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Sample records for carbon isotope excursions

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

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    Nikolay V. Sennikov

    2015-08-01

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

  2. Dissolved inorganic carbon isotope signatures in ferruginous lakes: new insights into ancient carbonate isotope excursions

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    Wittkop, C.; Swanner, E.; Lambrecht, N.; Torgeson, J.; Katsev, S.; Myrbo, A.

    2016-12-01

    Dissolved iron, nutrient, and oxygen profiles from two newly documented ferruginous lakes demonstrate their ability to serve as ancient ocean analogs. Profiles of δ13C composition of dissolved inorganic carbon (δ13CDIC) from eutrophic Brownie Lake in Minnesota and oligotrophic Canyon Lake in Michigan confirm features previously documented in ferruginous lakes: significant variability in δ13CDIC between surface, chemocline, and bottom waters, told by pronounced negative carbon isotope excursions at the chemocline, shifting to significant enrichments in deep waters. Dissolved methane concentrations and methane isotope compositions in Canyon Lake are consistent with pelagic anaerobic methane oxidation, which appears to be the dominant influence on δ13CDIC at the chemocline of this site. Microprobe data from paleo-ferruginous (Quaternary) lake sediments reveal the presence of zoned Fe-Mn carbonates in finely banded sediments where Fe-speciation data lack a magnetite signature associated with diagenetic dissimilatory iron reduction, suggestive of a water-column origin for some ferruginous carbonates. These field and sediment data are consistent with the hypothesis that carbonate δ13C signatures widely assumed to be diagenetic may also be attributed to processes that occur in a ferruginous water column. Carbonate precipitation at a ferruginous chemocline would yield depleted carbon isotope signatures similar to those imparted by diagenetic organic matter mineralization, while carbonate precipitation at a ferruginous sediment-water interface may yield significantly enriched carbon isotope signatures similar to those imparted by diagenetic methanogenesis. Careful evaluation of sediment texture and geochemistry is needed to discern the potential for water column isotopic signatures in ancient ferruginous carbonates. This model may be applied to enigmatic carbon isotope signatures recorded in Precambrian iron formation carbonates including the Kalahari Manganese Field

  3. Spatial isotopic heterogeneity during the Guttenberg isotopic carbon excursion: Mechanisms and implications for craton-wide isotope gradients

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    Metzger, J. G.; Fike, D. A.

    2012-12-01

    The carbon isotopic compositions of carbonate carbon (δ13Ccarb) and organic carbon (δ13Corg) in marine limestones are frequently used as paleoenvironmental proxies and as chemostratigraphic tools for aligning strata. These functions are predicated upon the assumption that isotopic variability in these strata reflects the secular variation in the marine reservoir of dissolved inorganic carbon (DIC). As such, the utility of these isotopic systems largely depends on the assumed spatial homogeneity of marine δ13CDIC. While other isotope systems such as sulfate and strontium have been shown to be extremely well mixed in the modern ocean, a 1-2‰ range in δ13CDIC exists over the entire depth and latitude range of the ocean. This variability in δ13CDIC is largely the result of differences in the local balance of organic carbon fixation and export (increasing δ13CDIC) and/or organic carbon oxidation (decreasing δ13CDIC). The preservation of such isotopic variability in the geologic record has been advocated on several occasions. In particular, previous workers have argued for an ocean-to-interior seaway isotopic gradient in δ13Ccarb, δ13Corg, and ɛNd across Laurentia during the Late Ordovician across the interval that spans the Guttenberg Isotopic Carbon Excursion (GICE). Here we examine two Late Ordovician-aged sections from Missouri, USA that contain the GICE. At first glace, our data showed high degree of stratigraphic and lateral variability. Detailed petrographic and geochemical (e.g., trace element abundance) screening reveals that the majority of the isotopic heterogeneity in our sections is the result of local syndepositional/diagenetic alteration - and not the result of primary gradients in δ13CDIC between the localities examined. Our 'least-altered' δ13Ccarb profile matches closely with previously published records from Iowa; however, sections adjacent both to our locations in Missouri and to the similar δ13Ccarb profile in Iowa are characterized by

  4. Oxygen-isotope trends and seawater temperature changes across the Late Cambrian Steptoean positive carbon-isotope excursion (SPICE event)

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    Elrick, M.; Rieboldt, S.; Saltzman, M.; McKay, R.M.

    2011-01-01

    The globally recognized Late Cambrian Steptoean positive C-isotope excursion (SPICE) is characterized by a 3???-5??? positive ??13C shift spanning thermohaline circulation rates contributed to decreased dissolved O2 concentrations, which enhanced the preservation/burial of Corg causing the positive ??13C shift. ?? 2011 Geological Society of America.

  5. Shuram–Wonoka carbon isotope excursion: Ediacaran revolution in the world ocean's meridional overturning circulation

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    George E. Williams

    2018-03-01

    Full Text Available The late Ediacaran Shuram–Wonoka excursion, with δ13Ccarb values as low as –12‰ (PDB in marine-shelf deposits and spanning up to 10 Myr, is the deepest and most protracted δ13Ccarb negative anomaly recognised in Earth history. The excursion formed on at least four continents in low (≤32° palaeolatitudes, and in China is associated with a major phosphogenic event. Global and intrabasinal correlation, magnetostratigraphy, isotope conglomerate tests and further geochemical data are consistent with a primary or syn-depositional origin for the excursion. Continental-margin phosphorites are generated by oceanic upwelling driven by surface winds, and δ13Ccarb negative anomalies are explicable by oceanic upwelling of 13C-depleted deep oceanic waters, arguing that a feature common to these exceptional Ediacaran events was unprecedented perturbation of the world ocean. These events occurred during the transition from an alien Proterozoic world marked by low-palaeolatitude glaciation near sea level and strong seasonality to the familiar Phanerozoic Earth with circum-polar glaciation and temperate climate, suggesting that the Shuram–Wonoka excursion is related to this profound change in Earth's climate system. Of various hypotheses for Proterozoic low-palaeolatitude glaciation, only the high obliquity (>54° hypothesis, which posits secular decrease in obliquity to near the present-day value (23.5° during the Ediacaran, predicts an unparalleled revolution in the Ediacaran world ocean. The obliquity controls the sense of the world ocean's meridional overturning circulation, which today is driven by the sinking of cold, dense water at the poles and upwelling driven by zonal surface winds. When the decreasing obliquity passed the critical value of 54° during the Ediacaran the meridional temperature gradient reversed, with the equator becoming warmer than the poles and Hadley low-latitude (<30°–35° atmospheric zonal circulation reversing

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

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

    2016-05-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere-ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event and also to correlate marine and terrestrial records with high precision. The Paleocene-Eocene Thermal Maximum (PETM) is well documented, but CIE records for the subsequent warming events are still rare, especially from the terrestrial realm.Here, we provide new paleosol carbonate CIE records for two of the smaller hyperthermal events, I1 and I2, as well as two additional records of Eocene Thermal Maximum 2 (ETM2) and H2 in the Bighorn Basin, Wyoming, USA. Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope history to the deep-sea benthic foraminiferal isotope records from Ocean Drilling Program (ODP) sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates the idea that the Bighorn Basin fluvial sediments record global atmospheric change. The ˜ 34 m thicknesses of the eccentricity-driven hyperthermals in these archives corroborate precession forcing of the ˜ 7 m thick fluvial overbank-avulsion sedimentary cycles. Using bulk-oxide mean-annual-precipitation reconstructions, we find soil moisture contents during the four younger hyperthermals that are similar to or only slightly wetter than the background, in contrast with soil drying observed during the PETM using the same proxy, sediments, and plant fossils.The magnitude of the CIEs in soil carbonate for the four smaller, post-PETM events scale nearly linearly with the equivalent event magnitudes documented in marine records. In contrast, the magnitude of the PETM terrestrial CIE is at least 5 ‰ smaller than expected based on extrapolation of the scaling relationship established

  7. Magnitude of the carbon isotope excursion at the Paleocene Eocene thermal maximum: The role of plant community change

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    Smith, Francesca A.; Wing, Scott L.; Freeman, Katherine H.

