11.0%, respectively), also had high grain yield under salinity. Therefore the studies suggest that we can include CID technique as one of the selection criteria for salt tolerance. (author)

[Carbon isotope fractionation in plants]: Annual technical progress report

International Nuclear Information System (INIS)

O'Leary, M.H.

1988-01-01

Plants fractionate carbon isotopes during photosynthesis in ways which reflect photosynthetic pathway and environment. The fractionation is product of contributions from diffusion, carboxylation and other factors which can be understood using models which have been developed in our work. The object of our work is to use this fractionation to learn about the factors which control the efficiency of photosynthesis. Unlike previous studies, we do not rely principally on combustion methods, but instead develop more specific methods with substantially higher resolving power. We have recently developed a new short-term method for studying carbon isotope fractionation which promises to provide a level of detail about temperature, species, and light intensity effects on photosynthesis which has not been available until now. We are studying the isotopic compositions of metabolites (particularly aspartic acid) in C 3 plants in order to determine the role of phosphoenolpyruvate carboxylase in C 3 photosynthesis. We are studying the relative roles of diffusion and carboxylation in nocturnal CO 2 fixation in CAM plants. We are studying the use of isotopic content as an index of water-use efficiency in C 3 plants. We are developing new methods for studying carbon metabolism in plants. 3 refs

Dual temperature effects on oxygen isotopic ratio of shallow-water coral skeleton: Consequences on seasonal and interannual records

Science.gov (United States)

Juillet-Leclerc, A.; Reynaud, S.

2009-04-01

Oxygen isotopic ratio from coral skeleton is regarded for a long time as promising climate archives at seasonal scale. Although in isotopic disequilibrium relative to seawater, it is supposed to obey to the isotope thermometer. Indeed, coral oxygen isotopic records are strongly temperature dependent, but d18O-temperature calibrations derived from different corals are highly variable. The isotope thermometer assumption does not take into account vital effects due to biogenic origin of the mineral. Corals are animals living in symbiosis with algae (zooxanthellae). Interactions between symbiont photosynthesis and coral skeleton carbonation have been abundantly observed but they remain poorly understood and the effects of photosynthesis on coral growth and skeleton oxygen ratio are ignored. Coral cultured under two light conditions enabled to relate metabolic parameters and oxygen isotopic variability with photosynthetic activity. By examining responses provided by each colony they revealed that photosynthesis significantly affected d18O, by an opposite sense compared with the sole temperature influence. Since temperature and light changes are associated during seasonal variations, this complicates the interpretation of seasonal record. Additionally, this complexity is amplified because photosynthetic activity is also directly impacted by temperature variability. Thus, the annual isotopic amplitude due to the "physical" temperature influence is partly compensated through photosynthesis. Similar opposite effect is also shown by extension rate of the cultured colonies. First, we will examine and quantify consequences of photosynthesis on growth rate and oxygen isotopic signature, from cultured corals. Second, we will consider the consequences of this vital effect on data series, at seasonal and interannual time scales.

What Drives Carbon Isotope Fractionation by the Terrestrial Biosphere?

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Still, Christopher; Rastogi, Bharat

2017-11-01

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

Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

Science.gov (United States)

Ryb, U.; Eiler, J. M.

2017-12-01

The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

Stable carbon isotope fractionation of organic cyst-forming dinoflagellates: Evaluating the potential for a CO2 proxy

Science.gov (United States)

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

2015-07-01

Over the past decades, significant progress has been made regarding the quantification and mechanistic understanding of stable carbon isotope fractionation (13C fractionation) in photosynthetic unicellular organisms in response to changes in the partial pressure of atmospheric CO2 (pCO2). However, hardly any data is available for organic cyst-forming dinoflagellates while this is an ecologically important group with a unique fossil record. We performed dilute batch experiments with four harmful dinoflagellate species known for their ability to form organic cysts: Alexandrium tamarense, Scrippsiella trochoidea, Gonyaulax spinifera and Protoceratium reticulatum. Cells were grown at a range of dissolved CO2 concentrations characterizing past, modern and projected future values (∼5-50 μmol L-1), representing atmospheric pCO2 of 180, 380, 800 and 1200 μatm. In all tested species, 13C fractionation depends on CO2 with a slope of up to 0.17‰ (μmol L)-1. Even more consistent correlations were found between 13C fractionation and the combined effects of particulate organic carbon quota (POC quota; pg C cell-1) and CO2. Carbon isotope fractionation as well as its response to CO2 is species-specific. These results may be interpreted as a first step towards a proxy for past pCO2 based on carbon isotope ratios of fossil organic dinoflagellate cysts. However, additional culture experiments focusing on environmental variables other than pCO2, physiological underpinning of the recorded response, testing for possible offsets in 13C values between cells and cysts, as well as field calibration studies are required to establish a reliable proxy.

Monitoring in situ biodegradation of hydrocarbons by using stable carbon isotopes

International Nuclear Information System (INIS)

Aggarwal, P.K.; Hinchee, R.E.

1991-01-01

Spilled or leaked nonhalogenated petroleum hydrocarbons in the soil can generally be metabolized by indigenous, aerobic bacteria. In situ biological degradation of hydrocarbons may be accelerated by supplying inorganic nutrients and/or oxygen. Approaches to monitoring and verifying enhanced in situ biodegradation have included measurements of changes over time in the (a) concentration of hydrocarbons, (b) temperature, (c) number of hydrocarbon-degrading microorganisms, (d) ratio of fast-degrading hydrocarbons (e.g., pristanes or phytanes), and (e) metabolic intermediates. Measurements of oxygen consumption over time and elevated carbon dioxide concentrations in soil gas also have been used as indicators of hydrocarbon degradation. An alternative approach that may help substantiate biodegradation is to measure stable carbon isotope ratios in soil gas CO 2 . Stable carbon isotope ratio analysis is inexpensive and commercially available at many laboratories. Carbon dioxide produced by hydrocarbon degradation may be distinguished from that produced by other processes based on the carbon isotopic compositions characteristic of the source material and/or fractionation accompanying microbial metabolism. Here the authors demonstrate the applicability of the stable isotope technique for monitoring enhanced. aerobic biodegradation of hydrocarbons using data from three locations in the United States

New Carbonate Standard Reference Materials for Boron Isotope Geochemistry

Science.gov (United States)

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

2015-12-01

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

Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces

Directory of Open Access Journals (Sweden)

Shaena Montanari

2017-06-01

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

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

CERN Document Server

Franberg, Hanna; Köster, Ulli; Ammann, Markus

2008-01-01

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

Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-01

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

Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

International Nuclear Information System (INIS)

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

2015-01-01

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

Spectral isotopic methods of determining nitrogen and carbon in plant specimens with laser volatization

International Nuclear Information System (INIS)

Lazeeva, G.S.

1986-01-01

Methods have been devised for the local determination of nitrogen and carbon isotope compositions in plant specimens, which provide separate and joint determination. Local laser evaporation has been combined with spectroscopic determination of the isotope compositions in the gas phase. A continuous-wave CO 2 laser is preferable for the local evaporation; the carbon isotope composition may be determined directly on the sum of the evaporation products, whereas nitrogen must first be separated as N 2 . Methods have also been developed for the local determination of total nitrogen and carbon in a sample with isotope dilution on the basis of laser evaporation. In order to eliminate systematic errors in determining total carbon in plant material, an evaporation method free from a rim has been devised. These methods have been used in determining isotope concentration profiles in plant specimens grown in experiments employing labeled nitrogen and carbon

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

Energy Technology Data Exchange (ETDEWEB)

Liu, Yunde [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China); Laboratory of Basin Hydrology and Wetland Eco-restoration, China University of Geosciences, Wuhan 430074 (China); Zhou, Aiguo, E-mail: aiguozhou@cug.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China); Gan, Yiqun; Li, Xiaoqian [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China)

2016-05-05

Highlights: • The effect of inorganic anions on carbon isotope fractionation was evaluated. • The enrichment factors was independent concentration of NO{sub 3}{sup −}, or SO{sub 4}{sup 2−}. • Cl{sup −} significantly influenced the carbon isotope fractionation. - Abstract: Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (ε value). A comparison of ε values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the ε values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the ε values (ranging from −6.3 ± 0.8 to 10 ± 1.3‰) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate ε values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes.

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

International Nuclear Information System (INIS)

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

2016-01-01

Highlights: • The effect of inorganic anions on carbon isotope fractionation was evaluated. • The enrichment factors was independent concentration of NO_3"−, or SO_4"2"−. • Cl"− significantly influenced the carbon isotope fractionation. - Abstract: Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (ε value). A comparison of ε values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the ε values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the ε values (ranging from −6.3 ± 0.8 to 10 ± 1.3‰) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate ε values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes.

Lipid Biomarkers and Molecular Carbon Isotopes for Elucidating Carbon Cycling Pathways in Hydrothermal Vents

Science.gov (United States)

Zhang, C. L.; Dai, J.; Campbell, B.; Cary, C.; Sun, M.

2003-12-01

Increasing molecular evidence suggests that hydrothermal vents in mid-ocean ridges harbor large populations of free-living bacteria, particularly the epsilon Proteobacteria. However, pathways for carbon metabolism by these bacteria are poorly known. We are addressing this question by analyzing the lipid biomarkers and their isotope signatures in environments where the epsilon Proteobacteria are likely predominant. Solid materials were collected from hydrothermal vents in the East Pacific Rise and at the Guaymas Basin in the Gulf of California. Fatty acids extracted from these samples are dominated by 16:0 (27-41%), 18:0 (16-48%), 18:1 (11-42%), 16:1 (7-12%), and 14:0 (5-28%). In addition, 15:0 and anteiso-15:0 are significantly present (2-3%) in samples from the Guaymas Basin. The isotopic compositions of these fatty acids range from -15.0\\permil to -33.1\\permil with the most positive values occurring only in monounsaturated fatty acids (16:1 and 18:1). We are currently unable to assign these biomarkers to any of the epsilon Proteobacteria because biomarkers are poorly known for these organisms isolated from the vents. However, no polyunsaturated fatty acids were detected in these samples, which are consistent with the absence of vent animals at the sampling sites. Signature biomarkers of 20:1 and cy21:0, which are characteristic of the thermophilic chemolithoautotrophs such as Aquificales, are also absent in these samples. These results imply that the deeply branched Aquificales species do not constitute the major microbial community in these vent environments. The large range of molecular isotopic compositions suggests that these lipids are synthesized from various carbon sources with different isotopic compositions or through different biosynthetic pathways, or both. We are currently measuring the isotopic compositions of the total organic carbon in the bulk samples and will determine the fractionations between lipid biomarkers and the total organic carbon

Carbon, nitrogen and oxygen isotope fractionation during food cooking: Implications for the interpretation of the fossil human record.

Science.gov (United States)

Royer, Aurélien; Daux, Valérie; Fourel, François; Lécuyer, Christophe

2017-08-01

Stable isotope data provide insight into the reconstruction of ancient human diet. However, cooking may alter the original stable isotope compositions of food due to losses and modifications of biochemical and water components. To address this issue, carbon, nitrogen and oxygen isotope ratios were measured on meat aliquots sampled from various animals such as pork, beef, duck and chicken, and also from the flesh of fishes such as salmon, European seabass, European pilchard, sole, gilt-head bream, and tuna. For each specimen, three pieces were cooked according to the three most commonly-known cooking practices: boiling, frying and roasting on a barbecue. Our data show that cooking produced isotopic shifts up to 1.8‰, 3.5‰, and 5.2‰ for δ 13 C, δ 15 N, and δ 18 O values, respectively. Such variations between raw and cooked food are much greater than previously estimated in the literature; they are more sensitive to the type of food rather than to the cooking process itself, except in the case of boiling. Reconstructions of paleodietary may thus suffer slight bias in cases of populations with undiversified diets that are restrained toward a specific raw or cooked product, or using a specific cooking mode. In cases of oxygen isotope compositions from skeletal remains (bones, teeth), they not only constitute a valuable proxy for reconstructing past climatic conditions, but they could also be used to improve our knowledge of past human diet. © 2017 Wiley Periodicals, Inc.

Clumped Isotope Thermometry Reveals Variations in Soil Carbonate Seasonal Biases Over >4 km of Relief in the Semi-Arid Andes of Central Chile

Science.gov (United States)

Burgener, L. K.; Huntington, K. W.; Hoke, G. D.; Schauer, A. J.; Ringham, M. C.; Latorre Hidalgo, C.; Díaz, F.

2015-12-01

The application of carbonate clumped isotope thermometry to soil carbonates has the potential to shed new light on questions regarding terrestrial paleoclimate. In order to better utilize this paleoclimate tool, outstanding questions regarding seasonal biases in soil carbonate formation and the relationship between soil carbonate formation temperatures (T(Δ47)) and surface temperatures must be resolved. We address these questions by comparing C, O, and clumped isotope data from Holocene/modern soil carbonates to modern meteorological data. The data were collected along a 170 km transect with >4 km of relief in central Chile (~30°S). Previous studies have suggested that soil carbonates should record a warm season bias and form in isotopic equilibrium with soil water and soil CO2. We identify two discrete climate zones separated by the local winter snow line (~3200 m). Below this boundary, precipitation falls as rain and soil carbonate T(Δ47) values at depths >40 cm resemble summer soil temperatures; at higher elevations, precipitation falls as snow and T(Δ47) values resemble mean annual soil temperatures. Soil carbonates from the highest sample site (4700 m), which is devoid of vegetation and located near perennial snow fields, yield anomalous δ18O, δ13C, and T(Δ47) values, indicative of kinetic isotope effects that we attribute to cryogenic carbonate formation. Our results suggest that soil carbonates from depths temperature and precipitation, and should not be used as paleotemperature proxies. These findings (1) highlight the role of soil moisture in modulating soil carbonate formation and the resulting T(Δ47) values, (2) underscore the importance of understanding past soil moisture conditions when attempting to reconstruct paleotemperatures using carbonate clumped isotope thermometry, and (3) suggest that soil carbonates from high elevation or high latitude sites may form under non-equilibrium conditions.

Bicarbonate adsorption band of the chromatography for carbon isotope separation using anion exchangers

International Nuclear Information System (INIS)

Takeda, Kunihiko; Obanawa, Heiichiro; Hata, Masahisa; Sato, Katsuya

1985-01-01

The equilibria of bicarbonate ion between two phases were studied for the carbon isotope separation using anion exchangers. The condition of the formation of a bicarbonate adsorption band was quantitatively discussed. The formation of the adsorption band depends on the difference of S-potential which is the sum of the standard redection chemical potentials and L-potential which is the sum of the reduction chemical potential. The isotopic separation factor observed was about 1.012, independent of the concentrations of acid and alkali in the solutions. The isotopic separation factor was considered to be determined by the reaction of bicarbonate ion on anion exchangers and carbon dioxide dissolved in solutions. The enriched carbon isotope whose isotopic abundance ratio ( 13 C/ 12 C) was 1.258 was obtained with the column packed with anion exchangers. (author)

Carbon Isotope Chemistry in Molecular Clouds

Science.gov (United States)

Robertson, Amy N.; Willacy, Karen

2012-01-01

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

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

Science.gov (United States)

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

1985-01-01

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

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

Science.gov (United States)

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

2013-01-01

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

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

OpenAIRE

Anderson , Lucy; Dynes , Travis; Berry , Jennifer; Delaplane , Keith; McCormick , Lydia; Brosi , Berry

2014-01-01

International audience; The ability to distinguish feral and managed honeybees (Apis mellifera) has applications in studies of population genetics, parasite transmission, pollination, interspecific interactions, and bee breeding. We evaluated a diagnostic test based on theoretical differences in stable carbon isotope ratios generated by supplemental feeding. We evaluated (1) if carbon isotope ratios can distinguish feral and managed honeybees and (2) the temporal persistence of the signal aft...

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

Science.gov (United States)

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

2015-11-01

In this study, the microbial degradation of lambda-cyhalothrin in soil was investigated using compound-specific stable isotope analysis. The results revealed that lambda-cyhalothrin was biodegraded in soil under laboratory conditions. The half-lives of lambda-cyhalothrin were determined to be 49 and 161 days in non-sterile and sterile soils spiked with 2mg/kg lambda-cyhalothrin and 84 and 154 days in non-sterile and sterile soils spiked with 10mg/kg lambda-cyhalothrin, respectively. The biodegradation of lambda-cyhalothrin resulted in carbon isotope fractionation, which shifted from -29.0‰ to -26.5‰ in soil spiked with 2mg/kg lambda-cyhalothrin, and to -27.5‰ with 10mg/kg lambda-cyhalothrin. A relationship was established between the stable carbon isotope fraction and the residual concentrations of lambda-cyhalothrin by the Rayleigh equation in which the carbon isotope enrichment factor ε of the microbial degradation of lambda-cyhalothrin in the soil was calculated as -2.53‰. This study provides an approach to quantitatively evaluate the biodegradation of lambda-cyhalothrin in soil in field studies. Copyright © 2015 Elsevier B.V. All rights reserved.

Deep ocean ventilation, carbon isotopes, marine sedimentation and the deglacial CO2 rise

Directory of Open Access Journals (Sweden)

C. Heinze

2011-07-01

Full Text Available The link between the atmospheric CO2 level and the ventilation state of the deep ocean is an important building block of the key hypotheses put forth to explain glacial-interglacial CO2 fluctuations. In this study, we systematically examine the sensitivity of atmospheric CO2 and its carbon isotope composition to changes in deep ocean ventilation, the ocean carbon pumps, and sediment formation in a global 3-D ocean-sediment carbon cycle model. Our results provide support for the hypothesis that a break up of Southern Ocean stratification and invigorated deep ocean ventilation were the dominant drivers for the early deglacial CO2 rise of ~35 ppm between the Last Glacial Maximum and 14.6 ka BP. Another rise of 10 ppm until the end of the Holocene is attributed to carbonate compensation responding to the early deglacial change in ocean circulation. Our reasoning is based on a multi-proxy analysis which indicates that an acceleration of deep ocean ventilation during early deglaciation is not only consistent with recorded atmospheric CO2 but also with the reconstructed opal sedimentation peak in the Southern Ocean at around 16 ka BP, the record of atmospheric δ13CCO2, and the reconstructed changes in the Pacific CaCO3 saturation horizon.

27 CFR 24.319 - Carbon dioxide record.

Science.gov (United States)

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Carbon dioxide record. 24..., DEPARTMENT OF THE TREASURY LIQUORS WINE Records and Reports § 24.319 Carbon dioxide record. A proprietor who uses carbon dioxide in still wine shall maintain a record of the laboratory tests conducted to...

Relationships between tree height and carbon isotope discrimination

Science.gov (United States)

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

2011-01-01

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

Asymptotic giant branch stars as producers of carbon and of neutron-rich isotopes

International Nuclear Information System (INIS)

Iben, I. Jr.

1984-01-01

Carbon stars are thought to be in the asymptotic giant branch (AGB) phase of evolution, alternately burning hydrogen and helium in shells above an electron-degenerate carbon-oxygen (CO) core. The excess of carbon relative to oxygen at the surfaces of these stars is thought to be due to convective dredge-up which occurs following a thermal pulse. During a thermal pulse, carbon and neutron-rich isotopes are made in a convective helium-burning zone. In model stars of large CO core mass, the source of neutrons for producing the neutron-rich isotopes is the 22 Ne(α,n) 25 Mg reaction and the isotopes are produced in the solar system s-process distribution. In models of small core mass, the 13 C(α,n) 16 reaction is thought to be responsible for the release of neutrons, and the resultant distribution of neutron-rich isotopes is expected to vary considerably from one star to the next, with the distribution in isolated instances possibly resembling the solar system distribution of r-process isotopes

High resolution carbon isotope of Crassostrea cuttakensis: A proxy for seasonally varying carbon dynamics in a tropical delta-estuary system

Science.gov (United States)

Sreemany, Arpita

2017-04-01

The exponential increase in the atmospheric CO2 concentration and global temperature is becoming a major threat to the existence of the mankind. It has been proposed that the ˜2 ˚ C rise in the average global temperature may lead to a point of no-return where the balance between the climate and the ecosystem collapses. Therefore, detailed understanding of the major carbon reservoirs and their mutual interactions is needed for better future climate prediction. Among all the reservoirs, ocean holds ˜90 % of the exogenic carbon and promotes long term storage in sediments. However, the majority of the sedimentary carbon is of terrestrial origin and transported through rivers, which play an important role in carbon exchange between the atmosphere, terrestrial biosphere, and oceans. The transportation of organic carbon through river does not follow a simple conveyer belt model. Various organic and inorganic reactions (i.e., organic carbon degradation, inorganic carbon precipitation, primary production, community respiration) modify the state of the carbon to form a major sub-reservoir in the river, i.e., Dissolved Inorganic Carbon (DIC). So, identifying the source/s of the DIC is crucial to understand the carbon dynamics in the river. Stable carbon isotopic composition of the DIC (δ13CDIC) has long been extensively used to reveal the dominant source/s of the DIC. The majority of the large rivers, being situated in the tropical belts, show seasonal fluctuation in the DIC sources. However, seasonal sampling in the remotest reaches of these rivers hindered our thorough understanding of the seasonally varying source/s of DIC in these rivers. Many calcifying organisms precipitate their shell carbonate in equilibrium with water and hence likely to record the δ13CDICof ambient water in their shell. In this study, a living oyster (Crassostrea cuttakensis) was collected from Matla River, which is part of the Ganges Brahmaputra river delta system, and analyzed for its stable

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

Directory of Open Access Journals (Sweden)

M. E. Nowak

2017-08-01

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

Carbon isotopic changes in benthic foraminifera from the western South Atlantic: Reconstruction of glacial abyssal circulation patterns

Science.gov (United States)

Curry, W. B.; Lohmann, G. P.