    2007-10-01

    Carbon-isotope measurements ( δ13C) of leaf-wax n-alkanes from the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, reveal a negative carbon isotope excursion (CIE) of 4-5‰, which is 1-2‰ larger than that observed in marine carbonate δ13C records. Reconciling these records requires either that marine carbonates fail to record the full magnitude of the CIE or that the CIE in plants has been amplified relative to the marine. Amplification of the CIE has been proposed to result from an increase in available moisture that allowed terrestrial plants to increase 13C-discrimination during the PETM. Leaf physiognomy, paleopedology and hydrogen isotope ratios of leaf-wax lipids from the Bighorn Basin, however, all suggest that rather than a simple increase in available moisture, climate alternated between wet and dry during the PETM. Here we consider two other explanations and test them quantitatively with the carbon isotopic record of plant lipids. The "marine modification" hypothesis is that the marine carbonate record was modified by chemical changes at the PETM and that plant lipids record the true magnitude of the CIE. Using atmospheric CO 2δ13C values estimated from the lipid record, and equilibrium fractionation between CO 2 and carbonate, we estimate the expected CIE for planktonic foraminifera to be 6‰. Instead, the largest excursion observed is about 4‰. No mechanism for altering marine carbonate by 2‰ has been identified and we thus reject this explanation. The "plant community change" hypothesis is that major changes in floral composition during the PETM amplified the CIE observed in n-alkanes by 1-2‰ relative to marine carbonate. This effect could have been caused by a rapid transition from a mixed angiosperm/conifer flora to a purely angiosperm flora. The plant community change hypothesis is consistent with both the magnitude and pattern of CIE amplification among the different n-alkanes, and with data from fossil plants

  8. A diagenetic control on the Early Triassic Smithian-Spathian carbon isotopic excursions recorded in the marine settings of the Thaynes Group (Utah, USA).

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    Thomazo, C; Vennin, E; Brayard, A; Bour, I; Mathieu, O; Elmeknassi, S; Olivier, N; Escarguel, G; Bylund, K G; Jenks, J; Stephen, D A; Fara, E

    2016-05-01

    In the aftermath of the end-Permian mass extinction, Early Triassic sediments record some of the largest Phanerozoic carbon isotopic excursions. Among them, a global Smithian-negative carbonate carbon isotope excursion has been identified, followed by an abrupt increase across the Smithian-Spathian boundary (SSB; ~250.8 Myr ago). This chemostratigraphic evolution is associated with palaeontological evidence that indicate a major collapse of terrestrial and marine ecosystems during the Late Smithian. It is commonly assumed that Smithian and Spathian isotopic variations are intimately linked to major perturbations in the exogenic carbon reservoir. We present paired carbon isotopes measurements from the Thaynes Group (Utah, USA) to evaluate the extent to which the Early Triassic isotopic perturbations reflect changes in the exogenic carbon cycle. The δ(13) Ccarb variations obtained here reproduce the known Smithian δ(13) Ccarb -negative excursion. However, the δ(13) C signal of the bulk organic matter is invariant across the SSB and variations in the δ(34) S signal of sedimentary sulphides are interpreted here to reflect the intensity of sediment remobilization. We argue that Middle to Late Smithian δ(13) Ccarb signal in the shallow marine environments of the Thaynes Group does not reflect secular evolution of the exogenic carbon cycle but rather physicochemical conditions at the sediment-water interface leading to authigenic carbonate formation during early diagenetic processes. © 2016 John Wiley & Sons Ltd.

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

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    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.

  10. Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene-Eocene Thermal Maximum record from central China

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    Chen, Zuoling; Wang, Xu; Hu, Jianfang; Yang, Shiling; Zhu, Min; Dong, Xinxin; Tang, Zihua; Peng, Ping'an; Ding, Zhongli

    2014-12-01

    The carbon isotope excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been recognized for the first time in the micritic carbonate, total organic carbon (TOC) and black carbon (BC) contained within the lacustrine sediments from the Nanyang Basin, central China. The remarkably large excursion (∼ - 6 ‰) in the δ13CTOC and δ13CBC values is possibly attributable to increased humidity and elevated pCO2 concentration. The ∼ - 4 ‰ CIE recorded in the δ13Ccalcite, reflecting the average isotope change of the watershed system, is consistent with that observed in planktonic foraminifera. This correspondence suggests that the true magnitude of the carbon isotope excursion in the ocean-atmosphere system is likely close to - 4 ‰. The ∼10 m excursion onset in our multi-proxy δ13C records demonstrates that the large input of 13C-depleted carbon into the ocean-atmosphere system was not geologically instantaneous. Despite difference and somewhat smoothness in detailed pattern of the CIE due to localized controls on different substrates, inorganic and organic δ13C data generally depict a gradual excursion onset at least over timescales of thousands of years. In addition, continental temperature reconstruction, based on the distribution of membrane lipids of bacteria, suggests a warming of ∼4 °C prior to the PETM and ∼7 °C increase in temperature during the PETM. The temperature data are overall similar in pattern and trend to the δ13C change across the PETM. These observations, combined with pre-CIE warming, are in line with the idea that 13C-depleted carbon release operated as a positive feedback to temperature, suggesting supply from one or more large organic carbon reservoirs on Earth's surface.

  11. Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: pCO2 and paleo productivity

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    J. S. Sinninghe Damsté

    2012-02-01

    Full Text Available A complete, well-preserved record of the Cenomanian/Turonian (C/T Oceanic Anoxic Event 2 (OAE-2 was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260. Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane (δ13Cphytane, a biomarker for photosynthetic algae. The δ13Cphytane record shows a positive excursion at the onset of the OAE-2 interval, with an unusually large amplitude (~7‰ compared to existing C/T proto-North Atlantic δ13Cphytane records (3–6‰. Overall, the amplitude of the excursion of δ13Cphytane decreases with latitude. Using reconstructed sea surface temperature (SST gradients for the proto-North Atlantic, we investigated environmental factors influencing the latitudinal δ13Cphytane gradient. The observed gradient is best explained by high productivity at DSDP Site 367 and Tarfaya basin before OAE-2, which changed in overall high productivity throughout the proto-North Atlantic during OAE-2. During OAE-2, productivity at site 1260 and 603B was thus more comparable to the mid-latitude sites. Using these constraints as well as the SST and δ13Cphytane-records from Site 1260, we subsequently reconstructed pCO2 levels across the OAE-2 interval. Accordingly, pCO2 decreased from ca. 1750 to 900 ppm during OAE-2, consistent with enhanced organic matter burial resulting in lowering pCO2. Whereas the onset of OAE-2 coincided with increased pCO2, in line with a volcanic trigger for this event, the observed cooling within OAE-2 probably resulted from CO2 sequestration in black shales outcompeting CO2 input into the atmosphere. Together these results show that the ice-free Cretaceous world was sensitive to changes in pCO2 related to perturbations of the global carbon cycle.

  12. Stable carbon and oxygen isotope stratigraphic evidence of Shuram Excursion and PC-C boundary in Bilara carbonate sequence of Rajasthan

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    Ansari, Arif; Pandey, Santosh; Sharma, Mukund; Agarwal, Shailesh; Kumar, Yogesh

    2017-04-01

    The Post-Cryogenian period was a time of sharp increase in ocean primary productivity and subsequent oxygenation to present atmospheric level (PAL), due to the massive influx of terrestrial weathering-derived nutrients in the sea. This change along with palaeogeography of continents during Late Ediacaran period instigated large scale deposition of carbonates with highly negative δ13C-carb. Like the continents those have established Shuram Excursion sites (i.e. Oman, Australia, China, North America), the location of Indian continent was also near atmospheric convergence zone (i.e. near the equator). Therefore a robust high-resolution carbon and oxygen stable isotope study was undertaken on Bilara carbonate sequences to test the possibility of Shuram Excursion and trace the Precambrian-Cambrian Boundary by comparing with well-dated established Shuram Excursion sites. The δ13C-carb and δ18O-carb in Bilara Group varies from -9.0 to 4.1 ‰ and from -10.7 to 8.3 ‰ respectively. Overall, most of the samples have δ18O-carb significantly above -10‰ below which carbonates are considered diagenetically altered. The δ13C-carb pattern is more similar to Yangtze Gorges platform where Ediacaran δ13C-carb variation profile has been divided into four negative (EN1, EN2, EN3, EN4) and three positive excursions (EP1, EP2, EP3). Similarities of δ13C-carb pattern demonstrate that Bilara is equivalent to Yangtze Gorges platform and, to some extent Shuram Formation. According to these comparisons, the Precambrian-Cambrian boundary lies near the top of Bilara Group.

  13. Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: pCO2 and paleoproductivity

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    van Bentum, E.C.; Reichart, G.-J.; Forster, A.; Sinninghe Damsté, J.S.

    2011-01-01

    A complete, well-preserved record of the Cenomanian/Turonian (C/T) Oceanic Anoxic Event 2 (OAE-2) was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260). Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane

  14. 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

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    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

  15. Calcium isotope constraints on the marine carbon cycle and CaCO3 deposition during the late Silurian (Ludfordian) positive δ13C excursion

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    Farkaš, Juraj; Frýda, Jiří; Holmden, Chris

    2016-10-01

    This study investigates calcium isotope variations (δ 44 / 40 Ca) in late Silurian marine carbonates deposited in the Prague Basin (Czech Republic), which records one of the largest positive carbon isotope excursion (CIE) of the entire Phanerozoic, the mid-Ludfordian CIE, which is associated with major climatic changes (abrupt cooling) and global sea-level fluctuations. Our results show that during the onset of the CIE, when δ13 C increases rapidly from ∼0‰ to ∼8.5‰, δ 44 / 40Ca remains constant at about 0.3 ± 0.1 ‰ (relative to NIST 915a), while 87Sr/86Sr in well-preserved carbonates are consistent with a typical Ludfordian seawater composition (ranging from ∼0.70865 to ∼0.70875). Such decoupling between δ13 C and δ 44 / 40Ca trends during the onset of the CIE is consistent with the expected order-of-magnitude difference in the residence times of Ca (∼106yr) and C (∼105yr) in the open ocean, suggesting that the mid-Ludfordian CIE was caused by processes where the biogeochemical pathways of C and Ca in seawater were mechanistically decoupled. These processes may include: (i) near shore methanogenesis and photosynthesis, (ii) changes in oceanic circulation and stratification, and/or (iii) increased production and burial of organic C in the global ocean. The latter, however, is unlikely due to the lack of geological evidence for enhanced organic C burial, and also because of unrealistic parameterization of the ocean C cycle needed to generate the observed CIE over the relatively short time interval. In contrast, higher up in the section where δ13 C shifts back to pre-excursion baseline values, there is a correlated shift to higher δ 44 / 40Ca values. Such coupling of the records of Ca and C isotope changes in this part of the study section is inconsistent with the abovementioned differences in oceanic Ca and C residence times, indicating that the record of δ 44 / 40Ca changes does not faithfully reflect the evolution of the oceanic Ca

  16. Furongian Stable Carbon Isotope Excursions (SPICE and HERB) in the Mixed Carbonate-Siliclastics on an Epeiric Platform of the Taebaeksan Basin, Korea

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    Chung, G. S.; Lim, J. N.; Park, T. Y.; Lee, K. S.; Lee, B. S.; Seo, K. S.

    2014-12-01

    Stable carbon isotope stratigraphy of the Late Cambrian mixed carbonate-siliciclastics from an epeiric platform allows a good stratigraphic marker and interpretation of paleoenvironmental conditions. The SPICE (Steptoean positive carbon excursion) and HERB (Hellnmaria-Red Tops Boundary) events are distinctly developed in the Furongian (Late Cambrian) of mixed carbonate-siliciclastics (Sesong and Hwajeol Formations) deposited on an epeiric platform of the Taebaeksan Basin, Korea, part of the North China Platform. The SPICE event occurs in the Prochuangia mansuyi zone and in the lower part of Chuangia zone of trilobite in the Sesong Formation with the δ13C values ranging from 1.1 to 1.8‰; it occurs in the stratigraphic interval mostly composed of nodular shale, massive to laminated fine sandstone with intercalation of limestone conglomerate beds which is interpreted to have been deposited in the inner to middle ramp. The HERB event begins at about the Eoconodontus notchpeakensis FAD of conodont and ends in the lower part of the range of E. notchpeakensis in the Hwajeol Formation. The HERB event shows negative δ13C values up to -5.5‰ forming a conspicuous and distinctive peak. The HERB event occurs in the stratigraphic interval mostly composed of nodular shale, limestone-shale couplet, and limestone conglomerate which is interpreted to have been deposited in the middle ramp. The onset of HERB event at the E. notchpeakensis FAD in the Taebaeksan basin, Korea suggests that the HERB event may be an excellent tool for intercontinental correlation defining the base of the terminal Cambrian (Stage 10). The paleoenvironmental conditions of the SPICE and HERB events seem to be contrary to each other; the SPICE event may be caused by the high rate of primary production and the high rate burial of organic matter with probable association of the high rate of input of terrigenous sediments. In contrast, the HERB event may be caused by the low rate of primary productivity

  17. Sedimentology of SPICE (Steptoean positive carbon isotope excursion): A high-resolution trace fossil and microfabric analysis of the middle to late Cambrian Alum Shale Formation, southern Sweden

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    Egenhoff, Sven; Fishman, Neil; Ahlberg, Per; Maletz, Jorg; Jackson, Allison; Kolte, Ketki; Lowers, Heather; Mackie, James; Newby, Warren; Petrowsky, Matthew

    2015-01-01

    The Cambrian Alum Shale Formation in the Andrarum-3 core from Scania, southern Sweden, consists of black siliciclastic mudstone with minor carbonate intercalations. Four facies comprise three siliciclastic mudstones and one fine-grained carbonate. The facies reflect deposition along a transect from deep ramp to basin on a Cambrian shelf. The three mudstone facies contain abundant clay clasts and laterally variable siltstone laminae. Bed-load transport processes seem to have dominated deposition on this deep shelf. These sedimentary rocks record mainly event deposition, and only relatively few, thin laminae probably resulted from suspension settling. The Alum Shale Formation deep shelf did not show a bioturbation gradient, but fecal strings are common and Planolites burrows are rare in all mudstone facies. Evidence for biotic colonization indicates that this mudstone environment was not persistently anoxic, but rather was most likely intermittently dysoxic. The Alum Shale Formation in the Andrarum-3 core shows an overall decrease of grain size, preserved energy indicators, and carbonate content upsection interpreted to reflect a deepening upward. The succession can also be divided into four small-scale fining-upward cycles that represent deepening, and four overlying coarsening-upward cycles that represent upward shallowing.