1982-09-01

Oxygen- and carbon-isotopic analyses have been performed on the benthic foraminifer Planulina wuellerstorfi in seven Late Quaternary cores from the Vema Channel-Rio Grande Rise region. The cores are distributed over the water-depth interval of 2340 to 3939 m, which includes the present transition from North Atlantic Deep Water (NADW) to Antarctic Bottom Water (AABW). The carbon-isotopic records in the cores vary as a function of water depth. The shallowest and deepest cores show no significant glacial-interglacial difference in δ 13C. Four of the five cores presently located in the NADW have benthic foraminiferal δ 13C that is lower during glacial isotopic stages. Based on bathymetric gradients in δ 13C, we conclude that, like today, there were two water masses present in the Vema Channel during glacial intervals: a water mass enriched in 13C overlying another water mass depleted in 13C. The largest gradient of change of δ 13C with depth, however, occurred at 2.7 km, ˜ 1 km shallower than the present position of this gradient. On the basis of paleontologic and sedimentologic evidence, we consider it unlikely that the NADW:AABW transition shallowed to this level. Reduced carbon-isotopic gradients between the deep basins of the North Atlantic and Pacific Oceans during the last glaciation suggest that production of NADW was reduced. Lower production of NADW may have modified the local abyssal circulation pattern in the Vema Channel region.

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

Science.gov (United States)

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

2007-12-01

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

Speleothem stable isotope records for east-central Europe: resampling sedimentary proxy records to obtain evenly spaced time series with spectral guidance

Science.gov (United States)

Gábor Hatvani, István; Kern, Zoltán; Leél-Őssy, Szabolcs; Demény, Attila

2018-01-01

Uneven spacing is a common feature of sedimentary paleoclimate records, in many cases causing difficulties in the application of classical statistical and time series methods. Although special statistical tools do exist to assess unevenly spaced data directly, the transformation of such data into a temporally equidistant time series which may then be examined using commonly employed statistical tools remains, however, an unachieved goal. The present paper, therefore, introduces an approach to obtain evenly spaced time series (using cubic spline fitting) from unevenly spaced speleothem records with the application of a spectral guidance to avoid the spectral bias caused by interpolation and retain the original spectral characteristics of the data. The methodology was applied to stable carbon and oxygen isotope records derived from two stalagmites from the Baradla Cave (NE Hungary) dating back to the late 18th century. To show the benefit of the equally spaced records to climate studies, their coherence with climate parameters is explored using wavelet transform coherence and discussed. The obtained equally spaced time series are available at PANGAEA.875917" target="_blank">https://doi.org/10.1594/PANGAEA.875917.

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-09-01

The increased use of persulfate (S{sub 2}O{sub 8}{sup 2-}) for in situ chemical oxidation to treat groundwater and soils contaminated by chlorinated hydrocarbon compounds (CHCs) requires unbiased methods to assess treatment performance. Stable carbon isotope analysis offers a potential tool for assessing the in situ treatment performance of persulfate at sites contaminated with CHCs. This study investigated the extent of C isotope fractionation during oxidation of tetrachloroethene (PCE), trichloroethene (TCE) and cis-dichloroethene (cis-DCE) by persulfate activated by ferrous ion (Fe{sup 2+}). An average carbon isotope enrichment factor {epsilon}{sub bulk} of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cis-DCE were obtained in batch experiments. Variations in the initial S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratios did not result in any significant differences in carbon isotope fractionation. The occurrence of carbon isotope fractionation during oxidation and the lack of dependence of enrichment factors upon the S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratio demonstrate that carbon isotope analysis can potentially be used at contaminated sites as an additional technique to estimate treatment efficacy during oxidation of CHCs by Fe{sup 2+} activated persulfate. Highlights: Black-Right-Pointing-Pointer The performance of in situ chemical oxidation (ISCO) is still difficult to assess. Black-Right-Pointing-Pointer We investigated the potential of carbon isotope analysis as a new assessing tool. Black-Right-Pointing-Pointer C isotope of PCE, TCE and DCE oxidized by persulfate activated by Fe{sup 2+} was measured. Black-Right-Pointing-Pointer Enrichment factors of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cisDCE were obtained. Black-Right-Pointing-Pointer Carbon isotope can potentially be used to estimate the ISCO treatment efficacy.

Soil Carbon: Compositional and Isotopic Analysis

Energy Technology Data Exchange (ETDEWEB)

Moran, James J.; Alexander, M. L.; Laskin, Alexander

2016-11-01

This is a short chapter to be included in the next edition of the Encyclopedia of Soil Science. The work here describes techniques being developed at PNNL for investigating organic carbon in soils. Techniques discussed include: laser ablation isotope ratio mass spectrometry, laser ablation aerosol mass spectrometry, and nanospray desorption electrospray ionization mass spectrometry.

Organic carbon isotope ratios of recent sediments from coastal lagoons of the Gulf of Mexico, Mexico

International Nuclear Information System (INIS)

Botello, A.V.; Mandelli, E.F.; Macko, S.; Parker, P.L.

1980-01-01

The stable carbon isotope composition of sedimentary organic carbon was determined in the sediments of seven coastal lagoons of the Gulf of Mexico, Mexico. For most of the lagoons the delta 13 C values for sediments ranged from -20.1 to -23.9 parts per thousand. Anomalously low values, -26.8 to 29.3 parts per thousand were determined in sediments of two of the studied lagoons, probably due to the presence of organic carbon from anthropogenic sources, naturally absent in these environments. The delta 13 C values determined in the tissues of oysters collected at the same time in the different lagoons were very similar to those recorded in the sediments. (author)

Modeling the isotopic composition of Antarctic snow using backward trajectories: simulation of snow pit records

NARCIS (Netherlands)

Helsen, M.M.; van de Wal, R.S.W.; van den Broeke, M.R.; Masson-Delmotte, V.; Meijer, H.A.J.; Scheele, M.P.; Werner, M.

2006-01-01

The quantitative interpretation of isotope records (d18O, dD, and d excess) in ice cores can benefit from a comparison of observed meteorology with associated isotope variability. For this reason we studied four isotope records from snow pits in western Dronning Maud Land (DML), Antarctica, covering

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

Directory of Open Access Journals (Sweden)

A. Jahn

2015-08-01

Full Text Available Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM, containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14C additionally follows the 13C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem module, requiring significantly fewer computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.

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

Science.gov (United States)

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

2015-08-01

Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air-sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14C additionally follows the 13C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem module, requiring significantly fewer computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.

Boron isotope fractionation in magma via crustal carbonate dissolution.

Science.gov (United States)

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

2016-08-04

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

Boron isotope fractionation in magma via crustal carbonate dissolution

Science.gov (United States)

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

2016-08-01

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

Carbon isotope ratios in field Population II giant stars

International Nuclear Information System (INIS)

Sneden, C.; Pilachowski, C.A.; Vandenberg, D.A.; Kitt Peak National Observatory, Tucson, AZ; Victoria Univ., Canada)

1986-01-01

Carbon isotope ratios have been derived from high-resolution spectra of the CH G-band in 15 very metal-poor Population II giant stars and two similar dwarf stars. Many of the giants possess very low C-12/C-13 ratios, some approaching the CN cycle equilibrium value. The metal-poor dwarfs do not have detectable CH-13 features; thus the low carbon isotope ratios in the giants probably are due to their internal evolutions. These results strongly support the idea that at least part of the anomalously low C/N values in Population II giants arises from very efficient mixing of their envelopes into the CN cycle burning layers. Detailed calculations of the expected CNO surface abundances in Population II giants in different evolutionary states have been performed. These computations demonstrate that the observed carbon isotope ratios cannot be produced during the first dredge-up mixing phases in low-mass, low metal abundance stars. Numerical experiments show that theoretical and observational results can be brought into agreement with artificially induced extra mixing. An agent to provoke this additional mixing has not been identified with certainty yet, although internal stellar rotation is a promising candidate. 63 references

An oxygen isotope record from Lake Xiarinur in Inner Mongolia since the last deglaciation and its implication for tropical monsoon change

Science.gov (United States)

Sun, Qing; Chu, Guoqiang; Xie, Manman; Zhu, Qingzeng; Su, Youliang; Wang, Xisheng

2018-04-01

We present a high-resolution oxygen isotope record from authigenic carbonate (δ18Ocarb) from Lake Xiarinur (Inner Mongolia) since the last deglaciation. The lake is located at the modern northern limit of the monsoon, and is therefore sensitive to the extension of the East Asian summer monsoon. Based on calibration against the instrumental record, the δ18Ocar variation has been interpreted as changes in atmospheric circulation pattern on decadal time scales. On longer time scales, the δ18Ocarb in lake sediments could be mainly regulated by the relative contribution of nearby (remote) water-vapor sources associated with subtropical (tropical) monsoon through changes in the distance from sources to the site of precipitation. Increased remote water vapors from tropical monsoon would lead to lighter isotope value in our study site. Through time the δ18Ocarb record in Lake Xiarinur indicate a notable weak tropical monsoon during the Younger Dryas, a gradual increasing monsoon from the early Holocene and weakening monsoon after the middle Holocene. Oxygen isotope records from lakes and stalagmite in the Asian monsoon region across different localities show a general similar temporal pattern since the last deglaciation, and highlight a fundamental role of the tropical monsoon.

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

Science.gov (United States)

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

2015-12-01

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

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

NARCIS (Netherlands)

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

2002-01-01

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

Small-scale computerized isotope record monitoring system

Energy Technology Data Exchange (ETDEWEB)

Richards, L [Queen Elizabeth Coll., London (UK)

1979-05-01

A system in use at Queen Elizabeth College for monitoring the isotopes used by radiation workers and the precautionary medical screening of the workers is described. It consists of a PDP-11 minicomputer and flexible disk storage system. The machine is run under a single-user, real-time operating system and is linked on-line to a teleprinter and a VDU. Data is stored as a series of files, each relating to an individual worker, which can be updated individually from the VDU. The files contain information on the worker's project and medical screening records, and his holdings of isotopes and their use and disposal. A warning is printed automatically if a worker's holding exceeds the allowed maximum. The total quantity of isotopes held and their distribution in an institution such as a university can easily be monitored so that legal limits can be adhered to. The system is inexpensive and can be used by personnel not familiar with computer systems.

Monitoring of carbon isotope composition of snow cover for Tomsk region

Science.gov (United States)

Akulov, P. A.; Volkov, Y. V.; Kalashnikova, D. A.; Markelova, A. N.; Melkov, V. N.; Simonova, G. V.; Tartakovskiy, V. A.

2016-11-01

This article shows the potential of using δ13C values of pollutants in snow pack to study the human impact on the environment of Tomsk and its surroundings. We believe that it is possible to use a relation between the isotope compositions of a fuel and black carbon for establishing the origin of the latter. The main object of our investigation was dust accumulated by the snow pack in the winter of 2015-2016. The study of dust samples included the following steps: determination of the total carbon content in snow pack samples of Tomsk and its surroundings, extraction of black carbon from the dust, as well as the determination of δ13C values of the total and black carbon accumulated in the snow pack. A snow survey was carried out on the 26th of January and on the 18th of March. The relative carbon content in the dust samples was determined by using an EA Flash 2000 element analyzer. It varied from 3 to 24%. The maximum carbon content was in the dust samples from areas of cottage building with individual heating systems. The δ13C values of the total and black carbon were determined by using a DELTA V Advantage isotope mass spectrometer (TomTsKP SB RAS). The isotope composition of black carbon corresponded to that of the original fuel. This fact allowed identifying the origin of black carbon in some areas of Tomsk.

Calculation of Site-specific Carbon-isotope Fractionation in Pedogenic Oxide Minerals

Energy Technology Data Exchange (ETDEWEB)

Rustad, James R.; Zarzycki, Piotr

2008-07-29

Ab initio molecular dynamics and quantum chemistry techniques are used to calculate the structure, vibrational frequencies, and carbon-isotope fractionation factors of the carbon dioxide component [CO2(m)] of soil (oxy)hydroxide minerals goethite, diaspore, and gibbsite. We have identified two possible pathways of incorporation of CO2(m) into (oxy)hydroxide crystal structures: one in which the C4+ substitutes for four H+ [CO2(m)A] and another in which C4+ substitutes for (Al3+,Fe3+) + H+ [CO2(m)B]. Calculations of isotope fractionation factors give large differences between the two structures, with the CO2(m)A being isotopically lighter than CO2(m)B by ≈10 per mil in the case of gibbsite and nearly 20 per mil in the case of goethite. The reduced partition function ratio of CO2(m)B structure in goethite differs from CO2(g) by <1 per mil. The predicted fractionation for gibbsite is >10 per mil higher, close to those measured for calcite and aragonite. The surprisingly large difference in the carbon-isotope fractionation factor between the CO2(m)A and CO2(m)B structures within a given mineral suggests that the isotopic signatures of soil (oxy)hydroxide could be heterogeneous.

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

Science.gov (United States)

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

2016-01-01

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

Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

KAUST Repository

McMahon, Kelton; Berumen, Michael L.; Mateo, Ivan; Elsdon, Travis S.; Thorrold, Simon R.

2011-01-01

This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas. © 2011 Springer-Verlag.

Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

KAUST Repository

McMahon, Kelton

2011-08-26

This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas. © 2011 Springer-Verlag.

Distinguishing ectomycorrhizal and saprophytic fungi using carbon and nitrogen isotopic compositions

Directory of Open Access Journals (Sweden)

Weiguo Hou

2012-05-01

Full Text Available Ectomycorrhizal fungi, a group of widespread symbiotic fungi with plant, obtain carbon source from trees and improve plant mineral nutrient uptake with their widespread hyphal network. Ectomycorrhizal fungi can be used as inoculants to improve the survival rates of plantation. Saprophytic fungi use the nutrition from the debris of plant or animals, and it is difficult to distinguish the saprophytic and ectomycorrhizal fungi by morphological and anatomic methods. In this research, the differences of stable carbon and nitrogen isotopic compositions of these fungi were analyzed. The results showed that the abundances of 13C of were higher than those of ectomycorrhizal fungi and the abundances of 15N of saprophytic fungi were lower than those of ectomycorrhizal fungi. Such differences of stable carbon and nitrogen isotopic compositions between ectomycorrhizal fungi and saprophytic fungi can be ascribed to their different nutrition sources and ecological functions. These results collectively indicate that stable carbon and nitrogen isotopic compositions are an effective proxy for distinguishing between ectomycorrhizal and saprophytic fungi.

Climatic signals registered as Carbon isotopic values in Metasequoia leaf tissues: A statistical analysis

Science.gov (United States)

Yang, H.; Blais, B.; Perez, G.; Pagani, M.

2006-12-01

To examine climatic signals registered as carbon isotopic values in leaf tissues of C3 plants, we collected mature leaf tissues from sun and shade leaves of Metasequoia trees germinated from the 1947 batch of seeds from China and planted along a latitudinal gradient of the United States. Samples from 40 individual trees, along with fossilized material from the early Tertiary of the Canadian Arctic, were analyzed for C and concentration and isotopic values using EA-IRMS after the removal of free lipids. The generated datasets were then merged with climate data compiled from each tree site recorded as average values over the past thirty years (1971-2002, NOAA database). When the isotope data were cross plotted against each geographic and climatic indicator, Latitude, Mean Annual Temperature (MAT), Average Summer Mean Temperature (ASMT)(June-August), Mean Annual Precipitation (MAP), and Average Summer Mean Precipitation (ASMP) respectively correlation patterns were revealed. The best correlating trend was obtained between temperature parameters and C isotopic values, and this correlation is stronger in the northern leaf samples than the southern samples. We discovered a strong positive correlation between latitude and the offset of C isotopic values between shade and sun leaves. This investigation represents a comprehensive examination on climatic signals registered as C isotopic values on a single species that is marked by single genetic source. The results bear implications on paleoclimatic interpretations of C isotopic signals obtained from fossil plant tissues.

Duration of and decoupling between carbon isotope excursions during the end-Triassic mass extinction and Central Atlantic Magmatic Province emplacement

Science.gov (United States)

Yager, Joyce A.; West, A. Joshua; Corsetti, Frank A.; Berelson, William M.; Rollins, Nick E.; Rosas, Silvia; Bottjer, David J.

2017-09-01

Changes in δ13Ccarb and δ13Corg from marine strata occur globally in association with the end-Triassic mass extinction and the emplacement of the Central Atlantic Magmatic Province (CAMP) during the break up of Pangea. As is typical in deep time, the timing and duration of these isotopic excursions has remained elusive, hampering attempts to link carbon cycle perturbations to specific processes. Here, we report δ13Ccarb and δ13Corg from Late Triassic and Early Jurassic strata near Levanto, Peru, where intercalated dated ash beds permit temporal calibration of the carbon isotope record. Both δ13Ccarb and δ13Corg exhibit a broad positive excursion through the latest Triassic into the earliest Jurassic. The first order positive excursion in δ13Corg is interrupted by a negative shift noted in many sections around the world coincident with the extinction horizon. Our data indicate that the negative excursion lasts 85 ± 25 kyrs, longer than inferred by previous studies based on cyclostratigraphy. A 260 ± 80 kyr positive δ13Corg shift follows, during which the first Jurassic ammonites appear. The overall excursion culminates in a return to pre-perturbation carbon isotopic values over the next 1090 ± 70 kyrs. Via chronologic, isotopic, and biostratigraphic correlation to other successions, we find that δ13Ccarb and δ13Corg return to pre-perturbation values as CAMP volcanism ceases and in association with the recovery of pelagic and benthic biota. However, the initiation of the carbon isotope excursion at Levanto predates the well-dated CAMP sills from North America, indicating that CAMP may have started earlier than thought based on these exposures, or that the onset of carbon cycle perturbations was not related to CAMP.

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

Science.gov (United States)

Brookman, Tom H.; Ambrose, Stanley H.

2012-09-01

Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ13C and δ18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north-south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

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

Science.gov (United States)

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

2018-05-01

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

Foraminiferal and carbon isotope stratigraphy through the Paleocene-Eocene transition at Dee Stream, Marlborough, New Zealand

International Nuclear Information System (INIS)

Hancock, H.J.L.; Dickens, G.R.; Strong, C.P.; Hollis, C.J.; Field, B.D.

2003-01-01

Dee Stream in the Clarence River valley of New Zealand bisects a well-exposed section of marine sedimentary rocks deposited in the Early Paleogene at high southern latitudes. One hundred metres of strata lying within this section and comprising cm-dm well-bedded, siliceous limestone with marly partings was mapped, logged, and sampled to establish a detailed foraminiferal and carbon isotope stratigraphy and to examine environmental changes across the Paleocene-Eocene thermal maximum (PETM). Although low abundance and poor preservation of planktic and benthic foraminifera characterises much of the Paleocene, foraminifera and carbon isotopes clearly show that the section spans the Upper Paleocene to Lower Eocene planktic foraminiferal zones from Zone P4 to Subzone P6b, and the Subbotina triloculinoides to Pseudohastigerina wilcoxensis Zones. The δ 13 C record correlates closely to other δ 13 C curves generated from other key Early Paleogene carbonate sequences. The Dee Stream logged section contains a 1 m thick PETM interval at 26.5 m at the base of Zone P5, or the Morozovella velascoensis Subzone. Here, benthic foraminifera undergo significant extinction, Morozovella aequa makes its first appearance, and the δ 13 C of carbonate decreases by 2 permille. The benthic foraminifer Bulimina tuxpamensis dominates benthic assemblages immediately following the onset of the PETM interval, suggesting dysoxic bottom waters during this event. In conjunction with other recently examined sections from the Marlborough region, the thick and apparently continuous Paleogene record at Dee Stream provides an important site for understanding environmental change on high-latitude continental margins during the Paleogene, including the PETM. (author). 54 refs., 10 figs., 2 tabs

Carbon dioxide effects research and assessment program

International Nuclear Information System (INIS)

Jacoby, G.

1980-12-01

Information about the past and present concentrations of CO 2 in the atmosphere and variations in climate can be obtained from measurements of stable isotopes in tree rings; specifically carbon-13, oxygen-18 and deuterium. The analysis of these stable isotopes in tree rings is a relatively new and rapidly developing field. This proceedings volume contains most of the papers presented at the meeting. The first paper gives an overview of the status of carbon-13 research. Papers relating to carbon-13 are in section I and grouped separately from the contributions on carbon-14. Although the meeting was primarily concerned with stable isotopes, all carbon isotopic analysis may be helpful in understanding the carbon-13 record in tree rings. The papers on hydrogen and oxygen isotope studies are in sections II and III respectively. The remaining sections contain papers that consider more than one isotope at a time, general topics related to isotopes, atmospheric changes and tree growth, and methods of isotopic analysis

Calcification rate and the stable carbon, oxygen, and nitrogen isotopes in the skeleton, host tissue, and zooxanthellae of bleached and recovering Hawaiian corals

Science.gov (United States)

Rodrigues, Lisa J.; Grottoli, Andréa G.

2006-06-01

We tested the effectiveness of stable isotopes as recorders of physiological changes that occur during coral bleaching and recovery. Montipora capitata and Porites compressa fragments were bleached in outdoor tanks with seawater temperature raised to 30 °C (treatment corals) for one month. Additional fragments were maintained at 27 °C in separate tanks (control corals). After one month, (0 months recovery), buoyant weight was measured and a subset of fragments was frozen. Remaining fragments were returned to the reef for recovery. After 1.5, 4, and 8 months, fragments were collected, measured for buoyant weight, and frozen. Fragments were analyzed for stable carbon and oxygen isotopic compositions of the skeleton (δ 13C s; δ 18O s) and nitrogen and carbon isotopic compositions of the host tissue (δ 15N h; δ 13C h) and zooxanthellae (δ 15N z; δ 13C z). δ 13C s decreased immediately after bleaching in M. capitata, but not in P. compressa. δ 18O s of both species failed to record the warming event. During the remaining months of recovery, δ 13C s and δ 18O s were more enriched in treatment than control corals due to decreases in calcification and metabolic fractionation during that time. Increased δ 15N h of treatment P. compressa may be due to expelled zooxanthellae during bleaching and recovery. Increased δ 15N z at 1.5 months in treatment fragments of both species reflects the increased incorporation of dissolved inorganic nitrogen to facilitate mitotic cell division and/or chl a/cell recovery. Changes in δ 13C h and δ 13C z at 1.5 months in treatment M. capitata indicated a large increase in heterotrophically acquired carbon relative to photosynthetically fixed carbon. We experimentally show that isotopes in coral skeleton, host tissue and zooxanthellae can be used to verify physiological changes during bleaching and recovery, but their use as a proxy for past bleaching events in the skeletal record is limited.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-15

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

Global Carbon Cycle of the Precambrian Earth

DEFF Research Database (Denmark)

Wiewióra, Justyna

The carbon isotopic composition of distinct Archaean geological records provides information about the global carbon cycle and emergence of life on early Earth. We utilized carbon isotopic records of Greenlandic carbonatites, diamonds, graphites, marbles, metacarbonates and ultramafic rocks...... in the surface environment and recycled back into the mantle In the third manuscript we investigate the carbon cycle components, which have maintained the carbon isotope composition of the mantle constant through time. Assuming constant organic ratio of the total carbon burial (f), we show that increased.......1‰) and metacarbonate ( -6.1 ± 0.1‰ to +1.5 ± 0.0‰) rocks from the ~3.8 Ga Isua Supracrustal Belt as resulting from the Rayleigh distillation process, which affected the ultramafic reservoir with initial δ13C between -2‰ and 0‰. Due to its high primary δ13C signature, carbon in the Isuan magnesite was most likely...