  18. ODP Site 1063 (Bermuda Rise) revisited: Oxygen isotopes, excursions and paleointensity in the Brunhes Chron

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    Channell, J. E. T.; Hodell, D. A.; Curtis, J. H.

    2012-02-01

    An age model for the Brunhes Chron of Ocean Drilling Program (ODP) Site 1063 (Bermuda Rise) is constructed by tandem correlation of oxygen isotope and relative paleointensity data to calibrated reference templates. Four intervals in the Brunhes Chron where paleomagnetic inclinations are negative for both u-channel samples and discrete samples are correlated to the following magnetic excursions with Site 1063 ages in brackets: Laschamp (41 ka), Blake (116 ka), Iceland Basin (190 ka), Pringle Falls (239 ka). These ages are consistent with current age estimates for three of these excursions, but not for "Pringle Falls" which has an apparent age older than a recently published estimate by ˜28 kyr. For each of these excursions (termed Category 1 excursions), virtual geomagnetic poles (VGPs) reach high southerly latitudes implying paired polarity reversals of the Earth's main dipole field, that apparently occurred in a brief time span (<2 kyr in each case), several times shorter than the apparent duration of regular polarity transitions. In addition, several intervals of low paleomagnetic inclination (low and negative in one case) are observed both in u-channel and discrete samples at ˜318 ka (MIS 9), ˜412 ka (MIS 11) and in the 500-600 ka interval (MIS 14-15). These "Category 2" excursions may constitute inadequately recorded (Category 1) excursions, or high amplitude secular variation.

  19. Stable carbon and oxygen isotope study on benthic foraminifera ...

    Indian Academy of Sciences (India)

    Isotopic fractionations are mainly controlled by ontogeny, bottom/pore water chemistry, habitat preference, kinetic effect and respiration. ... Infaunal species (B. marginata, Ammonia spp. and N. auris) show a lighter carbon isotopic excursion with respect to the epifaunal to shallow infaunal forms (C. wuellerstorfi, ...

  20. Sinemurian–Pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the Paris Basin

    DEFF Research Database (Denmark)

    Peti, Leonie; Thibault, Nicolas Rudolph; Clemence, Marie-Emilie

    2017-01-01

    organic carbon isotope curve based on 385 data points. The main bioevents, i.e. the first occurrences of Parhabdolithus liasicus, Crepidolithus pliensbachensis, Crepidolithus crassus, Mitrolithus lenticularis, Similiscutum cruciulus sensu lato, Lotharingius hauffii, Crepidolithus cavus and Lotharingius...... carbon isotope excursions are identified and defined in the Paris Basin including the well-documented Sinemurian–Pliensbachian boundary event. One positive excursion is further defined in the Pliensbachian interval. Our calibration of high-resolution calcareous nannofossil biostratigraphy to ammonite...... biostratigraphy and organic carbon isotopes represents a new stratigraphic reference for the Lower Jurassic series....

  1. 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...... analyses. The carbon isotope record of diagenetically unaltered samples from the Carnic Alps (Austria) and Karavanke Mountains (Slovenia) shows generally high δ13C values, but Late Carboniferous and Early Permian successions are affected by a diagenetic alteration as consequence of glacio-eustatic sea level changes...... published, is not obvious and negative excursions related to changes in the carbon isotope composition of the global oceanic carbon pool cannot be confirmed, except for the Permian–Triassic boundary interval....

  2. The Valanginian terrestrial carbon-isotope record

    Science.gov (United States)

    Grocke, D. R.; Price, G. D.; Baraboshkin, E.; Mutterlose, J.; Ruffell, A. H.

    2003-04-01

    A stratigraphic, biostratigraphic and isotopic investigation has been performed on a Crimean section located on the Kacha River, Verkhorechie Village, SW Crimea. This clastic-dominated succession consists of a series of bioturbated inter-bedded shallow-marine silty sands, claystones and some oolitic sands. A published detailed study of the ammonite fauna has been undertaken and has revealed that the succession can be compared to standard Tethyan schemes. The lower part of the succession is dated on the basis of the ammonite fauna as Early Valanginian (otopeta-campylotoxus ammonite Zones), although this latter zone is highly condensed. A more expanded Late Valanginian is present (verrucosum, callidiscus and tauricum ammonite Zones), and is overlain by sand-dominated sediments of Early Hauterivian age. Throughout this section woody plant matter ranging in preservation from charcoal to coal has been collected and analyzed for stable carbon-isotope ratios. There is no correlation between state of preservation and carbon-isotope ratios. Carbon-isotope ratios range in the Early Valanginian from -24 ppm to -22 ppm, and in the mid-verrucosum Zone values shift abruptly towards more positive values and peak at -18 ppm in the lower callidiscus Zone. Wood carbon-isotope ratios decrease gradually through the remainder of the callidiscus Zone and return to pre-excursion values in the tauricum Zone. The remaining Hauterivian values fluctuate between -24 ppm to -21 ppm. The structure, magnitude and timing of the terrestrial carbon-isotope curve is very similar to the marine carbonate curve (from +1 ppm to +3 ppm) for the Valanginian. This would indicate, based on a delta-delta relationship between organic matter and carbonate, that there was very little change in atmospheric CO_2 concentrations during the Valanginian, and that the isotopic composition of the global carbon reservoir shifted. Future research on an Early Cretaceous (Valanginian-Hauterivian) interval from the Yatria

  3. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    retain an isotopically light Cr signature. Cr(VI) enriched in heavy Cr isotopes is then transported via river waters to the oceans and sequestered into marine sediments. Marine chemical sediments such asbanded iron formations and modern marine carbonates have proven useful in recording the Cr isotope...... with calcium carbonate in order to test the reliability of the Cr carbonate compositions. Several experimental approaches have been employed to elucidate the fractionation behavior of Cr isotopes when Cr(VI) is incorporated into calcium carbonate phases. These results indicate that at lower Cr concentrations......Chromium (Cr) is a redox sensitive element potentially capable of tracing fine-scale fluctuations of the oxygenation of Earth’s early surface environments and seawater. The Cr isotope composition of carbonates could perhaps be used as paleo-redox proxy to elucidate changes in the geological past...

  4. 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.

  5. Carbon isotopes and lipid biomarkers from organic-rich facies of the Shuram Formation, Sultanate of Oman.

    Science.gov (United States)

    Lee, C; Fike, D A; Love, G D; Sessions, A L; Grotzinger, J P; Summons, R E; Fischer, W W

    2013-09-01

    The largest recorded carbon isotopic excursion in Earth history is observed globally in carbonate rocks of middle Ediacaran age. Known from the Sultanate of Oman as the 'Shuram excursion', this event records a dramatic, systematic shift in δ(13) Ccarbonate values to ca. -12‰. Attempts to explain the nature, magnitude and origin of this excursion include (i) a primary signal resulting from the protracted oxidation of a large dissolved organic carbon reservoir in seawater, release of methane from sediment-hosted clathrates, or water column stratification; and (ii) a secondary signal from diagenetic processes. The compositions and isotope ratios of organic carbon phases during the excursion are critical to evaluating these ideas; however, previous work has focused on localities that are low in organic carbon, hindering straightforward interpretation of the observed time-series trends. We report carbon isotope data from bulk organic carbon, extracted bitumen and kerogen, in addition to lipid biomarker data, from a subsurface well drilled on the eastern flank of the South Oman Salt Basin, Sultanate of Oman. This section captures Nafun Group strata through the Ediacaran-Cambrian boundary in the Ara Group and includes an organic-rich, deeper-water facies of the Shuram Formation. Despite the high organic matter contents, the carbon isotopic compositions of carbonates - which record a negative δ(13) C isotope excursion similar in shape and magnitude to sections elsewhere in Oman - do not covary with those of organic phases (bulk TOC, bitumen and kerogen). Paired inorganic and organic δ(13) C data only display coupled behaviour during the latter part of the excursion's recovery. Furthermore, lipid biomarker data reveal that organic matter composition and source inputs varied stratigraphically, reflecting biological community shifts in non-migrated, syngenetic organic matter deposited during this interval. © 2013 John Wiley & Sons Ltd.

  6. Final Technical Report: Fundamental Research on the Fractionation of Carbon Isotopes during Photosynthesis, New Interpretations of Terrestrial Organic Carbon within Geologic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Brian [Univ. of Louisiana, Lafayette (United States); Jahren, A. Hope [Univ. of Louisiana, Lafayette (United States)

    2017-11-30

    The goal for the current grant period (2013 – 2016) was to quantify the effect of changing atmospheric carbon dioxide concentration (pCO2) on published terrestrial carbon isotope excursion events. This work supported four scientists across multiple career stages, and resulted in 5 published papers.

  7. Final Report: Fundamental Research on the Fractionation of Carbon Isotopes during Photosynthesis, New Interpretations of Terrestrial Organic Carbon within Geologic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jahren, A. Hope [Univ. of Hawaii, Honolulu, HI (United States); Schubert, Brian A. [Univ. of Louisiana, Lafayette, LA (United States)

    2017-08-02

    The goal for the current grant period (2013 – 2016) was to quantify the effect of changing atmospheric carbon dioxide concentration (pCO2) on published terrestrial carbon isotope excursion events. This work supported four scientists across multiple career stages, and resulted in 5 published papers.

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

    Science.gov (United States)

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

    2017-07-01

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

  9. The Iceland Basin excursion: Age, duration, and excursion field geometry

    Science.gov (United States)

    Channell, J. E. T.

    2014-12-01

    The Iceland Basin geomagnetic excursion coincided with the marine isotope stage (MIS) 6/7 boundary. The age and duration of the excursion, at seven North Atlantic sites with sufficient isotope data, are estimated by matching marine isotope stage (MIS) 7a-7c to a calibrated template. Two criteria for defining the excursion, virtual geomagnetic pole (VGP) latitudes Earth's main axial dipole reversed polarity during the excursion, if only for ˜1 kyr; implying that excursions can be manifested globally and are important in millennial-scale stratigraphy. VGP clustering in the South Atlantic and NW Pacific roughly coincide with maxima in the vertical-downward component of the modern nondipole (ND) field determined at the Earth's surface, which implies that the ND field became dominant as the geocentric dipole field weakened during the excursion, and also that the ND field configuration is long-lived on multimillennial timescales.

  10. Boron and calcium isotope composition in Neoproterozoic carbonate rocks from Namibia: evidence for extreme environmental change

    Science.gov (United States)

    Kasemann, Simone A.; Hawkesworth, Chris J.; Prave, Anthony R.; Fallick, Anthony E.; Pearson, Paul N.

    2005-02-01

    The level and evolution of atmospheric carbon dioxide throughout Earth's history are key issues for palaeoclimate reconstructions, especially during times of extreme climate change such as those that marked the Neoproterozoic. The carbon isotope ratios of marine carbonates are crucial in the correlation and identification of Neoproterozoic glacial deposits, and they are also used as a record for biogeochemical cycling and potential proxy for atmospheric pCO 2. Likewise, the boron and calcium isotope compositions of marine carbonates are potential proxies for palaeo-seawater pH and the ratio of calcium fluxes into and out of seawater, respectively, and together they may be used to estimate atmospheric carbon dioxide. Here we use B and Ca isotopes to estimate palaeoenvironmental conditions in the aftermath of a major Neoproterozoic glaciation in Namibia. The validity of the B and Ca isotope variation in the ancient marine carbonates is evaluated using the oxygen isotope composition of the carbonates and its correlation to the carbon isotope variation. A negative (2.7 to -6.2‰) δ 11B excursion occurs in the postglacial carbonates and is interpreted to reflect a temporary decrease in seawater pH. Associated variations in δ 44Ca values (ranging between 0.35 and 1.14‰) are linearly coupled with the carbon isotope ratios and imply enhanced postglacial weathering rates. The reconstructed seawater pH and weathering profiles indicates that high atmospheric CO 2 concentrations were likely during the melt back of Neoproterozoic glaciations and precipitation of cap carbonates. However, the B isotope trend suggests that these concentrations rapidly ameliorated and they do not co-vary with δ 13C. Thus models attempting to link long-lived negative δ 13C excursions to elevated pCO 2 need to be reconsidered.

  11. A carbon isotopic and sedimentological record of the latest Devonian (Famennian) from the Western U.S. and Germany

    Science.gov (United States)

    Myrow, P.M.; Strauss, J.V.; Creveling, J.R.; Sicard, K.R.; Ripperdan, R.; Sandberg, C.A.; Hartenfels, S.

    2011-01-01

    New carbon isotopic data from upper Famennian deposits in the western United States reveal two previously unrecognized major positive isotopic excursions. The first is an abrupt ~. 3??? positive excursion, herein referred to as ALFIE (A Late Famennian Isotopic Excursion), recorded in two sections of the Pinyon Peak Limestone of north-central Utah. Integration of detailed chemostratigraphic and biostratigraphic data suggests that ALFIE is the Laurentian record of the Dasberg Event, which has been linked to transgression in Europe and Morocco. Sedimentological data from the Chaffee Group of western Colorado also record transgression at a similar biostratigraphic position, with a shift from restricted to open-marine lithofacies. ALFIE is not evident in chemostratigraphic data from age-equivalent strata in Germany studied herein and in southern Europe, either because it is a uniquely North American phenomenon, or because the German sections are too condensed relative to those in Laurentia. A second positive carbon isotopic excursion from the upper Chaffee Group of Colorado is recorded in transgressive strata deposited directly above a previously unrecognized paleokarst interval. The age of this excursion, and the duration of the associated paleokarst hiatus, are not well constrained, although the events occurred sometime after the Late Famennian Middle expansa Zone. The high positive values recorded in this excursion are consistent with those associated with the youngest Famennian Middle to Late praesulcata Hangenberg Isotopic Excursion in Europe, the isotopic expression of the Hangenberg Event, which included mass extinction, widespread black shale deposition, and a glacio-eustatic fall and rise. If correct, this would considerably revise the age of the Upper Chaffee Group strata of western Colorado. ?? 2011 Elsevier B.V.

  12. 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.

  13. Dual Carbon and Nitrogen Isotope Analysis

    African Journals Online (AJOL)

    According to Hemminga & Mateo. (1996), values of carbon and nitrogen isotope ratios vary considerably between seagrass species. It might also be expected that the remaining seagrass species could have some influence on the shrimp carbon signal. Isotopic evidence for mangroves being a carbon source for shrimps ...

  14. Robust optical carbon dioxide isotope analyzer Project

    Data.gov (United States)

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

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

    Science.gov (United States)

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

    2016-12-01

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

  16. The Importance of Sulfur on Enriched Carbon Isotopes and Extreme Carbon Cycle Perturbations of the Cryogenian

    Science.gov (United States)

    Gouldey, J. C.; Hurtgen, M. T.; Halverson, G. P.