High-resolution stable isotope stratigraphy of the upper Cambrian and Ordovician in the Argentine Precordillera

DEFF Research Database (Denmark)

Sial, A.N.; Peralta, S.; Gaucher, C.

2013-01-01

We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America, and the nega......We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America......, and the negative isotope carbon excursion (SNICE) has been described for the first time in South America. We report here the record of the SPICE and SNICE in a single section in the Eastern Precordillera. In the Central Precordillera, a minor middle Darriwilian positive carbon isotope excursion (MDICE) and a late...

Towards a quantitative understanding of the late Neoproterozoic carbon cycle

DEFF Research Database (Denmark)

Bjerrum, Christian Jannik; Canfield, Donald Eugene

2011-01-01

The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late...... Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features...... of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today....

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

Science.gov (United States)

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

1985-12-01

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

A STUDY ON CARBON ISOTOPE OF CO2 AND CH4 IN WESTERN DIENG PLATEU BY GAS CHROMATOGRAPHY- ISOTOPE RATIO MASS SPECTROMETER (GC-IRMS

Directory of Open Access Journals (Sweden)

Hanik Humaida

2010-06-01

Full Text Available The carbon isotope can be used to evaluate volcanism phenomenon of volcano. The study of carbon isotope of CO2 and CH4 was carried out in western Dieng Plateau by mass-spectrometer. Before analysis, sampel was separated by gas chromatography using a Porapak-Q column and a FID (Flame Ionization Detector detector. The gas was oxidized by copper oxide at 850oC before being ionized in mass-spectrometer for isotope analysis. The CO2 content in Candradimuka crater (-4.10 O/OO, indicated that the gas may be as volcanic gas. The other CO2 from Sumber and western Gua Jimat, had isotope value  of -10.05 and -12.07 O/OO, respectively, indicating contamination from crustal and subduction material. The carbon isotope of CH4 gas from Pancasan village was -63.42 O/OO, that may be categorized as biogenic gas.   Keywords: isotope, CO2, CH4, Dieng.

A biomarker stable isotope record of late Quaternary climate and organic matter export in Southwestern Taiwan

Science.gov (United States)

Chang, Q.; Hren, M. T.; Lin, A. T.; Eley, Y.; Yu, S. W.; Harris, G.

2017-12-01

We present new leaf wax n-alkane hydrogen (δD) and carbon (δ13C) isotopic data from a 36-m-long core from off-shore southwestern Taiwan to evaluate late Quaternary changes in climate and the source of organic matter exported from the landscape. The core (MD178-3291) is located on the flank of the Gaoping Submarine Canyon that connects with the Gaoping river catchment in southwestern Taiwan. The sediment deposition in this core spans the last 26 kyr, providing a unique record of glacial-interglacial changes in organic matter export from the Taiwan orogen. The δD and δ13C both show a shift in isotopic compositions at 15 kyr, that coincides with the shift in planktonic foraminifera δ18O record from the same core as well as the global sea level. We therefore interpret this dominant shift as affected by the global glacial to interglacial transition. Following by this transition and through the interglacial period, both biomarker δD and δ13C data record fluctuations that we suggest result from short timescale changes in the distribution of organic inputs to the offshore site. This change in source is most likely caused by increases in storm and landslide frequency or intensity during warmer intervals. This interpretation is supported by terrestrial records that show an increase in landslides in the Gaoping catchment and evidence for enhanced rainfall intensity and a corresponding increase in the frequency of turbidity currents.

Control strategies for laser separation of carbon isotopes

Indian Academy of Sciences (India)

Unknown

Control strategies for laser separation of carbon isotopes. V PARTHASARATHY*, A K ... The emerging market for medical applications of C-13 is projected to be in the range of hundreds of ..... thermal effects during irradiation. In the absence of ...

Multiproxy Holocene paleoclimate records from the southern Peruvian Andes - what new can we learn from the stable carbon isotope composition of high altitude organic matter deposits?

Science.gov (United States)

Skrzypek, Grzegorz; Engel, Zbyněk

2015-04-01

Interpretation of the Central Andean paleoclimate over the last millennia still represents a research challenge demanding deeper studies [1,2]. Several high-resolution paleoclimate proxies for the last 10,000 years have been developed for the northern hemisphere. However, similar proxies are very limited for South America, particularly for high altitudes where, for example, tree-ring chronologies are not available and instrumental records are very limited. Consequently, our knowledge of high altitude climate changes in arid regions of the Peruvian Andes mainly relies on ice-core and lake deposit studies. In our study, we used a new alternative proxy for interpretation of palaeoclimate conditions based on a peat core taken from the Carhuasanta Valley at the foot of Nevado Mismi in the southern Peruvian Andes (15° 30'S, 71° 43'W, 4809m a.s.l.). The stable carbon isotope composition (δ13C) of Distichia peat reflects mainly the relative variation of the mean air temperature during subsequent growing seasons [3], and allows reconstructions of palaeotemperature changes. In contrast, peat organic carbon concentration (C % wt) records mainly wetness in the valley, directly corresponding to the changes in runoff in the upper part of the catchment. The most prominent climate changes recorded in the peat over last 4ka occurred between 3040 and 2750 cal. yrs BP. The initial warming turned to a very rapid cooling to temperatures at least 2° C lower than the mean for the Late Holocene. Initially drier conditions within this event turned to a short wet phase after 2780 cal. yrs BP, when the temperature increased again. This event coincides with significant changes in peat and ice core records in the Central Andes that match the timing of the global climate event around 2.8 cal. ka BP. Climatic conditions in the study area became relatively dry and stable after the event for about 800 years. Highly variable temperatures and humidity prevailed during the last 2000 years, when

Influence of diet on the distribution of carbon isotopes in animals

International Nuclear Information System (INIS)

DeNiro, M.J.; Epstein, S.

1978-01-01

The influence of diet on the distribution of carbon isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant carbon isotopic composition. The isotopic composition of the whole body of an animal reflects the isotopic composition of its diet, but the animal is on average enriched in delta 13 C by about 1 part per thousand relative to the diet. In three of the four cases examined the 13 C enrichment of the whole body relative to the diet is balanced by a 13 C depletion of the respired CO 2 . The isotopic relationships between the whole bodies of animals and their diets are similar for different species raised on the same diet and for the same species raised on different diets. However, the delta 13 C values of whole bodies of individuals of a species raised on the same diet may differ by up to 2 parts per thousand. The relationship between the 13 C/ 12 C ratio of a tissue and the 13 C/ 12 C ratio of the diet depends both on the type of tissue and on the nature of the diet. Many of the isotopic relationships among the major biochemical fractions, namely the lipid, carbohydrate and protein fractions, are qualitatively preserved as diet carbon is incorporated into the animal. However, the difference between the delta 13 C values of a biochemical fraction in an animal and in its diet may be as large as 3 parts per thousand. The delta 13 C values of the biochemical components collagen chitin and the insoluble organic fraction of shells, all of which are often preserved in fossil material, are related to the isotopic composition of the diet. (author)

Isotopic composition of carbon of natural gases in the sedimentary basins of Kamchatka and Chukotka

Energy Technology Data Exchange (ETDEWEB)

Lobkov, V.A.; Kudriavtseva, E.I.

1981-01-01

A study was carried out on the chemical and isotopic compositions of carbon of natural gases, which are prospective for oil and gas structures. An isotopic composition of the carbon of gases, covered by wells in possible oil and gas bearing basins (Eastern Kamchatka Central Kamchatka, Western Kamchatka, Anadyrsk, and Khatyrsk), created by terrigenic rock of the cretaceous, paleogenic, and neogenic ages, with dimensions of three to six kilometers, is presented. Investigation is made of the isotopic carbon of methane, ethane, and propane in 36 gas specimens. The plan of the distribution of the tested structures is shown, and an analysis is given of the chemical and isotopic composition of carbon of the prospected areas of Kamchatka and Chukotka and the interconnection of the isotopic composition of the carbon of methane with ethane and propane. A supposition is made concerning the existence of a single equilibrious volumetric system of CH/sub 4/--C/sub 2/H/sub 6/--C/sub 3/H/sub 8/--CO/sub 2/, in which ethane and propane are by-products, and owing to this, equilibrium establish according to this more slowly. The study of the isotopic composition of carbon of methane shows, that at various areas of depth formation of hydrocarbon gases is different. A conclusion is made that the gases formed at high temperatures. This points to a significant distance in the vertical migration of gases in the given region.

Soil drying effects on the carbon isotope composition of soil respiration

Science.gov (United States)

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

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

International Nuclear Information System (INIS)

Aravena, R.; Dinel, H.

1993-01-01

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

The late Aeronian graptolite sedgwickii Event. Associated positive carbon isotope excursion and facies changes in the Prague Synform (Barrandian area, Bohemia)

Czech Academy of Sciences Publication Activity Database

Štorch, Petr; Frýda, J.

2012-01-01

Roč. 149, č. 6 (2012), s. 1089-1106 ISSN 0016-7568 R&D Projects: GA ČR GA205/09/0619 Institutional research plan: CEZ:AV0Z30130516 Keywords : carbon isotope record * community evenness * extinction * graptolites * Silurian * species richness Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.270, year: 2012

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

Science.gov (United States)

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

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

Science.gov (United States)

Hassan, Afifa Afifi

1982-01-01

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

Seasonal changes in stable carbon isotope ratios within annual growth rings of Pinus radiata

International Nuclear Information System (INIS)

Walcroft, A.; Silvester, W.; Whitehead, D.; Kelliher, F.

1997-01-01

The stable isotope composition of photosynthetically assimilated carbon (δ 13 C) is determined by the ratio of the leaf internal CO 2 concentration (c i ) to that of the ambient air (c a ), and so reflects the contribution of both stomatal conductance (g s ) and the rate of photosynthesis (A). Assimilated carbon which is subsequently laid down as wood in annual growth rings may therefore represent a time integrated record of physiological responses by the whole tree to seasonal changes in the environmental variables regulating growth. We analysed the stable carbon isotope composition of Pinus radiata wood collected from two plantation forest sites in New Zealand which differ markedly in temperature, rainfall and soil characteristics. For both sites, discs were cut from the stem of several trees near ground level and whole wood samples were taken from within individual annual growth rings over a number of years. At one site, diameter bands were installed over the 1994 - 1996 growing seasons in order to date precisely the formation of wood during that time. Trees at each site consistently showed a seasonal pattern in the stable isotope composition of wood within individual growth rings. The amplitude of seasonal δ 13 C variation at the wet and dry sites were 1-2 per thousand and 4 per thousand respectively. Mean δ 13 C values from the wet site were 3 per thousand more 13 C depleted than those from the dry site implying lower water-use efficiency (carbon assimilation per unit transpiration). A process-based, model of stomatal conductance and CO 2 assimilation was combined with a soil-water balance model to estimate the average daily leaf-level intercellular CO 2 concentration (c i ). Over two growing seasons at each site there was generally good agreement between mean canopy-level c i derived from the tree-ring δ 13 C data and modelled leaf-level c i levels. Further, the ratio of annual CO 2 assimilation to transpiration estimated by the model for each site

Foraminifera isotopic records... with special attention to high northern latitudes and the impact of sea-ice distillation processes

Energy Technology Data Exchange (ETDEWEB)

Hillaire-Marcel, Claude, E-mail: hillaire-marcel.claude@uqam.ca [GEOTOP, Universite du Quebec a Montreal, PO Box 8888, succursale ' centre ville' Montreal, Qc, H3C 3P8 (Canada)

2011-05-15

Since the reassessment of oxygen isotope paleotemperatures by N. Shackleton in the late 60s, most papers using isotopic records from planktic or benthic foraminifers imply a direct relationship between oxygen isotopes in seawater and the ice/ocean volume, thus some linkage with salinity, sea level, etc. Such assumptions are also made when incorporating 'isotopic modules' in coupled models. Here, we will further examine the linkages between salinity and oxygen isotope ratios of sea-water recorded by foraminifers, and their potential temporal and spatial variability, especially in the northern North Atlantic and the Arctic oceans. If temporal and spatial changes in the isotopic composition of precipitations and ice meltwaters tune the isotopic properties of the fresh water end-member that dilutes the ocean, rates of sea-ice formation and evaporation at the ocean surface play a further role on the salt and oxygen isotope contents of water masses. Thus, the oxygen 18-salinity relationship carries a specific isotopic signature for any given water mass. At the ocean scale, residence time and mixing of these water masses, as well as the time dependent-achievement of proxy-tracer equilibrium, will also result in variable recordings of mass transfers into the hydrosphere, notable between ice-sheets and ocean. Since these records in water mass may vary in both amplitude and time, direct correlations of isotopic records will potentially be misleading. Implications of such issues on the interpretation of oxygen isotope records from the sub-arctic seas will be discussed, as well as the inherent flaws of such records due to sedimentological and or ecological parameters.

Isotopic Hg in an Allende carbon-rich residue

Science.gov (United States)

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

1990-01-01

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

Stable carbon isotope composition of organic material and carbonate in sediment of a swamp and lakes in Honshu island, Japan

International Nuclear Information System (INIS)

Ishizuka, Toshio

1978-01-01

Recent sediments from a swamp and lakes in Honshu were analyzed for organic carbon and carbonate contents, and stable isotope ratios of carbon in the organic materials and carbonate. delta C 13 values of the carbonate tend to be distinctly larger than those of organic carbon in reducing condition as natural gas field, whereas in oxidizing SO 4 -reducing conditions, they are slightly larger than those of organic carbon within the limited range of a few per mil. Carbon isotopic compositions of organic carbon in sediment of the swamp, Obuchi-numa, were analyzed and compared with habitat analysis of associated fossil diatoms. deltaC 13 values of organic carbon in the sediment vary in correlation with the species abundance in habitat of the associated fossil diatoms, ranging from fresh-water (-0.0282) to coastal marine (-0.0236) via brackish. (auth.)

Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

Science.gov (United States)

Loader, N J; Street-Perrott, F A; Daley, T J; Hughes, P D M; Kimak, A; Levanič, T; Mallon, G; Mauquoy, D; Robertson, I; Roland, T P; van Bellen, S; Ziehmer, M M; Leuenberger, M

2015-01-06

A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (δ(13)C, δ(18)O, δ(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (δ(13)C 0.15‰, δ(18)O 0.30‰, δ(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited.

Carbon isotope analysis in apple nectar beverages

Directory of Open Access Journals (Sweden)

Ricardo Figueira

2013-03-01

Full Text Available The aims of this study were to use the isotope analysis method to quantify the carbon of C3 photosynthetic cycle in commercial apple nectars and to determine the legal limit to identify the beverages that do not conform to the safety standards established by the Brazilian Ministry of Agriculture, Livestock and Food Supply. These beverages (apple nectars were produced in the laboratory according to the Brazilian legislation. Adulterated nectars were also produced with an amount of pulp juice below the permitted threshold limit value. The δ13C values of the apple nectars and their fractions (pulp and purified sugar were measured to quantify the C3 source percentage. In order to demonstrate the existence of adulteration, the values found were compared to the limit values established by the Brazilian Law. All commercial apple nectars analyzed were within the legal limits, which enabled to identify the nectars that were in conformity with the Brazilian Law. The isotopic methodology developed proved efficient to quantify the carbon of C3 origin in commercial apple nectars.

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

NARCIS (Netherlands)

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

2013-01-01

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

Variation in stable carbon isotopes in organic matter from the Gunflint Iron Formation

International Nuclear Information System (INIS)

Barghoorn, E.S.; Knoll, A.H.; Dembicki, H. Jr.; Meinschein, W.G.

1977-01-01

In order to examine possible variations in organic carbon isotopic ratios within a single Precambrian formation, the kerogen separated from 15 samples of the approximately 2000 m.y. old Gunflint Iron Formation and the conformably overlying Rove Formation, representing a wide range of lithologies and geographic localities, was isotopically analyzed. From the resulting data, four conclusions can be drawn: (1) delta 13 C values of the shallow water algal chert facies are significantly more negative (-25 to -30 parts per thousand) than those of the deeper water chert-carbonate and taconite facies (-15 to -20 parts per thousand). Comparative data for modern marine algal mats shows a range of delta 13 C values from -8.4 to -19 parts per thousand PDB. Values obtained for fresh water mats were slightly more negative. (2) These differences in isotopic ratios can be correlated with similar differences in preserved microbiotas. (3) Anthraxolite lenses are depleted in 13 C relative to the reduced carbon in surrounding sediments. (4) The effect of Keweenawan diabase intrusions upon the carbon isotopic composition is pronounced, but limited to the immediate vicinity of the contact. (author)

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

International Nuclear Information System (INIS)

Guillon, S.; Pili, E.; Agrinier, P.

2012-01-01

CO 2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO 2 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 CO 2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of C-13 in CO 2 . Using a set of reference gases of known CO 2 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 CO 2 concentration, and 0.05 per thousand for δC-13 at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of C-13 on CO 2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO 2 concentration and 1.3 per thousand for δC-13, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO 2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source. (authors)

Interrogating trees for isotopic archives of atmospheric sulphur deposition and comparison to speleothem records

International Nuclear Information System (INIS)

Wynn, P.M.; Loader, N.J.; Fairchild, I.J.

2014-01-01

Palaeorecords which depict changes in sulphur dynamics form an invaluable resource for recording atmospheric pollution. Tree rings constitute an archive that are ubiquitously available and can be absolutely dated, providing the potential to explore local- to regional-scale trends in sulphur availability. Rapid isotopic analysis by a novel “on-line” method using elemental analyser isotope ratio mass spectrometry (EA-IRMS) is developed, achieving sample precision of <0.4‰ using sample sizes of 40 mg wood powder. Tree cores from NE Italy show trends in pollution, evidenced through increasing concentrations of sulphur towards the youngest growth, and inverse trends in sulphur isotopes differentiating modern growth with light sulphur isotopes (+0.7‰) from pre-industrial growth (+7.5‰) influenced by bedrock composition. Comparison with speleothem records from the same location demonstrate replication, albeit offset in isotopic value due to groundwater storage. Using EA-IRMS, tree ring archives form a valuable resource for understanding local- to regional-scale sulphur pollution dynamics. - Highlights: • Sulphur isotopes from tree rings are analysed using ‘on-line’ EA combustion. • Isotopes differentiate modern growth influenced by pollution from pre-industrial growth. • Biogeochemical cycling imparts minimal delay in sulphur incorporation into tree rings. • Trends in pollution are replicated between speleothems and trees from the same location. - Sulphur isotopes extracted from tree ring records are used to identify twentieth century pollution dynamics at the local- to regional-scale

Disentangling Diagenesis From the Rock Record: An Example From the Permo-Triassic Wordie Creek Formation, East Greenland

Science.gov (United States)

Roberts, J.; Turchyn, A. V.; Wignall, P. B.; Newton, R. J.; Vane, C. H.

2018-01-01

The measurement of isotope ratios in sedimentary rocks deposited over geological time can provide key insights to past environmental change over important intervals in the past. However, it is important to be aware that secondary alteration can overprint the original isotopic records. We demonstrate this principle using high-resolution carbon, sulfur, and oxygen isotope measurements in organic carbon, pyrite, and carbonate minerals (δ13Corg, δ34Spyr, δ34SCAS, δ13Ccarb, and δ18Ocarb) and kerogen analyses (HI and OI) from the Wordie Creek Formation, East Greenland. These sediments were initially deposited across the Permo-Triassic transition, but as we will show, the carbonate record has been altered by interaction with meteoric water significantly after initial deposition. Comparison of the better preserved organic carbon and pyrite records with a proximal Permo-Triassic sequence reveals significant pyrite-sulfur isotope variability across the Permo-Triassic transition. This regional heterogeneity argues against basin-wide euxinia and instead suggests localized changes in sulfur fractionation in response to variations in organic carbon flux. This hypothesis can be used to explain seemingly inconsistent regional trends in other sulfur isotopes across the Permo-Triassic transition.

Isotopic fractionation between organic carbon and carbonate carbon in Precambrian banded ironstone series from Brazil

International Nuclear Information System (INIS)

Schidlowski, M.; Eichmann, R.; Fiebiger, W.

1976-01-01

37 delta 13 Csub(org) and 9 delta 13 Csub(carb) values furnished by argillaceous and carbonate sediments from the Rio das Velhas and Minas Series (Minas Gerais, Brazil) have yielded means of -24.3 +- 3.9 promille [PDB] and -0.9 +- 1.4 promille [PDB], respectively. These results, obtained from a major sedimentary banded ironstone province with an age between 2 and 3 x 10 9 yr, support previous assumptions that isotopic fractionation between inorganic and organic carbon in Precambrian sediments is about the same as in Phanerozoic rocks. This is consistent with a theoretically expected constancy of the kinetic fractionation factor governing biological carbon fixation and, likewise, with a photosynthetic pedigree of the reduced carbon fraction of Precambrian rocks. (orig.) [de

Carbon isotopic composition of fossil leaves from the Early ...

Indian Academy of Sciences (India)

considerable variation in carbon isotopic composition. The Trambau ... One of the most significant changes in the ocean atmosphere .... cryogenic separation of water, CO2 was dynami- .... light condition, nutrients and temperature are low,.

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

Science.gov (United States)

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

2003-12-01

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

Stable carbon isotope biogeochemistry of lakes along a trophic gradient

NARCIS (Netherlands)

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

2014-01-01

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

Stable and radioactive carbon in Indian soils: implications to soil carbon dynamics

International Nuclear Information System (INIS)

Laskar, A.H.; Yadava, M.G.; Ramesh, R.