    2012-12-01

    The Neoproterozoic carbon isotope record is unusual in that it is characterized by high δ13Ccarbonate values that persist for tens of millions of years and that are interrupted by large negative excursions that coincide with two global-scale glaciations: the Sturtian (~710 Ma) and the Marinoan (~635 Ma). While the mechanisms underpinning the negative carbon isotope excursions remain controversial, the prolonged intervals of 13C-enrichment have been attributed to increased primary production and organic carbon burial. Here, we present sulfur isotope data (sulfate and pyrite) from carbonate rocks deposited in northern Namibia spanning the interglacial interval (Cryogenian Period) in order to test the hypothesis that changes in marine sulfate concentrations impacted phosphorus recycling efficiency and played a role in regulating the Neoproterozoic carbon cycle. δ34Spyrite results through the interglacial interval are 34S-enriched (-5.65‰ to 39.17‰). These data suggest sulfate concentrations were very low during this time interval as a result of nearly complete reduction of sulfate via microbes (microbial sulfate reduction) while the major fluxes of sulfate into the ocean (riverine input) were restricted due to a reduction of the hydrologic cycle during glaciation. Importantly, positive swings in δ13Ccarbonate are accompanied by negative δ34Spyrite shifts. We interpret these negative δ34Spyrite shifts as intervals of increasing sulfate concentration. As sulfate concentrations rise, bacterial sulfate reduction results in more sulfide production, which then reacts with various iron phases to from pyrite. A major sink for phosphorus in the ocean is adsorption onto iron oxides and oxyhydroxides. Therefore, the consumption of iron oxides and oxyhydroxides during pyrite formation allows for more phosphorus to be recycled in marine waters, stimulating primary production.

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

    Science.gov (United States)

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

    2014-05-01

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

  18. Carbon isotope signatures of latest Permian marine successions of the Southern Alps suggest a continental runoff pulse enriched in land plant material

    Directory of Open Access Journals (Sweden)

    S. H. Kraus

    2013-02-01

    Full Text Available The latest Permian mass extinction, the most severe Phanerozoic biotic crisis, is marked by dramatic changes in palaeoenvironments. These changes significantly disrupted the global carbon cycle, reflected by a prominent and well known negative carbon isotope excursion recorded in marine and continental sediments. Carbon isotope trends of bulk carbonate and bulk organic matter in marine deposits of the European Southern Alps near the low-latitude marine event horizon deviate from each other. A positive excursion of several permil in δ13Corg starts earlier and is much more pronounced than the short-term positive 13Ccarb excursion; both excursions interrupt the general negative trend. Throughout the entire period investigated, 13Corg values become lighter with increasing distance from the palaeocoastline. Changing 13Corg values may be due to the influx of comparatively isotopically heavy land plant material. The stronger influence of land plant material on the 13Corg during the positive isotope excursion indicates a temporarily enhanced continental runoff that may either reflect increased precipitation, possibly triggered by aerosols originating from Siberian Trap volcanism, or indicate higher erosion rate in the face of reduced land vegetation cover. doi:10.1002/mmng.201300004

  19. High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle

    Science.gov (United States)

    Them, T. R.; Gill, B. C.; Caruthers, A. H.; Gröcke, D. R.; Tulsky, E. T.; Martindale, R. C.; Poulton, T. P.; Smith, P. L.

    2017-02-01

    The Mesozoic Era experienced several instances of abrupt environmental change that are associated with instabilities in the climate, reorganizations of the global carbon cycle, and elevated extinction rates. Often during these perturbations, oxygen-deficient conditions developed in the oceans resulting in the widespread deposition of organic-rich sediments - these events are referred to as Oceanic Anoxic Events or OAEs. Such events have been linked to massive injections of greenhouse gases into the ocean-atmosphere system by transient episodes of voluminous volcanism and the destabilization of methane clathrates within marine environments. Nevertheless, uncertainty surrounds the specific environmental drivers and feedbacks that occurred during the OAEs that caused perturbations in the carbon cycle; this is particularly true of the Early Jurassic Toarcian OAE (∼183.1 Ma). Here, we present biostratigraphically constrained carbon isotope data from western North America (Alberta and British Columbia, Canada) to better assess the global extent of the carbon cycle perturbations. We identify the large negative carbon isotope excursion associated with the OAE along with high-frequency oscillations and steps within the onset of this excursion. We propose that these high-frequency carbon isotope excursions reflect changes to the global carbon cycle and also that they are related to the production and release of greenhouse gases from terrestrial environments on astronomical timescales. Furthermore, increased terrestrial methanogenesis should be considered an important climatic feedback during Ocean Anoxic Events and other similar events in Earth history after the proliferation of land plants.

  20. Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end-Triassic mass extinction

    Science.gov (United States)

    Bartolini, A.; Guex, J.; Spangenberg, J. E.; Schoene, B.; Taylor, D. G.; Schaltegger, U.; Atudorei, V.

    2012-01-01

    This study provides an organic carbon stable isotope (δ13Corg) record calibrated with detailed ammonite biostratigraphy, following the end-Triassic biological crisis. Precise correlation between this crucial fossil group and the δ13Corg record is key to understanding feedbacks between biological and environmental events following mass extinction. The latest Triassic and Hettangian δ13Corg record shows several negative and positive excursions. The end-Triassic negative shift coinciding with the mass extinction interval is followed by a positive excursion in the earliest Hettangian Psiloceras spelae beds, which marks the onset of recovery in the marine ecosystem. This positive trend is interrupted by a second negative δ13Corg excursion in the P. pacificum beds related to a minor ammonite extinction event. This pattern of the δ13Corg curve culminates in the uppermost Hettangian Angulata Zone major positive excursion. This indicates that both the ecosystem and the carbon cycle remained in a state of perturbation for at least 2 Ma, although the recovery of some pelagic taxa already began at the base of Jurassic. The early and late Hettangian positive δ13Corg excursions have been confused in several recent papers. Here, we show that during the Hettangian there are indeed two distinct positive δ13Corg excursions. Phases of anoxia and further pulses of Central Atlantic Magmatic Province volcanism during the Hettangian might have inhibited the full recovery for that interval of time. The main Liasicus-Angulata organic positive CIE (carbon isotope excursion) during the Late Hettangian might be related to gradual decreasing of pCO2 due to protracted high organic burial, and coincides with a second phase of recovery, as indicated by a pulse of ammonoid diversification.

  1. Preliminary Earth System Modeling (cGENIE) of Paired Organic and Inorganic Carbon Isotope Records to Investigate Carbon Cycle Behavior During the Triassic-Jurassic Transition

    Science.gov (United States)

    Yager, J. A.; Stellmann, J. L.; West, A. J.; Corsetti, F. A.; Berelson, W.; Bottjer, D. J.; Rosas, S.

    2016-12-01

    The stable C isotope composition of marine carbonate and organic C yields information regarding major changes in global carbon cycling over geologic time. Excursions from baseline C isotope compositions during the Late Triassic and early Jurassic coincide with the end-Triassic mass extinction. Much remains to be understood about the global extent of these excursions, and about their causes. Here, we use observations from a record from Northern Peru (Levanto) to generate hypotheses concerning C cycle changes, focusing on comparison to other sections spanning the Triassic-Jurassic boundary. Our observations include a decoupling between organic and inorganic C isotopes in some records, broad similarities in the pattern of excursions between sections, and a potential offset between the major ocean basins (Tethys and Panthalassa) in both inorganic and organic C isotope records. We are currently adapting a spatially resolved Earth System Model (cGENIE) for this time period with the goal of using this model to explore possible mechanistic causes of these observations, aiming to tie the C isotope records to changes in global carbon cycle dynamics at the time.

  2. Oxygen isotope fractionation in double carbonates.

    Science.gov (United States)

    Zheng, Yong-Fei; Böttcher, Michael E

    2016-01-01

    Oxygen isotope fractionations in double carbonates of different crystal structures were calculated by the increment method. Synthesis experiments were performed at 60 °C and 100 °C to determine oxygen and carbon isotope fractionations involving PbMg[CO3]2. The calculations suggest that the double carbonates of calcite structure are systematically enriched in (18)O relative to those of aragonite and mixture structures. Internally consistent oxygen isotope fractionation factors are obtained for these minerals with respect to quartz, calcite and water at a temperature range of 0-1200 °C. The calculated fractionation factors for double carbonate-water systems are generally consistent with the data available from laboratory experiments. The experimentally determined fractionation factors for PbMg[CO3]2, BaMg[CO3]2 and CaMg[CO3]2 against H2O not only fall between fractionation factors involving pure carbonate end-members but are also close to the calculated fractionation factors. In contrast, experimentally determined carbon isotope fractionation factors between PbMg[CO3]2 and CO2 are much closer to theoretical predictions for the cerussite-CO2 system than for the magnesite-CO2 system, similar to the fractionation behavior for BaMg[CO3]2. Therefore, the combined theoretical and experimental results provide insights into the effects of crystal structure and exchange kinetics on oxygen isotope partitioning in double carbonates.

  3. 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...

  4. The succession of Hirnantian events based on data from Baltica: brachiopods, chitinozoans, conodonts, and carbon isotopes

    Directory of Open Access Journals (Sweden)

    Kaljo, Dimitri

    2008-12-01

    Full Text Available The Hirnantian (late Ordovician environment was complex and dynamic. Understanding the correct order of events and their precise correlation with a time scale are extremely important for the development of different kinds of environmental interpretations. The lower boundary of the Hirnantian Stage is officially defined by “the lowest occurrence of Normalograptus extraordinarius, the base of major positive carbon-13 isotope excursion, and the beginning of a pronounced sea-level fall associated with onset of a major glaciation” (ICS website. Our aim is to check if these events are synchronous, particularly how the situation is with respect to the Baltic. Thus several sections were analysed using mainly East Baltic data (drill cores, but also data from elsewhere, including brachiopod, chitinozoan, and conodont biostratigraphy combined with graptolite and carbon isotope data. Brachiopod faunas of the Pirgu and Porkuni stages are rather similar to those of the Ellis Bay Formation of Anticosti Island, Quebec, but the Pirgu assemblage, as well as that of the lower Ellis Bay Fm. lack key elements of the Hirnantian faunas. The primary criterion quoted above is stable, but auxiliary data like the isotope curve are less convincing. When the latter is used, it should be specified, e.g. that the carbon isotope excursion begins usually slightly earlier (in the Diceratograptus mirus Biozone, but it might be conventionally placed into the N. extraordinarius Biozone when a biostratigraphical proxy is available. The peak of the excursion is in the lower N. persculptus Biozone, but the main increase in values takes place in the N. extraordinarius Biozone. The Spinachitina taugourdeaui Biozone marks at many localities the bottom of the Hirnantian, and only the recent chitinozoan–graptolite data from the topmost Lousy Cove Member (on Anticosti Island suggest a mid-Hirnantian age, which is at variance with common correlation schemes.

  5. Carbon Isotopes in an Earth System Model

    Science.gov (United States)

    Cuntz, M.; Reick, C. H.; Maier-Reimer, E.; Heimann, M.; Scholze, M.; Naegler, T.

    2009-04-01

    We present first calculations of the carbon isotopic composition of carbon dioxide in the Earth System Model (ESM) COSMOS. Earth System models consist of coupled models of the ocean, the atmosphere, the land surface, the biosphere (marine and terrestrial, plants and soils), and the cryosphere (snow and ice). In COSMOS from the Max Planck Institute for Meteorology, Hamburg, Germany, these components are the model of the atmospheric circulation ECHAM, the physical ocean model MPI-OM, the land surface parameterisation JSBACH and the oceanic carbon cycle model HAMOCC. The ESM COSMOS therefore calculates its own climate and CO2 concentrations during the diel course with a few degrees resolution, driven only by solar activity and human perturbations. The new model version now computes the multiple fractionation processes occurring during uptake of CO2 from the atmosphere by the terrestrial and marine biosphere. The model then redistributes the isotopic compositions in the land and ocean biospheres, including respiration, phenology, fire, land-use change and carbon export. This means that it includes a full isotopic carbon cycle, in the atmosphere, the ocean and on land. The model calculates not only the stable carbon isotope signatures but also radiocarbon activities in the Earth System. It will include in future the radiocarbon perturbation due to nuclear bomb tests. We compare first results of the ESM with other global estimates of terrestrial discrimination. We also compare predicted zonal and seasonal variations of isotope ratios in atmospheric CO2 with measurements from the GLOBALVIEW flask network. The stable and radioactive carbon isotopes are excellent tests for the overall model performance but also for individual model components. For example radiocarbon will be used to test stratosphere-troposphere exchange, ocean circulation and air-sea gas exchange. The isotope-enabled model can be used in future for example to predict carbon isotope ratios of terrestrial

  6. Site-Specific Carbon Isotopes in Organics

    Science.gov (United States)

    Piasecki, A.; Eiler, J. M.

    2012-12-01

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

  7. Does the Shuram δ13C excursion record Ediacaran oxygenation?

    Science.gov (United States)

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

    2013-12-01

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

  8. Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

    Directory of Open Access Journals (Sweden)

    M. Schobben

    2017-11-01

    Full Text Available Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian–Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the

  9. Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

    Science.gov (United States)

    Schobben, Martin; van de Velde, Sebastiaan; Gliwa, Jana; Leda, Lucyna; Korn, Dieter; Struck, Ulrich; Vinzenz Ullmann, Clemens; Hairapetian, Vachik; Ghaderi, Abbas; Korte, Christoph; Newton, Robert J.; Poulton, Simon W.; Wignall, Paul B.

    2017-11-01

    Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian-Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-)sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the observed signal of carbon

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

    Science.gov (United States)

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

    1983-01-01

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

  11. Carbon and oxygen isotope compositions of the carbonate facies in ...

    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 ...

  12. Carbon isotopes of graphite: Implications on fluid history

    OpenAIRE

    F.J. Luque; E. Crespo-Feo; J.F. Barrenechea; L. Ortega

    2012-01-01

    Stable carbon isotope geochemistry provides important information for the recognition of fundamental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elaboration of models for the global carbon cycle. Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon (organic matter, mantle, or carbonates) and help to constrain the fluid history and the mechanisms involved in graphite deposition. Gr...

  13. Stable carbon isotope analysis of coprocessing materials

    Energy Technology Data Exchange (ETDEWEB)

    Burke, F. P.; Winschel, R. A.; Lancet, M. S.