2011-01-01

Radiocarbon is a very useful tool to study soil carbon dynamic. The mean residence time of SOC in Indian soils is about a century at the top 0-15 cm, increases linearly to reach values ranging from 2000 to 4000 yrs at a depth of 100 cm. It mainly depends on the clay content indicating that the clay is the main governing factor for SOC stabilization. Stable carbon and oxygen isotopes in soil carbonates and SOC are good proxies for paleoclimate and paleovegetation reconstruction. The present day sub-humid climate in the lower Narmada valley has been established prior to ∼ 3 ka. Two comparatively arid phases around 2.1 and 1.3 ka are recorded by oxygen isotopes of soil carbonates; consistent with other proxy records showing its regional significance

A small-scale computerized isotope record monitoring system

International Nuclear Information System (INIS)

Richards, L.

1979-01-01

A system in use at Queen Elizabeth College for monitoring the isotopes used by radiation workers and the precautionary medical screening of the workers is described. It consists of a PDP-11 minicomputer and flexible disk storage system. The machine is run under a single-user, real-time operating system and is linked on-line to a teleprinter and a VDU. Data is stored as a series of files, each relating to an individual worker, which can be updated individually from the VDU. The files contain information on the worker's project and medical screening records, and his holdings of isotopes and their use and disposal. A warning is printed automatically if a worker's holding exceeds the allowed maximum. The total quantity of isotopes held and their distribution in an institution such as a university can easily be monitored so that legal limits can be adhered to. The system is inexpensive and can be used by personnel not familiar with computer systems. (author)

C isotope fractionation during heterotrophic activity driven carbonate precipitation

Science.gov (United States)

Balci, Nurgul; Demirel, Cansu

2016-04-01

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

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

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-01-01

The substantial increase in atmospheric greenhouse gas concentrations and their role in global warming have become major concerns of world governments. Application of isotope techniques to label sources and sinks of CO{sub 2} and other greenhouse gases has emerged as a potentially powerful method for reducing uncertainties in the global CO{sub 2} budgets and for tracing pathways and interaction of terrestrial, oceanic, and atmospheric pools of carbon. As with CO{sub 2} concentration measurements, meaningful integration of isotopes in global models requires careful attention to quality assurance, quality control and inter-comparability of measurements made by a number of networks and laboratories. To support improvements in isotope measurement capabilities, the IAEA began implementing Co-ordinated Research Projects (CRPs) in 1992. The first project, entitled Isotope Variations of Carbon Dioxide and other Trace Gases in the Atmosphere, was implemented from 1992 to 1994. A significant contribution was made towards a better understanding of the global carbon cycle and especially of the sources and sinks of carbon with data on the {sup 14}C and {sup 13}C content of atmospheric CO{sub 2}, pointing to a better understanding of the problem of the 'missing sink' in the global carbon cycle. Important methodological developments in the field of high precision stable isotope mass spectrometry and improved data acquisition procedures emerged from work carried out within the framework of this programme. The development of pressurized gas standards and planning for an associated interlaboratory calibration were initiated. Due to the good progress and long standing nature of the required work a second CRP was initiated and implemented from 1996 to 1999. It was entitled Isotope aided Studies of Atmospheric Carbon Dioxide and Other Trace Gases - Phase II, to document the close relationship of both programmes. This publication provides an overview of the scientific outcomes of the

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

International Nuclear Information System (INIS)

2002-01-01

The substantial increase in atmospheric greenhouse gas concentrations and their role in global warming have become major concerns of world governments. Application of isotope techniques to label sources and sinks of CO 2 and other greenhouse gases has emerged as a potentially powerful method for reducing uncertainties in the global CO 2 budgets and for tracing pathways and interaction of terrestrial, oceanic, and atmospheric pools of carbon. As with CO 2 concentration measurements, meaningful integration of isotopes in global models requires careful attention to quality assurance, quality control and inter-comparability of measurements made by a number of networks and laboratories. To support improvements in isotope measurement capabilities, the IAEA began implementing Co-ordinated Research Projects (CRPs) in 1992. The first project, entitled Isotope Variations of Carbon Dioxide and other Trace Gases in the Atmosphere, was implemented from 1992 to 1994. A significant contribution was made towards a better understanding of the global carbon cycle and especially of the sources and sinks of carbon with data on the 14 C and 13 C content of atmospheric CO 2 , pointing to a better understanding of the problem of the 'missing sink' in the global carbon cycle. Important methodological developments in the field of high precision stable isotope mass spectrometry and improved data acquisition procedures emerged from work carried out within the framework of this programme. The development of pressurized gas standards and planning for an associated interlaboratory calibration were initiated. Due to the good progress and long standing nature of the required work a second CRP was initiated and implemented from 1996 to 1999. It was entitled Isotope aided Studies of Atmospheric Carbon Dioxide and Other Trace Gases - Phase II, to document the close relationship of both programmes. This publication provides an overview of the scientific outcomes of the studies conducted within Phase

Morphology, molecular structure, and stable carbon isotopic composition of black carbon (BC) in urban topsoils.

Science.gov (United States)

Zong, Yutong; Xiao, Qing; Lu, Shenggao

2018-02-01

Urban soils contain significant amounts of black carbon (BC) from biomass and fossil fuel combustion and regard to be a pool of BC. BC in urban soils has multiple effects on environmental processes in urban system, such as global climate change, air quality, and public health. Urban topsoil samples (0-10 cm) were collected from Anshan, Liaoning Province, northeast China, which is one of the most important old steel industrial bases in China. The BC in urban topsoils was extracted using the density method. Their chemical composition, morphology, molecular structure, and stable carbon isotopic composition were examined using elemental analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and stable carbon isotope (δ 13 C). Elemental analysis shows that carbon content in the BC of studied soils ranged from 64.5 to 78.4%, with the average more than 70%. The O/C atomic ratio of BC is on average 0.18. The BC particle displays different morphology, including porous spherical, irregular porous fragmentary, and blocky shapes. The porous spherical BC particles has atomic molar O/C ratio determined by SEM-EDS ranging from 0.04 to 0.37. XRD indicates that BC exists in mainly combining with mineral phases hematite (Fe 2 O 3 ), kaolinite (Al 2 Si 2 O 5 (OH) 4 ), quartz (SiO 2 ), and calcite (CaCO 3 ). The FTIR spectra of BC particles show major bands at approximately 3400 cm -1 (O-H), 2920 cm -1 (C = H), 1600 cm -1 (C = C), 1230 cm -1 (C = O), and 1070 cm -1 (C = O). The stable carbon isotope (δ 13 C) of BC ranges from -24.48 to -23.18‰ with the average of -23.79 ± 0.39‰. The concentration of BC in the industrial area is significantly (p fuel combustion. Results indicated that a combination of atomic O/C ratio, porous structure, and stable carbon isotopic (δ 13 C) of BC could reflect effectively the origin of BC

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

Science.gov (United States)

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

2017-03-01

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

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

Science.gov (United States)

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

2014-01-01

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

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Science.gov (United States)

de Winter, Niels J; Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Isotopic chemical weathering behaviour of Pb derived from a high-Alpine Holocene lake-sediment record

Science.gov (United States)

Gutjahr, Marcus; Süfke, Finn; Gilli, Adrian; Anselmetti, Flavio; Glur, Lukas; Eisenhauer, Anton

2017-04-01

Several studies assessing the chemical weathering systematics of Pb isotopes provided evidence for the incongruent release of Pb from source rocks during early stages of chemical weathering, resulting in runoff compositions more radiogenic (higher) than the bulk source-rock composition [e.g. 1]. Deep NW Atlantic seawater Pb isotope records covering the last glacial-interglacial transition further support these findings. Clear excursions towards highly radiogenic Pb isotopic input in the deep NW Atlantic seen during the early Holocene, hence after the large-scale retreat of the Laurentide Ice Sheet in North America, are interpreted to be controlled by preferential release of radiogenic Pb from U- and Th-rich mineral phases during early stages of chemical weathering that are less resistant to chemical dissolution than other rock-forming mineral phases [2-4]. To date, however, no terrestrial Pb isotope record exists that could corroborate the evidence from deep marine sites for efficient late deglacial weathering and washout of radiogenic Pb. We present a high-resolution adsorbed Pb isotope record from a sediment core retrieved from Alpine Lake Grimsel (1908 m.a.s.l.) in Switzerland, consisting of 117 Pb compositions over the past 10 kyr. This high-Alpine study area is ideally located for incipient and prolonged chemical weathering studies. The method used to extract the adsorbed lake Pb isotope signal is identical to previous marine approaches targeting the authigenic Fe-Mn oxyhydroxides fraction within the lake sediments [5, 6]. The Pb isotope compositions are further accompanied by various elemental ratios derived from the same samples that equally trace climatic boundary conditions in the Grimsel Lake area. The Pb isotopic composition recorded in Lake Grimsel is remarkably constant throughout the majority of the Holocene until ˜2.5 ka BP, despite variable sediment composition and -age, and isotopically relatively close to the signature of the granitic source rock

Normalization of stable isotope data for carbonate minerals: implementation of IUPAC guideline

Science.gov (United States)

Kim, Sang-Tae; Coplen, Tyler B.; Horita, Juske

2015-01-01

Carbonate minerals provide a rich source of geochemical information because their δ13C and δ18O values provide information about surface and subsurface Earth processes. However, a significant problem is that the same δ18O value is not reported for the identical carbonate sample when analyzed in different isotope laboratories in spite of the fact that the International Union of Pure and Applied Chemistry (IUPAC) has provided reporting guidelines for two decades. This issue arises because (1) the δ18O measurements are performed on CO2 evolved by reaction of carbonates with phosphoric acid, (2) the acid-liberated CO2 is isotopically fractionated (enriched in 18O) because it contains only two-thirds of the oxygen from the solid carbonate, (3) this oxygen isotopic fractionation factor is a function of mineralogy, temperature, concentration of the phosphoric acid, and δ18O value of water in the phosphoric acid, (4) researchers may use any one of an assortment of oxygen isotopic fractionation factors that have been published for various minerals at various reaction temperatures, and (5) it sometimes is not clear how one should calculate δ18OVPDB values on a scale normalized such that the δ18O value of SLAP reference water is −55.5 ‰ relative to VSMOW reference water.

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

Directory of Open Access Journals (Sweden)

Dorota Porowska

2015-10-01

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

Application of carbon isotope analyses in food technology

International Nuclear Information System (INIS)

Szanto, Zsuzsa; Svingor, E.; Futo, I.; Palcsu, L.; Molnar, M.

2001-01-01

The vast economic size of the food market offers great temptations for the production and sale of fraudulent products, adulterated products and synthetic products that are labeled as natural ones. Conventional techniques of chemical analyses have served the food industry well for many years but are limited in their ability to detect certain types of fraudulent or mislabelled products. The aversion to added sugar and the demand for 'all natural' food products among consumers has led to a great deal of mislabelling on the part of food processors in order to achieve greater economic gain. The nature of deceptions detectable by carbon Stable Isotope Ratio Analysis (SIRA) in food technology falls into three broad categories. The most common is the adulteration of an expensive natural product, such as apple juice, with a much cheaper natural product such as cane sugar or high fructose corn syrup (HFCS). The second is outright falsification of a food. An example is maple syrup produced by simple addition of maple flavoring to a sugar syrup or HFCS. The third general category is the sale of synthetic materials as natural ones or the addition of synthetic materials to natural ones in order to increase the volume of the product. The procedure for using carbon SIRA in monitoring food products involves two stages. It must first be established that the product to be analyzed, or some specific component of it, has a particular isotopic composition that can be distinguished from that of the materials that might be used to adulterate it. Potential adulterating components are then analyzed to establish their isotopic identity. The carbon SIRA method cannot, in general, be used to establish purity unequivocally but it can be used to establish impurity or adulteration with a high degree of success. The overall process of carbon SIRA consists of three stages: selection of the sample or the isolation of the particular compound to be analyzed, conversion of this compound into CO 2 gas

Theoretical isotopic fractionation between structural boron in carbonates and aqueous boric acid and borate ion

Science.gov (United States)

Balan, Etienne; Noireaux, Johanna; Mavromatis, Vasileios; Saldi, Giuseppe D.; Montouillout, Valérie; Blanchard, Marc; Pietrucci, Fabio; Gervais, Christel; Rustad, James R.; Schott, Jacques; Gaillardet, Jérôme

2018-02-01

The 11B/10B ratio in calcite and aragonite is an important proxy of oceanic water pH. However, the physico-chemical mechanisms underpinning this approach are still poorly known. In the present study, we theoretically determine the equilibrium isotopic fractionation properties of structural boron species in calcium carbonates, BO33-, BO2(OH)2- and B(OH)4- anions substituted for carbonate groups, as well as those of B(OH)4- and B(OH)3 species in vacuum. Significant variability of equilibrium isotopic fractionation properties is observed among these structural species which is related to their contrasted coordination state, Bsbnd O bond lengths and atomic-scale environment. The isotopic composition of structural boron does not only depend on its coordination number but also on its medium range environment, i.e. farther than its first coordination shell. The isotopic fractionation between aqueous species and their counterparts in vacuum are assessed using previous investigations based on similar quantum-mechanical modeling approaches. At 300 K, the equilibrium isotope composition of structural trigonal species is 7-15‰ lighter than that of aqueous boric acid molecules, whereas substituted tetrahedral borate ions are heavier than their aqueous counterparts by 10-13‰. Although significant uncertainties are known to affect the theoretical prediction of fractionation factors between solids and solutions, the usually assumed lack of isotopic fractionation during borate incorporation in carbonates is challenged by these theoretical results. The present theoretical equilibrium fractionation factors between structural boron and aqueous species differ from those inferred from experiments which may indicate that isotopic equilibrium, unlike chemical equilibrium, was not reached in most experiments. Further research into the isotopic fractionation processes at the interface between calcium carbonates and aqueous solution as well as long duration experiments aimed at

Separation of polybrominated diphenyl ethers in fish for compound-specific stable carbon isotope analysis

Energy Technology Data Exchange (ETDEWEB)

Zeng, Yan-Hong [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate University of Chinese Academy of Sciences, Beijing, 100049 (China); Luo, Xiao-Jun, E-mail: luoxiaoj@gig.ac.cn [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Chen, Hua-Shan; Wu, Jiang-Ping; Chen, She-Jun; Mai, Bi-Xian [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China)

2012-05-15

A separation and isotopic analysis method was developed to accurately measure the stable carbon isotope ratios of polybrominated diphenyl ethers (PBDEs) with three to six substituted bromine atoms in fish samples. Sample extracts were treated with concentrated sulfuric acid to remove lipids, purified using complex silica gel column chromatography, and finally processed using alumina/silica (Al/Si) gel column chromatography. The purities of extracts were verified by gas chromatography and mass spectrometry (GC-MS) in the full-scan mode. The average recoveries of all compounds across the purification method were between 60% and 110%, with the exception of BDE-154. The stable carbon isotopic compositions of PBDEs can be measured with a standard deviation of less than 0.5 Per-Mille-Sign . No significant isotopic fraction was found during the purification of the main PBDE congeners. A significant change in the stable carbon isotope ratio of BDE-47 was observed in fish carcasses compared to the original isotopic signatures, implying that PBDE stable carbon isotopic compositions can be used to trace the biotransformation of PBDEs in biota. - Highlights: Black-Right-Pointing-Pointer A method for the purification of PBDEs for CSIA was developed. Black-Right-Pointing-Pointer The {delta}{sup 13}C of PBDE congeners can be measured with a standard deviation of less than 0.5 Per-Mille-Sign . Black-Right-Pointing-Pointer Common carp were exposed to a PBDE mixture to investigate debromination. Black-Right-Pointing-Pointer Ratios of the {delta}{sup 13}C values can be used to trace the debromination of PBDE in fish.

Measurement of organic carbon stable isotope composition of different soil types by EA-IRMS system

International Nuclear Information System (INIS)

Qi Biao; Ding Lingling; Cui Jiehua; Wang Yanhong

2009-01-01

Element analyzer-isotope ratio mass spectrometers (EA-IRMS) is a rapid and precise method for measuring stable carbon isotope. Pure CO 2 reference gas was calibrated via international standard-Urea, and the δ 13 C us PDB value of pure CO 2 is (-29.523 ± 0.0181)%. Stability and linearity of the EA-IRMS system, precision of δ 13 C measurement for samples were tested through experimental comparison. Moreover, determination method of organic carbon stable isotope in soil was based on the system. The EA-IRMS system had well linearity when ion intensity ranged from 1.0 to 7.0V, and it excelled the total linearity when the ion intensity was from 1.5 to 5.0V, and the accurate result of δ 13 C for sample analysis could be obtained with precision of 0.015%. If carbon content in sample is more than 5μg, the requirement for analyzing accurate result of δ 13 C could be achieved. The organic carbon stable isotope was measured in 18 different types soil samples, the average natural abundance of 13 C was 1.082%, and the organic carbon stable isotope composition was significantly different among different type soils. (authors)

Carbonate stable isotope constraints on sources of arsenic contamination in Neogene tufas and travertines of Attica, Greece

Science.gov (United States)

Kampouroglou, Evdokia E.; Tsikos, Harilaos; Economou-Eliopoulos, Maria

2017-11-01

We presented new C and O isotope data of rockforming calcite in terrestrial carbonate deposits from Neogene basins of Attica (Greece), coupled with standard mineralogical and bulk geochemical results. Whereas both isotope datasets [δ18O from -8.99 to -3.20‰(VPDB); δ13C from -8.17 to +1.40‰(VPDB)] could be interpreted in principle as indicative of a meteoric origin, the clear lack of a statistical correlation between them suggests diverse sources for the isotopic variation of the two elements. On the basis of broad correlations between lower carbon isotope data with increasing Fe and bulk organic carbon, we interpreted the light carbon isotope signatures and As enrichments as both derived mainly from a depositional process involving increased supply of metals and organic carbon to the original basins. Periodically augmented biological production and aerobic cycling of organic matter in the ambient lake waters, would have led to the precipitation of isotopically light calcite in concert with elevated fluxes of As-bearing iron oxy-hydroxide and organic matter to the initial terrestrial carbonate sediment. The terrestrial carbonate deposits of Attica therefore represented effective secondary storage reservoirs of elevated As from the adjacent mineralized hinterland; hence these and similar deposits in the region ought to be regarded as key geological candidates for anomalous supply of As to local soils, groundwater and related human activities.

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

Directory of Open Access Journals (Sweden)

N. Brüggemann

2011-11-01

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

Effects of Water Vapor on the Data Quality of the Stable Oxygen Isotopic Ratio of Atmospheric Carbon Dioxide

Science.gov (United States)

Evans, C. U.; White, J. W.; Vaughn, B.; Tans, P. P.; Pardo, L.

2007-12-01

specific humidity, below which air flask samples can be trusted. This approach may allow segregation of suspect and trusted data, and thus provide an improved record of oxygen isotopic ratios of carbon dioxide over the past two decades.

A reconstruction of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the last glacial inception

Directory of Open Access Journals (Sweden)

R. Schneider

2013-11-01

δ13Catm level in the Penultimate (~ 140 000 yr BP and Last Glacial Maximum (~ 22 000 yr BP, which can be explained by either (i changes in the isotopic composition or (ii intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS5.5 (120 000 yr BP. Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

Descriptions of carbon isotopes within the energy density functional theory

International Nuclear Information System (INIS)

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

2014-01-01

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

Online stable carbon isotope ratio measurement in formic acid, acetic acid, methanol and ethanol in water by high performance liquid chromatography-isotope ratio mass spectrometry

International Nuclear Information System (INIS)

Tagami, Keiko; Uchida, Shigeo

2008-01-01

A suitable analysis condition was determined for high performance liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS) while making sequential measurements of stable carbon isotope ratios of δ 13 C in formic acid, acetic acid, methanol and ethanol dissolved in water. For this online column separation method, organic reagents are not applicable due to carbon contamination; thus, water and KH 2 PO 4 at low concentrations were tested as mobile phase in combination with a HyPURITY AQUASTAR TM column. Formic acid, acetic acid, methanol and ethanol were separated when 2 mM KH 2 PO 4 aqueous solution was used. Under the determined analysis condition for HPLC-IRMS, carbon concentrations could be measured quantitatively as well as carbon isotope ratio when carbon concentration was higher than 0.4 mM L for each chemical

Carbon isotopic fractionation in live benthic foraminifera -comparison with inorganic precipitate studies

Energy Technology Data Exchange (ETDEWEB)

Grossmann, E L [University of Southern California, Los Angeles (USA). Dept. of Geological Sciences

1984-07-01

Carbon and oxygen isotopic analyses have been performed on live-stained aragonitic and calcitic benthic foraminifera and dissolved inorganic carbon from the Southern California Borderland to examine carbon isotopic fractionation in foraminifera. Temperature, salinity and pH data have also been collected to permit accurate determination of the delta/sup 13/C of bicarbonate ion and thus aragonite-HCO/sub 3//sup -/ and calcite-HCO/sub 3//sup -/ isotopic enrichment factors (epsilonsub(ar-b) and epsilonsub(cl-b), respectively). Only species which precipitate in /sup 18/O equilibrium have been considered. epsilonsub (ar-b) values based on Hoeglundina elegans range from 1.9 per mille at 2.7 deg C to 1.1 per mille at 9.5 deg C. The temperature dependence of epsilonsub(ar-b) is considerably greater than the equilibrium equation would predict and may be due to a vital effect. The calcitic foraminifera Cassidulina tortuosa, Cassidulina braziliensis, and Cassidulina limbata, Bank and Terrace dwellers, have s

Nitrogen isotopes in bulk marine sediment: linking seafloor observations with subseafloor records

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J.-E. Tesdal

2013-01-01

Full Text Available The stable isotopes of nitrogen offer a unique perspective on changes in the nitrogen cycle, past and present. However, the presence of multiple forms of nitrogen in marine sediments can complicate the interpretation of bulk nitrogen isotope measurements. Although the large-scale global patterns of seafloor δ¹⁵N have been shown to match process-based expectations, small-scale heterogeneity on the seafloor, or alterations of isotopic signals during translation into the subseafloor record, could obscure the primary signals. Here, a public database of nitrogen isotope measurements is described, including both seafloor and subseafloor sediment samples ranging in age from modern to the Pliocene, and used to assess these uncertainties. In general, good agreement is observed between neighbouring seafloor sites within a 100 km radius, with 85% showing differences of < 1‰. There is also a good correlation between the δ¹⁵N of the shallowest (< 5 ka subseafloor sediments and neighbouring seafloor sites within a 100 km radius (R² = 0.83, which suggests a reliable translation of sediments into the buried sediment record. Meanwhile, gradual δ¹⁵N decreases over multiple glacial–interglacial cycles appear to reflect post-depositional alteration in records from the deep sea (below 2000 m. We suggest a simple conceptual model to explain these 100-kyr-timescale changes in well-oxygenated, slowly accumulating sediments, which calls on differential loss rates for pools of organic N with different δ¹⁵N. We conclude that bulk sedimentary nitrogen isotope records are reliable monitors of past changes in the marine nitrogen cycle at most locations, and could be further improved with a better understanding of systematic post-depositional alteration. Furthermore, geochemical or environmental criteria should be developed in order to effectively identify problematic locations and to account for

Isotopic Hg in an Allende carbon-rich residue

International Nuclear Information System (INIS)

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

1990-01-01

A carbon-rich residue from Allende subjected to stepwise heating yielded two isotopically resolvable types of Hg: one with an (Hg-196)/(Hg-202) concentration ratio the same as terrestrial (monitor) Hg; the other enriched in Hg-196 relative to Hg-202 by about 60 percent. Hg with the 202 isotope enriched relative to 196, as is found in bulk Allende, was not observed. Whether the result of mass fractionation or nucleosynthesis, the distinct types of Hg entered different carrier phases and were not thermally mobilized since the accretion of the Allende parent body. 9 refs

Carbon and oxygen isotope time series records of planktonic and benthic foraminifera from the Arabian Sea: Implications on upwelling processes

Digital Repository Service at National Institute of Oceanography (India)

Naidu, P.D.; Niitsuma, N.

changes associated with the calci¢cation depth of these twospecies. Ingeneral, Globigerina bulloides exhibitsgreater N 18 O amplitude £uctuations compared to Pulle- niatina obliquiloculata and Uvigerina excellens (Fig.3).TherangeofN 18 Ochangesin...,thelocalbottomwatertem- perature changes associated with monsoon circu- lationwouldaccountforthe0.4xhighershiftin N 18 Onoticed atODPSite723. 4.3. Carbon isotopes The N 13 Cvaluesof Globigerina bulloides, Pulle- niatina obliquiloculata and Uvigerina excellens vary from 31.13 to 32...

Stalagmite carbon isotopes and dead carbon proportion (DCP) in a near-closed-system situation: An interplay between sulphuric and carbonic acid dissolution

Science.gov (United States)

Bajo, Petra; Borsato, Andrea; Drysdale, Russell; Hua, Quan; Frisia, Silvia; Zanchetta, Giovanni; Hellstrom, John; Woodhead, Jon

2017-08-01

In this study, the 'dead carbon proportion' (DCP) calculated from combined U-Th and radiocarbon analyses was used to explore the carbon isotope systematics in Corchia Cave (Italy) speleothems, using the example of stalagmite CC26 which grew during the last ∼12 ka. The DCP values in CC26 are among the highest ever recorded in a stalagmite, spanning the range 44.8-68.8%. A combination of almost closed-system conditions and sulphuric acid dissolution (SAD) are proposed as major drivers in producing such a high DCP with minor contribution from old organic matter from the deep vadose zone. The long-term decrease in both DCP and δ13C most likely reflects post-glacial soil recovery above the cave, with a progressive increase of soil CO2 contribution to the total dissolved inorganic carbon (DIC). Pronounced millennial-scale shifts in DCP and relatively small coeval but antipathetic changes in δ13C are modulated by the effects of hydrological variability on open and closed-system dissolution, SAD and prior calcite precipitation. Hence, the DCP in Corchia Cave speleothems represents an additional proxy for rainfall amount.

Patterns in Stable Isotope Values of Nitrogen and Carbon in ...

Science.gov (United States)

Stable isotope measurements of nitrogen and carbon (15N, 13ddC) are often used to characterize estuarine, nearshore, and open ocean ecosystems. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, the continental shelf is less studied. To address this, and as a first step toward developing a surrogate for base-level isotopic signature in this region, we collected surface and deep water samples from the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras, periodically between 2000 and 2013. During the study, particulate matter 15dN values ranged from 0.8 to 17.4‰, and 13dC values from −26.4 to −15.6‰over the region. We used spatial autocorrelation analysis and random forest modeling to examine the spatial trends and potential environmental drivers of the stable isotope values. We observed general trends toward lower values for both nitrogen and carbon isotopes at the seaward edge of the shelf. Conversely, higher 15dN and 13dC values were observed on the landward edge of the shelf, in particular in the southern portion of the sampling area. Across all sites, the magnitude of the difference between the 15dN of subsurface and surface particulate m

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

International Nuclear Information System (INIS)

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

2013-01-01

Highlights: • Treatability and C fractionation of 1,1,1-TCA by base-catalyzed S 2 O 8 2− was studied. • The rate of degradation of 1,1,1-TCA increased with a higher OH − :S 2 O 8 2− ratio. •Base-catalyzed S 2 O 8 2− can potentially treat recalcitrant compound like 1,1,1-TCA. • An enrichment factor of −7.0‰ independent of the OH − :S 2 O 8 2− ratio was obtained. • Carbon isotope can potentially be used to estimate the ISCO treatment efficacy. -- Abstract: The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S 2 O 8 2− ) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S 2 O 8 2− molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of ∼5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S 2 O 8 2− molar ratio of −7.0 ± 0.2‰ was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S 2 O 8 2− molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system

Investigating Pathways of Nutrient and Energy Flows Through Aquatic Food Webs Using Stable Isotopes of Carbon and Nitrogen

Energy Technology Data Exchange (ETDEWEB)

Hadwen, W. L.; Bunn, S. E. [Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan Campus, Brisbane, Queensland (Australia)

2013-05-15

Carbon and nitrogen stable isotopes can provide valuable insights into pathways of nutrient and energy flows in aquatic ecosystems. Carbon stable isotopes are principally used to trace pathways of organic matter transfer through aquatic food webs, particularly with regard to identifying the dominant sources of nutrition for aquatic biota. Stable isotopes of carbon have been widely used to answer one of the most pressing questions in aquatic food web ecology - to what degree do in-stream (autochthonous) and riparian (allochthonous) sources of energy fuel riverine food webs? In conjunction with carbon stable isotopes, nitrogen stable isotopes have been used to determine the trophic position of consumers and to identify the number of trophic levels in aquatic food webs. More recently, stable nitrogen isotopes have been recommended as indicators of anthropogenic disturbances. Specifically, agricultural land uses and/or sewage effluent discharge have been shown to significantly increase {delta}{sup 15}N signatures in primary producers and higher order consumers in freshwater, estuarine and marine environments. Together, carbon and nitrogen stable isotopes can be used to examine natural food web functions as well as the degree to which human modifications to catchments and aquatic environments can influence aquatic ecosystem function. (author)

The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

Science.gov (United States)

Heuer, Verena B.; Pohlman, John W.; Torres, Marta E.; Elvert, Marcus; Hinrichs, Kai-Uwe

2009-01-01

Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron

Magnetic and Geochemical Records of Glacial Terminations, Weathering and Carbon Burial in the Southeastern South China Sea for the Last 800 kyr

Science.gov (United States)

Kandasamy, S.; Kao, S.; Hsu, S.; Lee, T.; Velasco, V. M.; Soon, W.; Chen, M.

2013-12-01

Rebuilding of past climate and oceanographic records from monsoon dominated Asia is of vital importance for understanding the causes and mechanisms of global and regional climate changes at orbital-millennial timescales. South China Sea (SCS) provides the best marine platform to investigate a number of paleoclimate and paleoceanographic problems on different timescales mainly because of high sedimentation rates, good preservation of microfossils and the location of SCS as a connector between the Western Pacific Warm Pool and the SE Asian monsoon. Here we investigate magnetic, geochemical and isotopic records from a piston core MD97-2142 rose from the southeastern SCS to understand the past glacial terminations, chemical weathering and carbon burial on orbital to millennial timescales for the last 800 kyr. Terrigenous content and Al/Ti ratio reveal higher terrigenous input during glacial periods and vice versa during interglacials. Proxies of chemical weathering reveal larger fluctuations between 150 and 500 kyr than that of the last 150 kyr. Records of C/N ratio and carbon isotope of total organic carbon (δ13CTOC) mimic each other with higher marine productivity during marine isotope stages (MIS) 8, 10 and 12. Enrichment factors of Mn and Mo (EF Mn and EF Mo) show roughly an opposite pattern with 1 in most odd MIS, whereas <~1 EF Mn was evident in even MIS, suggesting that the former condition was likely attributed to bottom water ventilation associated with high sea levels during interglacials. We found through two endmember mixing model of δ13CTOC that lower burial of terrigenous fraction of TOC (OCTERR) during glacial intervals (MIS 6, 8, 10 and 12), but vice versa during interglacial (MIS 7, 9 and 11) periods. Our bulk magnetic susceptibility (MS) time series documents the last seven glacial terminations (T1-T7) with distinctive behaviors of T4 and T6. Wavelet analysis of MS record exhibits statistically significant periodicity at 239 kyr, 142 kyr, 85 kyr, 45

Soil moisture effects on the carbon isotopic composition of soil respiration

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The carbon isotopic composition ( 13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the 13C of soil respiration, which suggests indir...

Carbon isotopes and concentrations in mid-oceanic ridge basalts

International Nuclear Information System (INIS)

Pineau, F.; Javoy, M.

1983-01-01

In order to estimate carbon fluxes at mid-ocean ridges and carbon isotopic compositions in the convective mantle, we have studied carbon concentrations and isotopic compositions in tholeiitic glasses from the FAMOUS zone (Mid-Atlantic Ridge at 36 0 N) and East Pacific Rise from 21 0 N (RITA zone) to 20 0 S. These samples correspond essentially to the whole spectrum of spreading rates (2-16 cm/yr). The contain: -CO 2 vesicles in various quantities (3-220 ppm C) with delta 13 C between -4 and -9per mille relative to PDB, in the range of carbonatites and diamonds. - Carbonate carbon (3-100 ppm C) with delta 13 C between -2.6 and -20.0per mille relative to PDB. - Dissolved carbon at a concentration of 170+-10 ppm under 250 bar pressure with delta 13 C from -9 to -21per mille relative to PDB. This dissolved carbon, not contained in large CO 2 vesicles, corresponds to a variety of chemical forms among which part of the above carbonates, microscopic CO 2 bubbles and graphite. The lightest portions of this dissolved carbon are extracted at low temperatures (400-600 0 C) whereas the CO 2 from the vesicles is extracted near fusion temperature. These features can be explained by outgassing processes in two steps from the source region of the magma: (1) equilibrium outgassing before the second percolation threshold, where micron size bubbles are continuously reequilibrated with the magma; (2) distillation after the second percolation threshold when larger bubbles travel faster than magma concentrations to the surface. The second step may begin at different depths apparently related to the spreading rate, shallower for fast-spreading ridges than for slow-spreading ridges. (orig./WL)

The effects of atmospheric [CO2] on carbon isotope fractionation and magnesium incorporation into biogenic marine calcite

Science.gov (United States)

Vieira, Veronica

1997-01-01

The influences of atmospheric carbon dioxide on the fractionation of carbon isotopes and the magnesium incorporation into biogenic marine calcite were investigated using samples of the calcareous alga Amphiroa and benthic foraminifer Sorites grown in the Biosphere 2 Ocean system under variable atmospheric CO2 concentrations (approximately 500 to 1200 ppm). Carbon isotope fractionation was studied in both the organic matter and the skeletal carbonate. Magnesium analysis was to be performed on the carbonate removed during decalcification. These data have not been collected due to technical problems. Carbon isotope data from Amphiroa yields a linear relation between [CO2] and Delta(sup 13)C(sub Corg)values suggesting that the fractionation of carbon isotopes during photosynthesis is positively correlated with atmospheric [CO2]. [CO2] and Delta(sup 13)C(sub Corg) values for Sorites produce a relation that is best described by a hyperbolic function where Delta(sup 13)C(sub Corg) values increase between 300 and 700 ppm and decrease from 700 to 1200 ppm. Further investigation of this relation and Sorites physiology is needed.

Elemental and isotopic (C, O, Sr, Nd) compositions of Late Paleozoic carbonated eclogite and marble from the SW Tianshan UHP belt, NW China: Implications for deep carbon cycle

Science.gov (United States)

Zhu, Jianjiang; Zhang, Lifei; Lü, Zeng; Bader, Thomas

2018-03-01

Subduction zones are important for understanding of the global carbon cycle from the surface to deep part of the mantle. The processes involved the metamorphism of carbonate-bearing rocks largely control the fate of carbon and contribute to local carbon isotopic heterogeneities of the mantle. In this study, we present petrological and geochemical results for marbles and carbonated eclogites in the Southwestern Tianshan UHP belt, NW China. Marbles are interlayered with coesite-bearing pelitic schists, and have Sr-Nd isotopic values (εNd (T=320Ma) = -3.7 to -8.9, 87Sr/86Sr (i) = 0.7084-0.7089), typical of marine carbonates. The marbles have dispersed low δ18OVSMOW values (ranging from 14 to 29‰) and unaffected carbon isotope (δ13CVPDB = -0.2-3.6‰), possibly due to infiltration of external H2O-rich fluids. Recycling of these marbles into mantle may play a key role in the carbon budget and contributed to the mantle carbon isotope heterogeneity. The carbonated eclogites have high Sr isotopic compositions (87Sr/86Sr (i) = 0.7077-0.7082) and positive εNd (T = 320 Ma) values (from 7.6 to 8.2), indicative of strong seafloor alteration of their protolith. The carbonates in the carbonated eclogites are mainly dolomite (Fe# = 12-43, Fe# = Fe2+/(Fe2+ + Mg)) that were added into oceanic basalts during seafloor alteration and experienced calcite - dolomite - magnesite transformation during the subduction metamorphic process. The uniformly low δ18O values (∼11.44‰) of carbonates in the carbontaed eclogites can be explained by closed-system equilibrium between carbonate and silicate minerals. The low δ13C values (from -3.3 to -7.7‰) of the carbonated eclogites most likely reflect contribution from organic carbon. Recycling of these carbonated eclogites with C isotope similar to typical mantle reservoirs into mantle may have little effect on the mantle carbon isotope heterogeneity.

Carnivore specific bone bioapatite and collagen carbon isotope fractionations: Case studies of modern and fossil grey wolf populations

Science.gov (United States)

Fox-Dobbs, K.; Wheatley, P. V.; Koch, P. L.

2006-12-01

Stable isotope analyses of modern and fossil biogenic tissues are routinely used to reconstruct present and past vertebrate foodwebs. Accurate isotopic dietary reconstructions require a consumer and tissue specific understanding of how isotopes are sorted, or fractionated, between trophic levels. In this project we address the need for carnivore specific isotope variables derived from populations that are ecologically well- characterized. Specifically, we investigate the trophic difference in carbon isotope values between mammalian carnivore (wolf) bone bioapatite and herbivore (prey) bone bioapatite. We also compare bone bioapatite and collagen carbon isotope values collected from the same individuals. We analyzed bone specimens from two modern North American grey wolf (Canis lupus) populations (Isle Royale National Park, Michigan and Yellowstone National Park, Wyoming), and the ungulate herbivores that are their primary prey (moose and elk, respectively). Because the diets of both wolf populations are essentially restricted to a single prey species, there were no confounding effects due to carnivore diet variability. We measured a trophic difference of approximately -1.3 permil between carnivore (lower value) and herbivore (higher value) bone bioapatite carbon isotope values, and an average inter-tissue difference of 5.1 permil between carnivore bone collagen (lower value) and bioapatite (higher value) carbon isotope values. Both of these isotopic differences differ from previous estimates derived from a suite of African carnivores; our carnivore-herbivore bone bioapatite carbon isotope spacing is smaller (-1.3 vs. -4.0 permil), and our carnivore collagen-bioapatite carbon difference is larger (5.1 vs. 3.0 permil). These discrepancies likely result from comparing values measured from a single hypercarnivore (wolf) to average values calculated from several carnivore species, some of which are insectivorous or partly omnivorous. The trophic and inter

Descriptions of carbon isotopes within the energy density functional theory

Energy Technology Data Exchange (ETDEWEB)

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

2014-10-24

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

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

Science.gov (United States)

Porowska, Dorota

2015-05-01

Chemical and isotopic analyses of groundwater from piezometers located around a reclaimed landfill in Otwock (Poland) were performed in order to trace the origin of dissolved inorganic carbon (DIC) in the groundwater. Due to differences in the isotopic composition of carbon from different sources, an analysis of stable carbon isotopes in the groundwater, together with the Keeling plot approach and a two-component mixing model allow us to evaluate the relative contributions of carbon from these sources in the groundwater. In the natural (background) groundwater, DIC concentrations and the isotopic composition of DIC (δ(13)CDIC) comes from two sources: decomposition of organic matter and carbonate dissolution within the aquifer sediments, whereas in the leachate-contaminated groundwater, DIC concentrations and δ(13)CDIC values depend on the degradation of organic matter within the aquifer sediments and biodegradation of organic matter stored in the landfill. From the mixing model, about 4-54% of the DIC pool is derived from organic matter degradation and 96-46% from carbonate dissolution in natural conditions. In the leachate-contaminated groundwater, about 20-53% of the DIC is derived from organic matter degradation of natural origin and 80-47% from biodegradation of organic matter stored in the landfill. Partial pressure of CO2 (P CO2) was generally above the atmospheric, hence atmospheric CO2 as a source of carbon in DIC pool was negligible in the aquifer. P CO2 values in the aquifer in Otwock were always one to two orders of magnitude above the atmospheric P CO2, and thus CO2 escaped directly into the vadose zone. Copyright © 2015 Elsevier Ltd. All rights reserved.

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Directory of Open Access Journals (Sweden)

Niels J de Winter

Full Text Available The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-09-15

Highlights: • Treatability and C fractionation of 1,1,1-TCA by base-catalyzed S{sub 2}O{sub 8}{sup 2−} was studied. • The rate of degradation of 1,1,1-TCA increased with a higher OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio. •Base-catalyzed S{sub 2}O{sub 8}{sup 2−} can potentially treat recalcitrant compound like 1,1,1-TCA. • An enrichment factor of −7.0‰ independent of the OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio was obtained. • Carbon isotope can potentially be used to estimate the ISCO treatment efficacy. -- Abstract: The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S{sub 2}O{sub 8}{sup 2−}) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of ∼5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio of −7.0 ± 0.2‰ was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system.

The Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2) in the Western Interior US and Gulf of Mexico: Decoupled Black Shale Deposition and Carbon Isotope Excursion

Science.gov (United States)

Lowery, C.; Snedden, J.; Cunningham, R.; Barrie, C.; Leckie, R. M.

2016-12-01

The largest carbon isotope excursions (CIEs) of the Cretaceous are associated with widespread evidence for marine anoxia and have been termed Oceanic Anoxic Events (OAEs). OAEs were originally thought to be globally-correlative intervals of black shales, but black shale deposition is an inherently provincial phenomenon driven by local conditions, and black shales associated with individual OAEs are often slightly diachronous and can be absent in some regions. Workers currently favor a definition of OAEs that is focused on the positive carbon isotope excursion driven by the global burial of organic matter and resulting carbon cycle perturbation; i.e., recording the global, rather than local, changes. While this is certainly the best way to define a global event, differences in the expression of the event between regions can be used to study the nature of the event itself. The greater Gulf of Mexico region in southern North America offers an excellent example of the diachroneity of black shale deposition and anoxia during one of the largest OAEs, the Cenomanian-Turonian OAE2. The Western Interior Seaway (WIS), flooded the interior of North America from the Gulf of Mexico up through the Canadian Arctic. In Texas and elsewhere across the WIS, high marine organic matter deposition and proxies for anoxia (especially benthic foraminifera and redox sensitive trace metals) are common before the event, but decrease at its onset, and in some places increase again after the event. Further south, across the Mexican shelf, deeper shelf environments remain dysoxic/anoxic through the event, while several carbonate platforms remain oxygenated during the event, but drown and record anoxic bottom waters shortly afterward. Here, we present new bulk carbonate and organic carbon isotopes and planktic and benthic foraminiferal populations from a 90 m core in southern Mississippi, USA, to present the first record of OAE2 from the northern Gulf of Mexico. In particular, we use

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

Science.gov (United States)

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

2017-12-01

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

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

NARCIS (Netherlands)

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

2014-01-01

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

Reconstruction of limnology and microbialite formation conditions from carbonate clumped isotope thermometry.

Science.gov (United States)

Petryshyn, V A; Lim, D; Laval, B L; Brady, A; Slater, G; Tripati, A K

2015-01-01

Quantitative tools for deciphering the environment of microbialite formation are relatively limited. For example, the oxygen isotope carbonate-water geothermometer requires assumptions about the isotopic composition of the water of formation. We explored the utility of using 'clumped' isotope thermometry as a tool to study the temperatures of microbialite formation. We studied microbialites recovered from water depths of 10-55 m in Pavilion Lake, and 10-25 m in Kelly Lake, spanning the thermocline in both lakes. We determined the temperature of carbonate growth and the (18)O/(16)O ratio of the waters that microbialites grew in. Results were then compared to current limnological data from the lakes to reconstruct the history of microbialite formation. Modern microbialites collected at shallow depths (11.7 m) in both lakes yield clumped isotope-based temperatures of formation that are within error of summer water temperatures, suggesting that clumped isotope analyses may be used to reconstruct past climates and to probe the environments in which microbialites formed. The deepest microbialites (21.7-55 m) were recovered from below the present-day thermoclines in both lakes and yield radioisotope ages indicating they primarily formed earlier in the Holocene. During this time, pollen data and our reconstructed water (18)O/(16)O ratios indicate a period of aridity, with lower lake levels. At present, there is a close association between both photosynthetic and heterotrophic communities, and carbonate precipitation/microbialite formation, with biosignatures of photosynthetic influences on carbonate detected in microbialites from the photic zone and above the thermocline (i.e., depths of generally <20 m). Given the deeper microbialites are receiving <1% of photosynthetically active radiation (PAR), it is likely these microbialites primarily formed when lower lake levels resulted in microbialites being located higher in the photic zone, in warm surface waters. © 2014 John

Geological factors of the isotopic distribution of carbon of organic matter in sedimentary rocks

International Nuclear Information System (INIS)

Maass, J.

1981-01-01

The isotope ratio of carbon of fossile organic matter can be regarded as a definite criterion of its genetic origin. As the biofacial character of organic matter, especially the chemical composition (H/C-ratio), decisively influences the mode and quantity of the potential hydrocarbon production, isotopic analysis is an essential method for the prognostic evaluation of sedimentary basins with regard to their oil and gas perspectives. The genetic relations to the parent substance continue in the bituminization and coalification products and make it possible to apply the isotopic analysis of carbon to prospection work for hydrocarbons. (author)

The synthesis of a tritium, carbon-14, and stable isotope-labeled cathepsin C inhibitors.

Science.gov (United States)

Allen, Paul; Bragg, Ryan A; Caffrey, Moya; Ericsson, Cecilia; Hickey, Michael J; Kingston, Lee P; Elmore, Charles S

2017-02-01

As part of a medicinal chemistry program aimed at developing a highly potent and selective cathepsin C inhibitor, tritium, carbon-14, and stable isotope-labeled materials were required. The synthesis of tritium-labeled methanesulfonate 5 was achieved via catalytic tritiolysis of a chloro precursor, albeit at a low radiochemical purity of 67%. Tritium-labeled AZD5248 was prepared via a 3-stage synthesis, utilizing amide-directed hydrogen isotope exchange. Carbon-14 and stable isotope-labeled AZD5248 were successfully prepared through modifications of the medicinal chemistry synthetic route, enabling the use of available labeled intermediates. Copyright © 2016 John Wiley & Sons, Ltd.

Diagenetic fractionation of carbon isotopes in particulate and dissolved organic matter in sediments from Skan Bay, Alaska

International Nuclear Information System (INIS)

Alperin, M.J.; Reeburgh, W.S.

1991-01-01

Isotope fractionation during organic matter diagenesis was investigated by measuring detailed depth distributions of stable carbon isotope ratios in sediment particulate organic carbon (POC) and dissolved organic carbon (DOC) reservoirs. The δ 13 C value of the POC shifted systematically from -19 per-thousand at the surface to -21 per-thousand at 10 cm. Significant trends were also apparent in the δ 13 C-DOC profile. Proceeding down-core, DOC became isotopically heavier between 0 and 5 cm and isotopically lighter at greater depths. Two mechanisms could account for the observed down-core shift in δ 13 C-POC: (a) temporal changes in the isotope ratios of deposited organic matter and (b) isotope fractionation associated with diagenesis. The δ 15 C-DOC depth distribution is sensitive to which mechanism controls the isotopic composition of the POC reservoir. A diagenetic model that couples POC and DOC reservoirs was used to discriminate between temporal changes and diagenetic alteration of the POC isotopic composition. The model indicated that observed trends in δ 13 C-POC and δ 13 C-DOC depth distributions are consistent with isotopic fractionation of POC during diagenesis

Carbon isotope fractionation in the mangrove Avicennia marina has implications for food web and blue carbon research

Science.gov (United States)

Kelleway, Jeffrey J.; Mazumder, Debashish; Baldock, Jeffrey A.; Saintilan, Neil

2018-05-01

The ratio of stable isotopes of carbon (δ13C) is commonly used to track the flow of energy among individuals and ecosystems, including in mangrove forests. Effective use of this technique requires understanding of the spatial variability in δ13C among primary producer(s) as well as quantification of the isotopic fractionations that occur as C moves within and among ecosystem components. In this experiment, we assessed δ13C variation in the cosmopolitan mangrove Avicennia marina across four sites of varying physico-chemical conditions across two estuaries. We also compared the isotopic values of five distinct tissue types (leaves, woody stems, cable roots, pneumatophores and fine roots) in individual plants. We found a significant site effect (F3, 36 = 15.78; P 3.0‰) means that it may now be possible to partition the individual contributions of various mangrove tissues to estuarine food webs. Similarly, the contributions of mangrove leaves, woody debris and belowground sources to blue carbon stocks might also be quantified. Above all, however, our results emphasize the importance of considering appropriate mangrove tissue types when using δ13C to trace carbon cycling in estuarine systems.

A high-resolution carbon-isotope record of the Turonian stage correlated to a siliciclastic basin fill: Implications for mid-Cretaceous sea-level change

Czech Academy of Sciences Publication Activity Database

Uličný, David; Jarvis, I.; Gröcke, D. R.; Čech, S.; Laurin, Jiří; Olde, K.; Trabucho-Alexandre, J.; Švábenická, L.; Pedentchouk, N.

2014-01-01

Roč. 405, July (2014), s. 42-58 ISSN 0031-0182 R&D Projects: GA ČR GAP210/10/1991; GA MŠk LA08036 Institutional support: RVO:67985530 Keywords : eustasy * carbon isotopes * Bohemian Cretaceous Basin * Turonian * greenhouse climate * sequence stratigraphy Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.339, year: 2014

Carbon and oxygen isotopic composition of coal and carbon dioxide derived from laboratory coal combustion: A preliminary study

Science.gov (United States)

Warwick, Peter D.; Ruppert, Leslie F.

2016-01-01

The concentration of carbon dioxide (CO2) in the atmosphere has dramatically increased from the start of the industrial revolution in the mid-1700s to present levels exceeding 400 ppm. Carbon dioxide derived from fossil fuel combustion is a greenhouse gas and a major contributor to on-going climate change. Carbon and oxygen stable isotope geochemistry is a useful tool to help model and predict the contributions of anthropogenic sources of CO2 in the global carbon cycle. Surprisingly few studies have addressed the carbon and oxygen isotopic composition of CO2 derived from coal combustion. The goal of this study is to document the relationships between the carbon and oxygen isotope signatures of coal and signatures of the CO2 produced from laboratory coal combustion in atmospheric conditions.Six coal samples were selected that represent various geologic ages (Carboniferous to Tertiary) and coal ranks (lignite to bituminous). Duplicate splits of the six coal samples were ignited and partially combusted in the laboratory at atmospheric conditions. The resulting coal-combustion gases were collected and the molecular composition of the collected gases and isotopic analyses of δ13C of CO2, δ13C of CH4, and δ18O of CO2 were analysed by a commercial laboratory. Splits (~ 1 g) of the un-combusted dried ground coal samples were analyzed for δ13C and δ18O by the U.S. Geological Survey Reston Stable Isotope Laboratory.The major findings of this preliminary work indicate that the isotopic signatures of δ13C (relative to the Vienna Pee Dee Belemnite scale, VPDB) of CO2 resulting from coal combustion are similar to the δ13CVPDB signature of the bulk coal (− 28.46 to − 23.86 ‰) and are not similar to atmospheric δ13CVPDB of CO2 (~ − 8 ‰, see http://www.esrl.noaa.gov/gmd/outreach/isotopes/c13tellsus.html). The δ18O values of bulk coal are strongly correlated to the coal dry ash yields and appear to have little or no influence on the δ18O values of CO2

The thermal history of char as disclosed by carbon isotope ratios

DEFF Research Database (Denmark)

Egsgaard, Helge; Ambus, Per; Ahrenfeldt, Jesper

In laboratory experiments, biomass char was produced under controlled conditions using wood chips from French pinewood. Different char qualities were obtained by pyrolysing the biomass at similar heating rates with end-temperatures ranging from 250 to 1000 o C. The char was analysed by flash...... pyrolysis and isotope ratio mass spectrometry. The results demonstrate that the temperature history of the char is reflected in the fine variation of carbon isotopes. The compound classes responsible for the variation were identified. Key words: Isotope ratio, flash pyrolysis, hot gas cleaning...

Lead isotopic composition of paleozoic and late proterozoic marine carbonate rocks in the vicinity of Yucca Mountains, Nevada

International Nuclear Information System (INIS)

Zartman, R.E.; Kwak, L.M.

1993-01-01

Paleozoic and Late Proterozoic marine carbonate rocks (limestones, dolomites, and their metamorphic equivalents) cropping out in the vicinity of Yucca Mountain contain lead with an isotopic composition strongly suggesting them to be a major source of the lead observed at Trench 14 in the carbonate phase of carbonate-silica veins and nearby surficial calcrete deposits. Six whole-rock samples of marine carbonate rocks yield 206 Pb/ 204 Pb = 19.21-29.06, 207 Pb/ 204 Pb = 15.74-16.01, and 208 Pb/ 204 Pb = 37.90-39.25, and leachate and residue fractions of the rocks reveal additional isotopic heterogeneity within individual samples. Two samples of eolian dust also have isotopic compositions lying along a 'carbonate' to 'silicate' mixing trend that appears to arise entirely from pedeogenic processes. The tendency for the marine carbonate rocks to evolve highly uranogenic, but not thorogenic, lead results in a distinctive isotopic composition that serves as a tracer in eolian dust and secondary carbonate minerals derived from the marine carbonate rocks

A 40 ka high-resolution soil carbonate record from southern Utah: proxy development, paleohydrology, and paleoecology

Science.gov (United States)

Huth, T.; Cerling, T. E.; Marchetti, D. W.; Fernandez, D. P.; Mackey, G. N., III; Bowling, D. R.; Passey, B. H.

2017-12-01

Terrestrial paleoclimate records are critically important for testing hypotheses of climate dynamics and verifying climate simulations. However, unlike their oceanic counterparts, terrestrial records are short, more commonly discontinuous, and require specific geographic conditions not necessarily ideal for proposed questions (e.g., speleothem records must come from wherever a cave occurs). We instead utilize laminated soil carbonate rinds as a high resolution (100s yr) paleoclimate archive. Soil carbonate rinds can represent 10s-100s kyr, are apparently continuous over relevant timescales, maintain stratigraphic order, and are common in arid and semi-arid regions. We demonstrate the utility of this methodology at Torrey, Utah which is at the northern edge of the North American Monsoon (NAM). Sample rinds form on the bottom of large (≈1 m) boulders. The rinds are 0.5-2 cm thick and have visually and microscopically identifiable stratigraphy. Radiocarbon dates are in order and suggest a nearly constant growth rate from ≈40 ka to 3 ka, when the record ends. However, the pendants have significant pore space, so secondary carbonate has the potential to bias sample ages to be too young by 100s-1000s years. Precise sampling may be able to mitigate this bias. In spite of the potential secondary carbonate bias, δ13C and δ18O analyses show trends consistent with regional records. Secondary carbonate is therefore a concern, but apparently does not overpower the primary isotopic signals. A calibration study identified soil carbonate formation during the peak growing season (i.e., JAS, during the NAM), so we interpret our records as summer signals modulated by soil `memory' effects. The δ18O record has low variability (±0.5 ‰) but mimics regional NAM records, suggesting similar climate drivers as far north as Utah. The δ13C record shows some correlation with δ18O, which is reasonable given that the strength of the NAM can drive ecologic responses. However, the data

Control strategies for laser separation of carbon isotopes

Indian Academy of Sciences (India)

Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the ...

Elemental and stable isotopic approaches for studying the organic and inorganic carbon components in natural samples

International Nuclear Information System (INIS)

Helie, J-F

2009-01-01

The carbon cycle is an important part of major biogeochemical cycles. Many techniques may be used to characterize carbon amounts and sources in the environment. Here we first review the most popular techniques for the determination of organic and inorganic carbon concentrations. Decarbonatation techniques are also reviewed in details since it is often an important part of organic carbon analysis. The second part of this paper addresses the use of carbon stable isotopes to characterize organic carbon sources and processes in the environment. An overview of general stable isotopes background and terminology is given as well as the most popular analytical techniques.

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

Science.gov (United States)

Hodgin, E. B.

2015-12-01

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

Unravelling spatiotemporal tree-ring signals in Mediterranean oaks: a variance-covariance modelling approach of carbon and oxygen isotope ratios.

Science.gov (United States)

Shestakova, Tatiana A; Aguilera, Mònica; Ferrio, Juan Pedro; Gutiérrez, Emilia; Voltas, Jordi

2014-08-01

Identifying how physiological responses are structured across environmental gradients is critical to understanding in what manner ecological factors determine tree performance. Here, we investigated the spatiotemporal patterns of signal strength of carbon isotope discrimination (Δ(13)C) and oxygen isotope composition (δ(18)O) for three deciduous oaks (Quercus faginea (Lam.), Q. humilis Mill. and Q. petraea (Matt.) Liebl.) and one evergreen oak (Q. ilex L.) co-occurring in Mediterranean forests along an aridity gradient. We hypothesized that contrasting strategies in response to drought would lead to differential climate sensitivities between functional groups. Such differential sensitivities could result in a contrasting imprint on stable isotopes, depending on whether the spatial or temporal organization of tree-ring signals was analysed. To test these hypotheses, we proposed a mixed modelling framework to group isotopic records into potentially homogeneous subsets according to taxonomic or geographical criteria. To this end, carbon and oxygen isotopes were modelled through different variance-covariance structures for the variability among years (at the temporal level) or sites (at the spatial level). Signal-strength parameters were estimated from the outcome of selected models. We found striking differences between deciduous and evergreen oaks in the organization of their temporal and spatial signals. Therefore, the relationships with climate were examined independently for each functional group. While Q. ilex exhibited a large spatial dependence of isotopic signals on the temperature regime, deciduous oaks showed a greater dependence on precipitation, confirming their higher susceptibility to drought. Such contrasting responses to drought among oak types were also observed at the temporal level (interannual variability), with stronger associations with growing-season water availability in deciduous oaks. Thus, our results indicate that Mediterranean deciduous

Changes of stable isotopes carbon-13 and nitrogen-15 in different tissues of cattle

International Nuclear Information System (INIS)

Sun Fengmei; Yu Hongxia; Wu Wei; Yang Shuming

2009-01-01

Stable isotope analysis is a potential tool for tracing food origin. The stable carbon and nitrogen isotope composition in different tissues of two varieties of cattle under the same culture condition were investigated. δ 13 C and δ 15 N values of different defatted muscle and crude fat, cattle tail hair, blood, liver and feed were determined by isotope ratio mass spectrometry, and statistical analysis was carried out. The results showed that stable isotopes of carbon and nitrogen composition was not affected by cattle variety; the δ 13 C values between different defatted muscle, blood, liver and cattle hair were not significantly different, but δ 15 N value in the liver was much higher than other muscle and the δ 13 C values didn't show difference among all the crude fat samples. So these results indicated that isotope fractionation in the various tissue was discrepant. (authors)

Uranium Isotopes in Calcium Carbonate: A Possible Proxy for Paleo-pH and Carbonate Ion Concentration?

Science.gov (United States)

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

2015-12-01

Natural variations of 238U/235U in marine carbonates are being explored as a paleoredox proxy. However, in order for this proxy to be robust, it is important to understand how pH and alkalinity affect the fractionation of 238U/235U during coprecipitation with calcite and aragonite. Recent work suggests that the U/Ca ratio of foraminiferal calcite may vary with seawater [CO32-] concentration due to changes in U speciation[1]. Here we explore analogous isotopic consequences in inorganic laboratory co-precipitation experiments. Uranium coprecipitation experiments with calcite and aragonite were performed at pH 8.5 ± 0.1 and 7.5 ± 0.1 using a constant addition method [2]. Dissolved U in the remaining solution was periodically collected throughout the experiments. Samples were purified with UTEVA resin and 238U/235U was determined using a 233U-236U double-spike and MC-ICP-MS, attaining a precision of ± 0.10 ‰ [3]. Small but resolvable U isotope fractionation was observed in aragonite experiments at pH ~8.5, preferentially enriching heavier U isotopes in the solid phase. 238U/235U of the dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00002 - 1.00009. In contrast, no resolvable U isotope fractionation was detected in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among dissolved U species is the most likely mechanism driving these isotope effects. Our quantitative model of this process assumes that charged U species are preferentially incorporated into CaCO3 relative to the neutral U species Ca2UO2(CO3)3(aq), which we hypothesize to have a lighter equilibrium U isotope composition than the charged U species. According to this model, the magnitude of U isotope fractionation should scale with the fraction of the neutral U species in the solution, in agreement with our experimental results. These findings suggest that U isotope variations in

Using Clumped Isotopes to Understand Early Diagenetic Processes in Carbonate Microbialites of Mid-Cretaceous Codó Formation, NE Brazil

Science.gov (United States)

Bahniuk, A. M.; Vasconcelos, C.; McKenzie, J. A.; Franca, A. B.; Matsuda, N.; Eiler, J.

2010-12-01

Recent studies of the sedimentological, stratigraphic and geochemical aspects of carbonate microbialites have been carried out to characterize the paleoenvironmental and hydrological conditions of deposition for the Aptian Codó Formation (Parnaíba Basin) and the time-equivalent Santana Formation (Araripe Basin). This environmental interpretation is of interest because these sediments record the early stages of the opening of the Equatorial Atlantic Ocean, as well as being potentially important reservoir rock. Specifically, clumped isotope thermometry has been applied to evaluate the growth temperatures of carbonate components in selected samples from both outcrop and drill core. Preliminary results of clumped isotope measurements provide paleotemperatures derived for dense stromatolitic fabrics drilled from outcrop samples of the Codó Formation which vary between 29 and 33°C. In contrast, the micritic matrix of the drill core samples of the Codó Formation indicates a temperature range from 30 to 48°C. The lower values for the outcrop samples may represent a primary or early diagenetic temperature signal preserved in the rock. Moreover, the micritic matrix from the Santana Formation drill core samples indicates paleotemperatures ranging from 40 to 68°C, which are slightly higher than those for all measured samples of the Codó Formation. We propose that the higher paleotemperatures for all drill core samples denote a diagenetic effect that occurred with sediment lithification processes during burial; that is, isotopic reequilibration at depth is reflected in the higher measured paleotemperatures. Increased paleotemperatures are probably present in some carbonate fabrics of the outcrop samples of the Codo Formation, which also underwent lithification, but this signal was missed by our inability to micro-sample primary or early diagenetic stromatolitic fabrics. Assuming that the outcrop samples of the Codó Formation preserve an original stable isotope signal

The features of the isotope composition of carbon in the Paleozoic and Mesozoic oils of Western Siberia

Energy Technology Data Exchange (ETDEWEB)

Golyshev, S.I.; Lebedena, L.V.

1984-01-01

The isotope composition of the carbon in the oils from the Mesozoic and Paleozoic deposits is measured. The variations in the isotope composition of carbon for the Paleozoic oils is between 27.5 and 30.8 percent, while for the oils from the lower Jurassic and Triassic levels it is between 27.7 and 31.2 percent and for the upper Jurassic oils it is between 30.1 and 34.5 percent. The dependence of the isotope composition of the carbon in the oils on the type of original organic matter and its metamorphosis conditions during lithogenesis is analyzed. A softening in the isotope composition of the carbon in the oils from the oceanic deposits relative to continental deposits is found, together with a genetic individualism of the oils from the Paleozoic deposits and their difference from the oils in the Mesozoic deposits.

Carbon-Isotopic Analysis of Individual Pigments by HPLC-Moving Wire-IRMS

Science.gov (United States)

Sessions, A. L.; Keely, B. J.; Hayes, J. M.

2003-12-01

We have developed a method for directly analyzing the carbon isotope ratios of individual pigments, including chlorophyll (chl) and its derivatives, by coupling a high-performance liquid chromatograph (HPLC) to an isotope-ratio mass spectrometer (IRMS) via a novel `moving-wire' interface. Pigments were separated on a reversed-phase C18 column, using a binary gradient modified from Airs et al. (2001, J. Chrom. A 917, 167-177). The HPLC effluent was dried onto a continuously-spooling nickel wire, and the involatile sample residue was combusted to CO2 and transferred to the IRMS for isotopic analysis. Replicate analyses of a standard solution yield precision for delta13C of better than 0.2‰ for injections containing ~5 μ g of chl-a. A five-fold improvement in sensitivity should be attainable using capillary HPLC to further reduce solvent volumes. The biomarker potential of tetrapyrrole pigments, combined with the geochemical information recorded by isotopic compositions, makes this combination a potent tool for biogeochemical studies. As a demonstration, we analyzed chlorophyll degradation products in sediments from a lake and a salina. First, compounds derived from bacteriochlorophylls (bchl)-c and -d were extracted from sediment cores taken at Kirisjes Lake (Larsmann Hills, Antarctica). These pigments are products of green sulfur bacteria and indicate the presence of an anoxic photic zone. The δ 13C values of bchl-related compounds are near -25‰ . Using published fractionations for Chlorobium species to extrapolate, dissolved CO2 in Kirisjes Lake probably had a δ 13C value of -12 to -21‰ and was strongly influenced by the recycling of organic carbon, possibly including methane. Second, compounds derived from chl-a, bchl-c, and bchl-d were isolated from sediments taken below a living microbial mat in the hypersaline les Salines de la Trinital (South Catalonia, Spain). The sediments contain visible remnants of past microbial mats and pigment distributions

Stable carbon and nitrogen isotopes in vertical peat profiles of natural and drained boreal peatlands

Science.gov (United States)

Nykänen, Hannu; Mpamah, Promise; Rissanen, Antti; Pitkänen, Aki; Turunen, Jukka; Simola, Heikki

2015-04-01

Peatlands form a significant carbon pool in the global carbon cycle. Change in peat hydrology, due to global warming is projected to change microbiological processes and peat carbon pool. We tested if bulk stable carbon and nitrogen isotopes serve as indicators of severe long term drying in peatlands drained for forestry. Depth profile analysis of peat, for their carbon and nitrogen content as well as their carbon and nitrogen stable isotopic signatures, were conducted for peatlands in southern and eastern Finland, having ombrotrophic and minerotrophic natural and corresponding drained pairs or separate drained sites. The selection of sites allowed us to compare changes due to different fertility and changes due to long term artificial drying. Drainage lasting over 40 years has led to changes in hydrology, vegetation, nutrient mineralization and respiration. Furthermore, increased nutrient uptake and possible recycling of peat nitrogen and carbon trough vegetation back to the peat surface, also possibly has an effect on the stable isotopic composition of peat carbon and nitrogen. We think that drainage induced changes somehow correspond to those caused by changed hydrology due to climate change. We will present data from these measurements and discuss their implications for carbon and nitrogen flows in peatlands.

Isotopic investigation of the late neoproterozoic and early cambrian carbon cycle on the northern Yangtze platform, south China

International Nuclear Information System (INIS)

Guo Qingjun; Liu Congqiang; Harald Strauss; Tatiana Goldberg

2003-01-01

The Precambrian-Cambrian transition is one of the critical time intervals in Earth history. Profound geotectonic, climatic and biological changes occur during the late Neoproterozoic and its transition into the early Cambrian. This study has researched on paired carbonate and organic carbon isotope determinations from Nanjiang, Sichuan Province of the Yangtze Platform, and provided a preliminary geochemical explanation for environmental variations and bio-events observed on the northern Yangtze Platform during the Precambrian-Cambrian transitional interval and their causal relationship. Organic carbon isotopic compositions on sediments vary from -35.8 to -30.1‰ at Nanjiang section; carbonate carbon isotopic compositions change between -3.5 and +0.5‰. Various carbon and sulphur isotopic compositions, different pyrite and organic matter content reflect changing environment and burial of organic matter in the Dengying Fm., the lower and upper part of Niutitang Fm. Anoxic conditions result in widespread preservation of organic rich sediments and pyrites in the black shales on the Yangtze Platform. (authors)

Application of carbon isotope stratigraphy to late miocene shallow marine sediments, new zealand.

Science.gov (United States)

Loutit, T S; Kennett, J P

1979-06-15

A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River, New Zealand, and correlated with a similar shift in Late Miocene Deep Sea Drilling Project sequences throughout the Indo-Pacific. A dated piston core provides an age for the shift of 6.2 +/- 0.1 million years. Correlations based on the carbon isotopic change require a revision of the previously established magnetostratigraphy at Blind River. The carbon shift at Blind River occurs between 6.2 and 6.3 +/- 0.1 million years before present. A new chronology provides an age for the evolutionary first appearance datum of Globorotalia conomiozea at 6.1 +/- 0.1 million years, the beginning of a distinct latest Miocene cooling event associated with the Kapitean stage at 6.2 +/- 0.1 million years, and the beginning of a distinct shallowing of water depths at 6.1 +/- 0.1 million years. The Miocene-Pliocene boundary as recognized in New Zealand is now dated at 5.3 +/- 0.1 million years. Extension of carbon isotope stratigraphy to other shallow Late Miocene sequences should provide an important datum for international correlation of Late Miocene shallow and deep marine sequences.

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

Science.gov (United States)

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

2007-06-01

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

Stable carbon isotope ratios: implications for the source of sediment carbon and for phytoplankton carbon assimilation in Lake Memphremagog, Quebec

International Nuclear Information System (INIS)

LaZerte, B.D.

1983-01-01

The stable carbon isotope (SCI) ratio of the sediment of Lake Memphremagog, Quebec is compared with that ot terrestrial sources and the phytoplankton to determine the relative proportion of allochthonous carbon incorporated into the sediments. Approximately 40-50% of the organic carbon in the main basins' pelagic sediment was terrestrial in origin, whereas up to 100% was terrestrial in littoral areas. The SCI method of determining the organic carbon source of sediments appears more reliable than the C/N method. A comparison of the SCI fractionation of the phytoplankton with laboratory cultures under different degrees of carbon limitation indicates that the phytoplankton of Lake Memphremagog are not carbon limited and fix carbon primarily by the C 3 pathway

Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition

International Nuclear Information System (INIS)

Zielinski, M.; Zielinska, A.; Papiernik-Zielinska, H.; McKenzie, J.A.; Bernasconi, S.; Paul, H.

1998-01-01

Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition above and below its melting temperature have been studied and compared with the primary (PKIE) and secondary kinetic isotope effects (SKIE) of 13 C and 18 O, respectively, in the decarboxylation of other heterocyclic acids. The temperature dependence of the secondary oxygen-18 isotope effects is negative in the total 221-255 deg C temperature interval investigated initially. The 13 C KIE measured above melting point of N.A. (temperature interval 235-270 deg C) are located in the range 1.007-1.009. Below melting point of nicotinic acid the 13 C KIE are larger and reveal the negative temperature dependence ( 13 C KIE decreases with decreasing the reaction temperature from 1.013/at 230 deg C to 1.0114/at 221 deg C). A discussion of the above isotopic results is presented. (author)

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

NARCIS (Netherlands)

van Roij, Linda; Sluijs, Appy; Laks, Jelmer J.; Reichart, Gert-Jan

2017-01-01

Rationale: Analyses of stable carbon isotope ratios (δ13C values) of organic and inorganic matter remains have been instrumental for much of our understanding of present and past environmental and biological processes. Until recently, the analytical window of such analyses has been limited to

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

DEFF Research Database (Denmark)

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

2011-01-01

The use of stable isotopes in diet analysis usually relies on the different photosynthetic pathways of C3 and C4 plants, and the resulting difference in carbon isotope signature. In the Arctic, however, plant species are exclusively C3, and carbon isotopes alone are therefore not suitable......% graminoids and up to 20% willows. In conclusion, the diet composition of an arctic herbivore can indeed be inferred from stable isotopes in arctic areas, despite the lack of C4 plants...... for studying arctic herbivore diets. In this study, we examined the potential of both stable carbon and nitrogen isotopes to reconstruct the diet of an arctic herbivore, here the muskox (Ovibos moschatus (Zimmermann, 1780)), in northeast Greenland. The isotope composition of plant communities and functional...

Thallium isotope evidence for a permanent increase in marine organic carbon export in the early Eocene

Science.gov (United States)

Nielsen, S.G.; Mar-Gerrison, S.; Gannoun, A.; LaRowe, D.; Klemm, V.; Halliday, A.N.; Burton, K.W.; Hein, J.R.

2009-01-01

The first high resolution thallium (Tl) isotope records in two ferromanganese crusts (Fe-Mn crusts), CD29 and D11 from the Pacific Ocean are presented. The crusts record pronounced but systematic changes in 205Tl/203Tl that are unlikely to reflect diagenetic overprinting or changes in isotope fractionation between seawater and Fe-Mn crusts. It appears more likely that the Fe-Mn crusts track the Tl isotope composition of seawater over time. The present-day oceanic residence time of Tl is estimated to be about 20,000??yr, such that the isotopic composition should reflect ocean-wide events. New and published Os isotope data are used to construct age models for these crusts that are consistent with each other and significantly different from previous age models. Application of these age models reveals that the Tl isotope composition of seawater changed systematically between ~ 55??Ma and ~ 45??Ma. Using a simple box model it is shown that the present day Tl isotope composition of seawater depends almost exclusively on the ratio between the two principal output fluxes of marine Tl. These fluxes are the rate of removal of Tl from seawater via scavenging by authigenic Fe-Mn oxyhydroxide precipitation and the uptake rate of Tl during low temperature alteration of oceanic crust. It is highly unlikely that the latter has changed greatly. Therefore, assuming that the marine Tl budget has also not changed significantly during the Cenozoic, the low 205Tl/203Tl during the Paleocene is best explained by a more than four-fold higher sequestration of Tl by Fe-Mn oxyhydroxides compared with at the present day. The calculated Cenozoic Tl isotopic seawater curve displays a striking similarity to that of S, providing evidence that both systems may have responded to the same change in the marine environment. A plausible explanation is a marked and permanent increase in organic carbon export from ~ 55??Ma to ~ 45??Ma, which led to higher pyrite burial rates and a significantly reduced

Soil moisture effects on the carbon isotope composition of soil respiration

Science.gov (United States)

Claire L. Phillips; Nick Nickerson; David Risk; Zachary E. Kayler; Chris Andersen; Alan Mix; Barbara J. Bond

2010-01-01

The carbon isotopic composition (δ13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the δ13C of soil respiration, which suggests indirectly that recently fixed photosynthates...

Carbon isotope variations in the upper Carboniferous - Permian Mallemuk Mountain Group, eastern North Greenland

International Nuclear Information System (INIS)

Stemmerik, L.; Magaritz, M.

1989-01-01

Isotope data from Late Palaeozoic limestones of the Wandel Sea Basin in eastern North Greenland show a variation of δ 13 C from 0.0 0/00 to 5.7 0/00 vs PDB. Carbonates depleted in 13 C occur in the basal part of lower Moscovian, upper Moscovian and middle Gzhelian transgressive sequences. 13 C enriched limestones occur later in the cycles. The most 13 C enriched limestones occur in the youngest (late Early Permian-early Late Permian) part of the sequence in Amdrup Land. The isotopic data is believed to represent changes in the global carbon cycle. Thus 13 C enriched carbonates correlate to periods of burial of organic carbon mostly as coal, while 13 C depleted carbonates formed as the result of erosion and oxidation of organic carbon during sea-level low stands. (author)

Stable carbon and oxygen isotope studies of Late Weichselian lake sediments in southern Sweden and northern Poland, with palaeoclimatic implications

International Nuclear Information System (INIS)

Hammarlund, D.

1994-04-01

Late Weichselian lacustrine sediment sequences from southern Sweden and northern Poland were studied by means of stable isotope analysis in order to reconstruct the climatic development and climatically induced environmental changes in the respective regions. The methods used include analyses of the stable carbon isotope composition (δ 13 C) of bulk organic material, and the stable carbon and oxygen isotope compositions (δ 13 C, δ 18 O) of bulk carbonates and carbonate shells of aquatic organisms. These results were complemented and supported by lithological, chemical and biostratigraphic data (plant macrofossils, insects, molluscs). Chronological data were obtained by AMS radiocarbon dates and correlations based on pollen analysis. At c. 12.400 BP a climatic change from arctic, dry, and continental, to subarctic and more humid and maritime conditions occurred in southern Sweden. The Older Dryas stadial (c.12.200-12.000 BP) is characterized by a temporary return to generally colder , drier, and more continental conditions, followed by generally favourable (subarctic), although unstable, climatic conditions. At c. 11.300 BP a gradual transition towards a colder and more continental climate was initiated, followed by total absence of limnic carbonates during the Younger Dryas stadial (c. 11.000-10.200 BP), indicating arctic and continental conditions. The transition to the Holocene is characterized by a rapid and strong climatic warming. The results from northern Poland point to some important differences compared to this development. A climatic warming around 13.000 BP was followed by generally favourable climatic conditions enabling continuous sedimentation of limnic carbonates during the Late Weichselian. Distinct depletions of 13 C in lacustrine organic material at the transition to the Holocene were recorded in southern Sweden, also demonstrated by decreasing mean values obtained from an extensive compilation of δ 13 C data. A number of processes that may

A carbon isotope survey of South African honey

International Nuclear Information System (INIS)

Thorp, J.A.L.; Lanham, J.L.; Wenner, D.B.; Van der Merwe, N.J.

1987-01-01

Stable carbon isotope analysis has been successfully employed in various fields, including botany, geochemistry, archaeology and, more recently, as an analytical tool in the food industry. In the analysis of food, it has been primarily directed at quality control and the detection of cheap adulterants to 'natural' foods. The method is based on the known characteristic of differences in the 13 C to 12 C ratios produced by two groups of plants with different photosynthetic mechanisms, known as C 3 and C 4 . This patterning is useful because the cheapest sources of alcohol, sweeteners and flavourings are derived from C 4 plants, maize and sugar cane, whereas traditional Old World sources such as grapes, nectar and fruit are derived from C 3 plants. The results of an informal isotopic survey of South African honeys are reported. This isotopic method is particularly useful in that it is not possible to circumvent it by manipulation of the sugars or any of the other constituents

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

Science.gov (United States)

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

2017-12-01

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

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

Directory of Open Access Journals (Sweden)

K. R. Lassey

2007-01-01

Full Text Available Little is known about how the methane source inventory and sinks have evolved over recent centuries. New and detailed records of methane mixing ratio and isotopic composition (12CH4, 13CH4 and 14CH4 from analyses of air trapped in polar ice and firn can enhance this knowledge. We use existing bottom-up constructions of the source history, including "EDGAR"-based constructions, as inputs to a model of the evolving global budget for methane and for its carbon isotope composition through the 20th century. By matching such budgets to atmospheric data, we examine the constraints imposed by isotope information on those budget evolutions. Reconciling both 12CH4 and 13CH4 budgets with EDGAR-based source histories requires a combination of: a greater proportion of emissions from biomass burning and/or of fossil methane than EDGAR constructions suggest; a greater contribution from natural such emissions than is commonly supposed; and/or a significant role for active chlorine or other highly-fractionating tropospheric sink as has been independently proposed. Examining a companion budget evolution for 14CH4 exposes uncertainties in inferring the fossil-methane source from atmospheric 14CH4 data. Specifically, methane evolution during the nuclear era is sensitive to the cycling dynamics of "bomb 14C" (originating from atmospheric weapons tests through the biosphere. In addition, since ca. 1970, direct production and release of 14CH4 from nuclear-power facilities is influential but poorly quantified. Atmospheric 14CH4 determinations in the nuclear era have the potential to better characterize both biospheric carbon cycling, from photosynthesis to methane synthesis, and the nuclear-power source.

Isotopic-spectral determination of hydrogen, nitrogen, oxygen and carbon in semiconductor materials

International Nuclear Information System (INIS)

Dudich, G.K.; Eremeev, V.A.; Li, V.N.; Nemets, V.M.

1981-01-01

Techniques of low-temperature isotopic-spectral determination of impurities of hydrogen, nitrogen, oxygen and carbon in semiconductor materials Bi, Ge, Pb tellurides are developed. The techniques include selection into special vessel with the known volume (exchanger) of sample analyzed, dosed introduction into exchanger of rare isotope of the element determined ( 2 H, 15 N, 18 O, 13 C) in the form of isotope-containing gas, balancing of the determined element isotopes in the system sample-isotope, containing gas, spectroscopic, determination of its isotope composition in gaseous phase of the system and calculation of the amount of the element determined in the sample. The lower boundaries of the amounts determined constitute 10 -7 , 10 -7 , 10 -6 and 10 -5 mass % respectively when sample of 20 g are used [ru

GasBench/isotope ratio mass spectrometry: a carbon isotope approach to detect exogenous CO(2) in sparkling drinks.

Science.gov (United States)

Cabañero, Ana I; San-Hipólito, Tamar; Rupérez, Mercedes

2007-01-01

A new procedure for the determination of carbon dioxide (CO(2)) (13)C/(12)C isotope ratios, using direct injection into a GasBench/isotope ratio mass spectrometry (GasBench/IRMS) system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. Thirty-nine commercial sparkling drink samples from various origins were analyzed. Values of delta(13)C(cava) ranged from -20.30 per thousand to -23.63 per thousand, when C3 sugar addition was performed for a second alcoholic fermentation. Values of delta(13)C(water) ranged from -5.59 per thousand to -6.87 per thousand in the case of naturally carbonated water or water fortified with gas from the spring, and delta(13)C(water) ranged from -29.36 per thousand to -42.09 per thousand when industrial CO(2) was added. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO(2) addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows (13)C/(12)C determination directly from a liquid sample without previous CO(2) extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase. Copyright (c) 2007 John Wiley & Sons, Ltd.

Carbon isotope fractionation by sulfate-reducing bacteria using different pathways for the oxidation of acetate.

Science.gov (United States)

Goevert, Dennis; Conrad, Ralf

2008-11-01

Acetate is a key intermediate in the anaerobic degradation of organic matter. In anoxic environments, available acetate is a competitive substrate for sulfate-reducing bacteria (SRB) and methane-producing archaea. Little is known about the fractionation of carbon isotopes by sulfate reducers. Therefore, we determined carbon isotope compositions in cultures of three acetate-utilizing SRB, Desulfobacter postgatei, Desulfobacter hydrogenophilus, and Desulfobacca acetoxidans. We found that these species showed strong differences in their isotope enrichment factors (epsilon) of acetate. During the consumption of acetate and sulfate, acetate was enriched in 13C by 19.3% per hundred in Desulfobacca acetoxidans. By contrast, both D. postgatei and D. hydrogenophilus showed a slight depletion of 13C resulting in epsilon(ac)-values of 1.8 and 1.5% per hundred, respectively. We suggest that the different isotope fractionation is due to the different metabolic pathways for acetate oxidation. The strongly fractionating Desulfobacca acetoxidans uses the acetyl-CoA/carbon monoxide dehydrogenase pathway, which is also used by acetoclastic methanogens that show a similar fractionation of acetate (epsilon(ac) = -21 to -27% per hundred). In contrast, Desulfobacter spp. oxidize acetate to CO2 via the tricarboxylic acid (TCA) cycle and apparently did not discriminate against 13C. Our results suggestthat carbon isotope fractionation in environments with sulfate reduction will strongly depend on the composition of the sulfate-reducing bacterial community oxidizing acetate.

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

DEFF Research Database (Denmark)

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

produced carbonate shells (bivalves, gastropods) and corals. Our preliminary data set ranges approximately from d53Cr = -0.2 to +0.7‰. They are isotopically lighter than local seawater. This is in good agreement with [6], who measured a negative offset from seawater in corals. These offsets indicate some...

Simulation of dual carbon-bromine stable isotope fractionation during 1,2-dibromoethane degradation.

Science.gov (United States)

Jin, Biao; Nijenhuis, Ivonne; Rolle, Massimo

2018-06-01

We performed a model-based investigation to simultaneously predict the evolution of concentration, as well as stable carbon and bromine isotope fractionation during 1,2-dibromoethane (EDB, ethylene dibromide) transformation in a closed system. The modelling approach considers bond-cleavage mechanisms during different reactions and allows evaluating dual carbon-bromine isotopic signals for chemical and biotic reactions, including aerobic and anaerobic biological transformation, dibromoelimination by Zn(0) and alkaline hydrolysis. The proposed model allowed us to accurately simulate the evolution of concentrations and isotope data observed in a previous laboratory study and to successfully identify different reaction pathways. Furthermore, we illustrated the model capabilities in degradation scenarios involving complex reaction systems. Specifically, we examined (i) the case of sequential multistep transformation of EDB and the isotopic evolution of the parent compound, the intermediate and the reaction product and (ii) the case of parallel competing abiotic pathways of EDB transformation in alkaline solution.

Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

Directory of Open Access Journals (Sweden)

J. Jung

2011-11-01

Full Text Available In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E in East Asia, total suspended particles (TSP were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC, total nitrogen (TN, and stable carbon isotopic composition (δ¹³C of TC. The stable carbon isotopic composition of TC (δ¹³C_TC was found to be lowest during pollen emission episodes (range: −26.2‰ to −23.5‰, avg. −25.2 ± 0.9‰, approaching those of the airborne pollen (−28.0‰ collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ¹³C_TC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C. Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

Stable carbon isotopic composition of gasolines determined by isotope ratio monitoring gas chromatography mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Smallwood, B.J.; Philp, R.P.; Allen, J.D. [University of Oklahoma, Norman, OK (United States). School of Geology and Geophysics

2002-07-01

A large number of underground gasoline storage facilities in the United States continuously leak gasoline into the subsurface, which makes gasoline a major groundwater contaminant. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) are used currently to characterize contaminated groundwater and soils. Correlations of contaminants with suspected source(s) are extremely difficult by these techniques because many gasolines have similar hydrocarbon distributions. The present study applied the technique of isotope ratio monitoring gas chromatography-mass spectrometry (irmGC-MS) to 19 gasoline samples from different areas of the USA. This allows a much better correlation of gasoline contaminants to source. Data obtained indicate a wide range of {sup {delta}}{sup 13}C values for 16 ubiquitous compounds in the gasolines. The majority of samples could be distinguished from each other on the basis of {sup {delta}}{sup 13}C hydrocarbon composition. The oxygenated additive methyl tertiary butyl ether (MTBE) was present in ten of the gasolines analyzed, and had a relatively narrow range of {sup {delta}}{sup 13}C values (-30.4 to -28.3 per mille). Preliminary investigations were also made to determine the extent of carbon isotopic fractionation after simple water washing and evaporation experiments. Results indicate that the majority of compounds did not undergo significant carbon isotopic fractionation as a result of these processes. (author)

Thermodynamics of calcium-isotope-exchange reactions. 1. Exchange between isotopic calcium carbonates and aqueous calcium ions

International Nuclear Information System (INIS)

Zhang, R.S.; Nash, C.P.; Rock, P.A.

1988-01-01

This paper reports the authors results for the direct experimental determination of the equilibrium constant for the calcium-isotope-exchange reaction 40 CaCO 3 (s) + 44 CaCl 2 (aq) reversible 44 CaCO 2 (s) + 40 CaCl 2 (aq). The reaction was studied in electrochemical double cells without liquid junction of the type shown in eq 2. The experimental value of the equilibrium constant at 295 +/- 2 K is K = 1.08 +/- 0.02. The experimental value for K is compared with the values of K calculated for various model reactions according to the statistical thermodynamic theory of isotope effects. The isotopic solid carbonates were modeled according to both the Debye and Kieffer theories. No structured models of solvated isotopic aqueous calcium ions yield calculated equilibrium constants in agreement with their experimental results. This conclusion is in agreement with published molecular dynamics calculations which show that the aqueous solvation of Ca 2 =(aq) is essentially unstructured

The relationship between carbon stable isotope ratios of hatchling down and egg yolk in Black-headed Gulls

NARCIS (Netherlands)

Klaassen, M.R.J.; Baarspul, T.; Dekkers, T.; Van Tienen, P.

2004-01-01

We reconstructed the nutrient source for egg synthesis by sampling Black-headed Gull (Larus ridibundus) eggs for yolk, analyzing their carbon stable isotope ratio, and comparing that to hatchling down. Most of the variation in carbon stable isotope ratio was explained by differences between nests,

Water relations link carbon and oxygen isotope discrimination to phloem sap sugar concentration in eucalyptus globulus

International Nuclear Information System (INIS)

Cernusak, L.A.; Farquhar, G.D.; Arthur, D.J; Pate, J.S.

2002-01-01

Full text: The carbon isotope ratio of phloem sap sugars has been previously observed to correlate strongly with the phloem sap sugar concentration in Eucalyptus globulus. We hypothesized that the correspondence between these two parameters results from co-linearity in their responses to variation in plant water potential. Carbon isotope discrimination is expected to decrease with decreasing plant water potential due to the influence of stomatal conductance on the ratio of intercellular to ambient CO 2 , concentrations (c 1 /c a ). Conversely, we expected the phloem sap sugar concentration to increase with decreasing plant water potential, thereby maintaining positive turgor pressure within the sieve tubes. The study comprised 40 individual Eucalyptus globulus trees growing in three plantations situated on opposing ends of a rainfall gradient in southwestern Australia. A strong correlation was observed between the carbon isotope ratio in phloem sap sugars and phloem sap sugar concentration. Carbon isotope discrimination correlated positively with shoot water potential, whereas phloem sap sugar concentration correlated negatively with shoot water potential. The relationship between carbon isotope discrimination measured in phloem sap sugars collected from the stem and c 1 /c a measured instantaneously on subtending leaves was close to that theoretically predicted. Accordingly, a strong, negative relationship was observed between instantaneous c 1 /c a and the phloem sap sugar concentration. Oxygen isotope discrimination in phloem sap sugars also correlated strongly with phloem sap sugar concentration. A theoretical model suggested that the observed variation in stomatal conductance was sufficient to account for the variation observed in oxygen isotope discrimination across the study. Results strongly support the contention that water relations form a mechanistic link between phloem sap sugar concentration and both instantaneous and integrated measures of the

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

International Nuclear Information System (INIS)

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

1985-01-01

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

Riverine Carbon and the Sedimentary Record on the Continental Shelves

Science.gov (United States)

2005-09-30

focused on the Gulf of Lions: collecting sediment samples and carrying out elemental and stable carbon isotopic analysis . The field work was carried...organisms. For example, the predominance of nitrogen-free biomacromolecules (e.g. tannin , lignin, cellulose, cutin and suberin) over proteins (C:N ≈ 3-4...are cooperating with J. Fabres and A. Calafat (CRG Marine Geosciences) in carrying out elemental and isotopic analysis on suspended material

Diamond carbon sources: a comparison of carbon isotope models

International Nuclear Information System (INIS)

Kirkley, M.B.; Otter, M.L.; Gurney, J.J.; Hill, S.J.

1990-01-01

The carbon isotope compositions of approximately 500 inclusion-bearing diamonds have been determined in the past decade. 98 percent of these diamonds readily fall into two broad categories on the basis of their inclusion mineralogies and compositions. These categories are peridotitic diamonds and eclogitic diamonds. Most peridotitic diamonds have δ 13 C values between -10 and -1 permil, whereas eclogitic diamonds have δ 13 C values between -28 and +2 permil. Peridotitic diamonds may represent primordial carbon, however, it is proposed that initially inhomogeneous δ 13 C values were subsequently homogenized, e.g. during melting and convection that is postulated to have occurred during the first billion years of the earth's existence. If this is the case, then the wider range of δ 13 C values exhibited by eclogitic diamonds requires a different explanation. Both the fractionation model and the subduction model can account for the range of observed δ 13 C values in eclogitic diamonds. 16 refs., 2 figs

Modelling the 13C and 12C isotopes of inorganic and organic carbon in the Baltic Sea

Science.gov (United States)

Gustafsson, Erik; Mörth, Carl-Magnus; Humborg, Christoph; Gustafsson, Bo G.

2015-08-01

In this study, 12C and 13C contents of all carbon containing state variables (dissolved inorganic and organic carbon, detrital carbon, and the carbon content of autotrophs and heterotrophs) have for the first time been explicitly included in a coupled physical-biogeochemical Baltic Sea model. Different processes in the carbon cycling have distinct fractionation values, resulting in specific isotopic fingerprints. Thus, in addition to simulating concentrations of different tracers, our new model formulation improves the possibility to constrain the rates of processes such as CO2 assimilation, mineralization, and air-sea exchange. We demonstrate that phytoplankton production and respiration, and the related air-sea CO2 fluxes, are to a large degree controlling the isotopic composition of organic and inorganic carbon in the system. The isotopic composition is further, but to a lesser extent, influenced by river loads and deep water inflows as well as transformation of terrestrial organic carbon within the system. Changes in the isotopic composition over the 20th century have been dominated by two processes - the preferential release of 12C to the atmosphere in association with fossil fuel burning, and the eutrophication of the Baltic Sea related to increased nutrient loads under the second half of the century.

Carbon Isotopic Ratios of Amino Acids in Stardust-Returned Samples

Science.gov (United States)

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

2009-01-01

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

A Comparison of Recent Organic and Inorganic Carbon Isotope Records: Why Do They Covary in Some Settings and Not In Others?

Science.gov (United States)

Oehlert, A. M.; Swart, P. K.

2013-12-01

Covariance between inorganic and organic δ13C records has been used to determine whether a deposit has been altered by diagenesis, how the dynamics of the global carbon cycle changed during the production of the sediments in the deposit, and also for chronostratigraphic correlations. Although covariant records are observed in the ancient geologic record in a variety of depositional environments, such comparisons are not widely applied to modern deposits where definitive data regarding sediment producers, sea level fluctuations, and changes in the global carbon cycle are available. This study uses paired δ13C records from cores collected by the Ocean Drilling Program from three modern periplatform settings (the Great Bahama Bank, the Great Australian Bight, and the Great Barrier Reef), and two pelagic settings (the Walvis Ridge, and the Madingley Rise). These sites were selected in order to assess the influence of several different environmental factors including; sediment and organic matter producers, sediment mineralogy, margin architecture, sea level oscillations, and sediment transport pathways. In the three periplatform settings, multiple cores arranged in a margin to basin transect were analyzed in order to provide insights into the effects of downslope sediment transport. The preliminary results of this study suggest that sea level oscillations and margin architecture may artificially generate a covarying relationship in periplatform sediments that is unrelated to changes in the global carbon cycle. Furthermore, preliminary results from the Walvis Ridge and the Madingley Rise sediments suggest that the relationship between inorganic and organic δ13C records may not always exhibit a positive covariance as is currently assumed for pelagic carbonates.

Preliminary assessment of the grading of Eucalyptus clones using carbon isotope discrimination

International Nuclear Information System (INIS)

Bond, W.J.; Stock, W.D.

1990-01-01

Stable carbon isotopes were analysed in leaf material of nine Eucalyptus clones grown in field trials in the eastern Transvaal. Carbon isotope ratios, measured as d 13 C, differed within tree canopies, between replicate trees and between clones. Values from both north and south canopy positions were correlated with tree height after 13 months. Unexplained variation in the correlation may be interpreted, theoretically, as an indication that some clones use less water for the same level of productivity. With further testing, the method may have promise for early screening of clones in genotype/environment interaction trials and in selecting water-efficient trees. 3 figs., 3 tabs., 7 refs

Stable isotopes and their relationship to temperature and precipitation as recorded in low latitude ice cores

International Nuclear Information System (INIS)

Thompson, L.G.; Davis, M.E.; Pin-Nan, Lin

2002-01-01

The potential of stable isotopic ratios ( 18 O/ 16 O and 2 H/ 1 H) in mid to low latitude glaciers as modern tools for paleoclimate reconstruction is reviewed. The isotopic composition of precipitation should be viewed not only as a powerful proxy indicator of climate, but also as an additional parameter for understanding climate-induced changes in the water cycle, on both regional and global scales. To interpret quantitatively the ice core isotopic records, the response of the isotopic composition of precipitation to long-term fluctuations of key climatic parameters (temperature, precipitation amount, relative humidity) over a given area should be known. Furthermore, it is important to establish the transfer functions that relate the climate-induced changes of the isotopic composition of precipitation to the isotope record preserved in the glacier. The factors that govern the values of stable isotopes in snowfall are enigmatic and as yet no satisfactory model has been developed to link them directly with any one meteorological or oceanographic factor. This is particularly problematic in the high altitude glaciers in the tropics, where complications are present due not only to continental effects, but also to altitude effects and convective air mass instability, particularly in the monsoon climates of the tropics. This paper presents long and short-term perspectives of isotopic composition variations in ice cores spanning the last 25,000 years from the mid- to low-latitude glaciers. The isotopic records will also be examined as a function of the altitude of the individual coring sites which ranges from 5325 meters to 7200 meters. On the short, term isotopic records from ice cores from the Andes of South America, the Tibetan Plateau and Kilimanjaro in Africa through the year 2000 will be presented. All the tropical glaciers for which data exist are disappearing, and these sites show isotopic enrichment in the 20th century that suggests that large scale low latitude

Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

International Nuclear Information System (INIS)

Zielinski, M.; Czarnota, G.; Papiernik-Zielinska, H.; Kasprzyk, G.; Gumolka, L.; Staedter, W.

1993-01-01

The 13 C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphoric acids (PA) and by 85% H 3 PO 4 has been studied in the temperature interval of 60-150 deg C. The values of the 13 C (1) isotope effects in the decarbonylation of lactic acid in 100% H 3 PO 4 , in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C (1)- OH bond is broken in the rate-controlling step of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90-130 deg C the experimental 13 C fractionation factors determined in concentrated PA approach quite closely the 13 C fractionation corresponding to C (2)- C (1) bond scission. The 13 C (1) kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110-150 deg C coincide with the 13 C isotope effects calculated assuming that the frequency corresponding to the C (1) -OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H 3 PO 4 has been suggested. A possible secondary 18 O and a primary 18 O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too. (author) 21 refs.; 3 tabs

Stable isotope compositions of organic carbon and contents of ...

African Journals Online (AJOL)

The stable isotope compositions of organic carbon (OC), and contents of OC and nitrogen for four sediment cores recovered from lakes Makat (located in the Ngorongoro Crater), Ndutu and Masek (located in the Serengeti Plains) are used to document sources of organic matter (OM) and climatic changes in sub-arid ...

Studies of carbon--isotope fractionation. Annual progress report, December 1, 1974--November 30, 1975

International Nuclear Information System (INIS)

Ishida, T.

1975-01-01

The vapor pressure isotope effect of 13 C/ 12 C-substitution in CClF 3 was measured at temperatures between 169 0 and 206 0 K by means of cryogenic distillation. The 13 C/ 12 C-vapor pressure isotope effect in CHF 3 was also studied at temperatures between 161 0 and 205 0 K by a similar method. The construction of a cryostat has progressed as scheduled. The investigation of carbon isotope exchange equilibria between carbon dioxide and various carbamates dissolved in various organic solvents has continued. The five-stage system of Taylor-Ghate design was improved to shorten the transient time. A single stage apparatus was designed, built, and tested. These systems are used to measure the equilibrium constants and various phase equilibria involved in the carbon dioxide--carbamate system. The investigation of the explicit method of total isotope effect has made progress. A satisfactory approximation was found for the classical partition function of a Morse oscillator. The method gives a reasonable result at rho identical with 1 / 2 √(u/sub e//x/sub e/) greater than 1.5. The medium cluster approach was applied to isotopic methanes to investigate the effects of intermolecular distance and mutual orientations of molecules in the liquid upon vapor pressure isotope effect. It was found that all geometrical effects studied tend to vanish as the size of clusters is increased. Isotope effect in the zero-point energy shifts on condensation was calculated on the basis of London dispersion forces in liquid and a semi-empirical molecular orbital theory, and was favorably compared with experimental results

Stratigraphy and stable isotope geochemistry of the carbonate sequence from the Paraguay belt

International Nuclear Information System (INIS)

Santos, Roberto Ventura.; Alvarenga, Carlos Jose Souza de; Dantas, Elton Luiz

2001-01-01

Two main Neoproterozoic carbonate sequences occur central Brazil both of which are stratiphicaly above glacial derived sediments. An older carbonate sequence occurs over the Sao Francisco Craton and in the surrounding folded belts (Rio Preto, Aracuai Ribeira and Brasilia). These carbonates overlie glacial diamictites that were related to the 'Sturtian' event dated between 0.7 and 0.9 Ga (Toulkeridis et al. 1999, Santos et al., 2000). A second carbonate sequence is described in the Paraguay Belt and postdated Vendian/Varegian glaciation sediments from the end of the Neoproterozoic. This glacial event has been reported in many studies concerning the Gondwana and the Laurentia supercontinent (Trompette, 1996; Condon and Prave, 2000; Myrow and Kaufman, 1999). In the Paraguay Belt the Vendian- Varangian glaciation rocks are characterized by a glaciomarine sequence, that occur at the border of the basin, and by glacial derived turbidites deposits, that occur in the deeper parts of the basin (Alvarenga and Trompette, 1992). Near the city of Corumba this glaciomarine sequence is overlaid by carbonate rocks containing Ediacaran-like fauna in which has been described Corumbella werneri and Cloudina Lucianoi (Hahn et al., 1982; Walde et al., 1982; Zaine and Fairchild, 1985; 1987). These carbonates have been interpreted as cap carbonates and the age of their fossils have been attributed to the Vendian Superior (590-545 MA) (Alvarenga and Trompette, 1992, Trompette 1996). Isotope stratigraphy studies have been widely used to study cap carbonate rocks that overlie Sturtian and Vendian- Varagian glaciogenic rocks. Stratigraphic correlation of these units is usually difficult because their lack fossils and there is no precise dating method that could be applied to these rocks. Hence, most studies concerning Neoproterozoic carbonates have concentrated on their stromatilites and microfossils content as well as on carbon isotope variations. In the present study, we present new carbon

Temperature and composition of carbonate cements record early structural control on cementation in a nascent deformation band fault zone: Moab Fault, Utah, USA

Science.gov (United States)

Hodson, Keith R.; Crider, Juliet G.; Huntington, Katharine W.

2016-10-01

Fluid-driven cementation and diagenesis within fault zones can influence host rock permeability and rheology, affecting subsequent fluid migration and rock strength. However, there are few constraints on the feedbacks between diagenetic conditions and structural deformation. We investigate the cementation history of a fault-intersection zone on the Moab Fault, a well-studied fault system within the exhumed reservoir rocks of the Paradox Basin, Utah, USA. The fault zone hosts brittle structures recording different stages of deformation, including joints and two types of deformation bands. Using stable isotopes of carbon and oxygen, clumped isotope thermometry, and cathodoluminescence, we identify distinct source fluid compositions for the carbonate cements within the fault damage zone. Each source fluid is associated with different carbonate precipitation temperatures, luminescence characteristics, and styles of structural deformation. Luminescent carbonates appear to be derived from meteoric waters mixing with an organic-rich or magmatic carbon source. These cements have warm precipitation temperatures and are closely associated with jointing, capitalizing on increases in permeability associated with fracturing during faulting and subsequent exhumation. Earlier-formed non-luminescent carbonates have source fluid compositions similar to marine waters, low precipitation temperatures, and are closely associated with deformation bands. The deformation bands formed at shallow depths very early in the burial history, preconditioning the rock for fracturing and associated increases in permeability. Carbonate clumped isotope temperatures allow us to associate structural and diagenetic features with burial history, revealing that structural controls on fluid distribution are established early in the evolution of the host rock and fault zone, before the onset of major displacement.

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

Science.gov (United States)

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

2014-09-01

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

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

Science.gov (United States)

Dannoura, M.; Bosc, A.; Chipeaux, C.; Sartore, M.; Lambrot, C.; Trichet, P.; Bakker, M.; Loustau, D.; Epron, D.

2010-12-01

Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse labeling of whole crown was conducted at 4 seasons to study the fate of assimilated carbon by photosynthesis into the root on 12 year old Pinus pinaster planted in the INRA domain of Pierroton. Maritime pine is the most widely planted species in South-West Europe. Stem, root and soil CO2 effluxes and their isotope composition were measured continuously by tunable diode laser absorption spectroscopy with a trace gas analyzer (TGA 100A; Campbell Scientific) coupled to flow-through chambers. 13CO2 recovery and peak were observed in respiration of each compartment after labeling. It appeared sequentially from top of stem to bottom, and to coarse root. The maximum velocity of carbon transfer was calculated as the difference in time lag of recovery between two positions on the trunk or on the root. It ranged between 0.08-0.2 m h-1 in stem and between 0.04-0.12 m h-1 in coarse root. This velocity was higher in warmer season, and the difference between time lag of recovery and peak increased after first frost. Photosynthates arrived underground 1.5 to 5 days after labeling, at similar time in soil CO2 effluxes and coarse root respiration. 0.08-1.4 g of carbon was respired per tree during first 20 days following labeling. It presented 0.6 -10% of 13C used for labeling and it is strongly related to seasons. The isotope signal was detected in fine root organs and microbial biomass by periodical core sampling. The peak was observed 6 days after labeling in early summer while it was delayed more than 10 days in autumn and winter with less amount of carbon allocated

Strontium isotopes in carbonate deposits at Crater Flat, Nevada

International Nuclear Information System (INIS)

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

1991-01-01

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

Strontium isotopes in carbonate deposits at Crater Flat, Nevada

International Nuclear Information System (INIS)

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

1991-01-01

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

Evaluating the use of strontium isotopes in tree rings to record the isotopic signal of dust deposited on the Wasatch Mountains

International Nuclear Information System (INIS)

Miller, Olivia L.; Solomon, Douglas Kip; Fernandez, Diego P.; Cerling, Thure E.; Bowling, David R.

2014-01-01

Highlights: • Dust was a major contributor of Sr to soil and tree rings over Sr poor bedrocks. • Tree rings were evaluated for their use as a record of dust strontium isotope history. • The isotopic signal of dust deposited on the Wasatch Mountains changed over the past ∼75 years. - Abstract: Dust cycling from the Great Basin to the Rocky Mountains is an important component of ecological and hydrological processes. We investigated the use of strontium (Sr) concentrations and isotope ratios ( 87 Sr/ 86 Sr) in tree rings as a proxy for dust deposition. We report Sr concentrations and isotope ratios ( 87 Sr/ 86 Sr) from atmospherically deposited dust, soil, bedrock, and tree rings from the Wasatch Mountains to investigate provenance of dust landing on the Wasatch Mountains and to determine if a dust Sr record is preserved in tree rings. Trees obtained a majority of their Sr from dust, making them a useful record of dust source and deposition. Dust contributions of Sr to soils were more than 94% over quartzite, 63% over granodiorite, and 50% over limestone. Dust contributions of Sr to trees were more than 85% in trees growing over quartzite, 55% over granodiorite, and between 0% and 92% over limestone. These findings demonstrate that a dust signal was preserved in some tree rings and reflects how Sr from dust and bedrock mixes within the soil. Trees growing over quartzite were most sensitive to dust. Changes in Sr isotope ratios for a tree growing over quartzite were interpreted as changes in dust source over time. This work has laid the foundation for using tree rings as a proxy for dust deposition over time

Miocene isotope zones, paleotemperatures, and carbon maxima events at intermediate water-depth, Site 593, Southwest Pacific

International Nuclear Information System (INIS)

Cooke, P.J.; Nelson, C.S.; Crundwell, M.P.

2008-01-01

Oxygen and carbon isotopic stratigraphies are presented from both benthic and planktic foraminifera for the late early Miocene to earliest Pliocene interval (c. 19-5 Ma) of intermediate water-depth DSDP Site 593 in the southern Tasman Sea. The benthic values are interpreted as recording Miocene Southern Component Intermediate Water, while the planktic species record the Miocene mode and surface water signals. Comparisons are made between temperate Site 593 and the intermediate-depth polar Site 747 in the southern Indian Ocean. Glacial Mi zones Mi1b-Mi6, representing extreme glacial events, are evident in both the Site 593 intermediate and surface water records. Miocene Southern Component Intermediate Water δ 18 O values are generally lighter than the Holocene equivalent (Antarctic Intermediate Water), indicating slightly warmer intermediate waters and/ or less global ice volume. The benthic-planktic gradient is interpreted as indicating a less stratified Tasman Sea during the Miocene. The benthic δ 13 C record contains most of the global carbon maxima (CM) events, CM1-7 (CM1-6 = the Monterey Excursion). Like global deep-water records, the Tasman Sea intermediate water δ 13 C values indicate that most CM events correspond with Mi glacials, including Mi4 at Site 593, not reported previously. Intermediate waters play an important role in propagating climatic changes from the polar regions to the tropics, and the Site 593 dataset provides a full water column record of the structure of Miocene intermediate to surface watermasses prior to the modern situation. (author). 132 refs., 8 figs., 4 tabs

Coordinated Oxygen Isotopic and Petrologic Studies of CAIS Record Varying Composition of Protosolar

Science.gov (United States)

Simon, Justin I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

2012-01-01

Ca-, Al-rich inclusions (CAIs) record the O-isotope composition of Solar nebular gas from which they grew [1]. High spatial resolution O-isotope measurements afforded by ion microprobe analysis across the rims and margin of CAIs reveal systematic variations in (Delta)O-17 and suggest formation from a diversity of nebular environments [2-4]. This heterogeneity has been explained by isotopic mixing between the O-16-rich Solar reservoir [6] and a second O-16-poor reservoir (probably nebular gas) with a "planetary-like" isotopic composition [e.g., 1, 6-7], but the mechanism and location(s) where these events occur within the protoplanetary disk remain uncertain. The orientation of large and systematic variations in (Delta)O-17 reported by [3] for a compact Type A CAI from the Efremovka reduced CV3 chondrite differs dramatically from reports by [4] of a similar CAI, A37 from the Allende oxidized CV3 chondrite. Both studies conclude that CAIs were exposed to distinct, nebular O-isotope reservoirs, implying the transfer of CAIs among different settings within the protoplanetary disk [4]. To test this hypothesis further and the extent of intra-CAI O-isotopic variation, a pristine compact Type A CAI, Ef-1 from Efremovka, and a Type B2 CAI, TS4 from Allende were studied. Our new results are equally intriguing because, collectively, O-isotopic zoning patterns in the CAIs indicate a progressive and cyclic record. The results imply that CAIs were commonly exposed to multiple environments of distinct gas during their formation. Numerical models help constrain conditions and duration of these events.

Molecular and stable carbon isotopic characterization of PAH contaminants at McMurdo Station, Antarctica

International Nuclear Information System (INIS)

Kim, Moonkoo . E-mail moonkoo.kim@wmich.edu; Kennicutt, Mahlon C.; Qian Yaorong

2006-01-01

The molecular and stable carbon isotopic compositions of contaminant polycyclic aromatic hydrocarbons (PAHs) at McMurdo Station, Antarctica were analyzed in samples collected from land and sub-tidal area. PAHs in the study areas were characterized by high amounts of naphthalene and alkylated naphthalenes from petroleum products introduced by human activities in the area. Principal component analysis (PCA) of PAH composition data identified multiple sources of PAH contamination in the study area. Compositional assignments of origins were confirmed using compound specific stable carbon isotopic analysis

61 stable isotope compositions of organic carbon and contents of ...

African Journals Online (AJOL)

Mgina

isotope record from Lake Ndutu shows a general downcore decrease in δ. 13C values ... in bulk δ13C of the terrestrial biomass in the tropics may ... CO2, temperature, moisture conditions and ... A map showing location of sampling sites of Ngorongoro Crater, Lake Ndutu and .... the Lakes Makat and Masek records cannot.

Carbonate and carbon isotopic evolution of groundwater contaminated by produced water brine with hydrocarbons