    1989-06-01

    The program is designed to address a substantial, demonstrated need of the coprocessing community (both exploratory and development) for a technique to quantitatively distinguish the contributions of the individual coprocessing feedstocks to the various products. The carbon isotope technique is currently in routine use for other applications. Results achieved this quarter include: Feed and product fractions from a Kentucky 9 coal/Kentucky tar sand bitumen coprocessing bench unit run at the Kentucky Center for Applied Energy Research (CAER) were analyzed for carbon isotope ratios. Corrections were made to the coal carbon recoveries and selectivities from the products of HRI Run 227-53. Feeds (Westerholt coal/Cold Lake VSB) and products from two periods of HRI coprocessing Run 238-1 were analyzed. Three petroleum samples and three coal samples were pyrolyzed at 800{degree}F for 30 min to determine the effect of pyrolysis on the isotopic homogeneity of each petroleum and coal sample. Products from each pyrolysis test were separated into five fractions; an additional set of coprocessing samples and a set of two-stage coal liquefaction samples were obtained from HRI for future work; work performed by the Pennsylvania State University show that microscopy is a promising method for distinguishing coal and petroleum products in residual coprocessing materials; and coal and petroleums that have large differences in carbon isotope ratios were identified for Auburn University. 7 refs., 2 figs., 12 tabs.

  14. Free Air Respiratory Carbon Isotope Enrichment Experiment

    Science.gov (United States)

    Sternberg, L. D.; Greaver, T.; Schaffer, B.; Moreno, T.

    2003-12-01

    Recycling of respiratory carbon in canopies is difficult to measure. Other than a steady state model, there are currently no direct methods of measuring recycling. Respiratory carbon recycling not only will affect the carbon isotope ratio signature of the canopy, but is also important in partitioning gross photosynthesis and respiration from net ecosystem exchange (NEE). In order to better understand recycling, we empirically derived an integrated measure of recycling in a cover crop (Crotalaria juncea L.) and compared it with that derived by the steady state model. A measured dose of nitrogen gas having CO2 with a high Carbon-13 abundance (41%) was applied at ground level ( ˜10 cm above the soil surface) with a system of hoses in a 10 by 10 m plot embedded in a 30 by 30 m plot. We adjusted the flux rate of this enriched gas weekly to correspond to weekly measurements of soil respiration rates. The gas application rates at ground level were sufficiently low so as to not affect the carbon dynamics of the treatment plot relative to that of a control plot with only nitrogen (no CO2) applied. The isotopic composition of the applied gas, however, was high enough to significantly increase the isotopic composition of respired CO2. Using the carbon isotopic composition of respiration and biomass from the control and treatment plots and mass balance principles we calculated that 45% of the total respired CO2 is recycled by this crop, which compares well with that derived by the steady state model (48%). Partitioning of gross photosynthesis and respiration by isotopic methods usually assumes no recycling. Recycling, however, will have an effect on the isotopic composition of respired CO2. After correcting for the recycling effects on the carbon isotope ratios of respired CO2 leaving the canopy, we calculated that the average gross photosynthesis for this crop was 40.4μ moles/m2s and gross respiration was in the order of 17.8 μ moles/m2s. These values are similar to those

  15. 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.

  16. Stable carbon and oxygen isotope study on benthic foraminifera: Implication for microhabitat preferences and interspecies correlation

    Science.gov (United States)

    Bhaumik, Ajoy K.; Kumar, Shiv; Ray, Shilpi; Vishwakarma, G. K.; Gupta, Anil K.; Kumar, Pushpendra; Sain, Kalachand

    2017-07-01

    Stable isotopes of benthic foraminifera have widely been applied in micropalaeontological research to understand vital effects in foraminifera. Isotopic fractionations are mainly controlled by ontogeny, bottom/pore water chemistry, habitat preference, kinetic effect and respiration. Discontinuous abundance of a species for isotopic analysis has forced us to select multiple species from down-core samples. Thus standardisation factors are required to convert isotopic values of one species with respect to other species. The present study is pursued on isotopic values of different pairs of benthic foraminifera from the Krishna-Godavari basin and Peru offshore to understand habitat-wise isotopic variation and estimation of isotopic correction factors for the paired species ( Cibicides wuellerstorfi-Bulimina marginata, Ammonia spp.- Loxostomum amygdalaeformis and Bolivina seminuda-Nonionella auris). Infaunal species ( B. marginata, Ammonia spp. and N. auris) show a lighter carbon isotopic excursion with respect to the epifaunal to shallow infaunal forms ( C. wuellerstorfi, L. amygdalaeformis and B. seminuda). These lighter δ^{13} C values are related to utilisation of CO2 produced by anaerobic remineralisation of organic matter. However, enrichment of δ^{18} O for the deeper microhabitat (bearing lower pH and decreased {CO3}^{2-}) is only recorded in case of B. marginata. It is reverse in case of N. auris and related to utilisation of respiratory CO2 and internal dissolve inorganic carbon pool. Estimation of interspecies isotopic correction factors for the species pairs (δ^{13} C of C. wuellerstorfi- B. marginata, L. amygdalaeformis- Ammonia spp., N. auris- B. seminuda) and δ^{18} O of C. wuellerstorfi- B. marginata are statistically reliable and may be used in palaeoecological studies.

  17. The end-Triassic negative δ13C excursion : A lithologic test

    NARCIS (Netherlands)

    Bachan, Aviv; van de Schootbrugge, Bas; Payne, Jonathan L.

    2014-01-01

    The end-Triassic mass extinction is associated with a large negative carbon isotope excursion, which has been interpreted as reflecting the rapid injection of 13C depleted CO2 or methane associated with the emplacement of the Central Atlantic Magmatic Province. However, in a number of sections in

  18. Aerosol carbon isotope composition over Baltic Sea

    Science.gov (United States)

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

    2017-04-01

    Particulate carbonaceous matter is significant contributor to ambient particulate matter originating from intervening sources which contribution is difficult to quantify due to source diversity, chemical complexity and processes during atmospheric transport. Carbon isotope analysis can be extremely useful in source apportionment of organic matter due to the unique isotopic signatures associated with anthropocentric (fossil fuel), continental (terrestrial plants) and marine sources, and is particularly effective when these sources are mixed (Ceburnis et al., 2011;Ceburnis et al., 2016). We will present the isotope ratio measurement results of aerosol collected during the cruise in the Baltic Sea. Sampling campaign of PM10 and size segregated aerosol particles was performed on the R/V "Oceania" in October 2015. Air mass back trajectories were prevailing both from the continental and marine areas during the sampling period. The total carbon concentration varied from 1 µg/m3 to 8 µg/m3. Two end members (δ13C = -25‰ and δ13C = -28 ‰ ) were established from the total stable carbon isotope analysis in PM10 fraction. δ13C analysis in size segregated aerosol particles revealed δ13C values being highest in the 1 - 2.5 µm range (δ13C = -24.9 ‰ ) during continental transport, while lowest TC δ13C values (δ13C ≈ -27 ‰ ) were detected in the size range D50 matter origin in submicron marine aerosol by 13 C and 14 C isotope analysis, Atmospheric Chemistry and Physics, 11, 8593-8606, 2011. Ceburnis, D., Masalaite, A., Ovadnevaite, J., Garbaras, A., Remeikis, V., Maenhaut, W., Claeys, M., Sciare, J., Baisnée, D., and O'Dowd, C. D.: Stable isotopes measurements reveal dual carbon pools contributing to organic matter enrichment in marine aerosol, Scientific Reports, 6, 2016. Masalaite, A., Remeikis, V., Garbaras, A., Dudoitis, V., Ulevicius, V., and Ceburnis, D.: Elucidating carbonaceous aerosol sources by the stable carbon δ13C TC ratio in size

  19. 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.

  20. Carbon isotope chemostratigraphy and precise dating of middle Frasnian (lower Upper Devonian) Alamo Breccia, Nevada, USA

    Science.gov (United States)

    Morrow, J.R.; Sandberg, C.A.; Malkowski, K.; Joachimski, M.M.

    2009-01-01

    At Hancock Summit West, Nevada, western USA, uppermost Givetian (upper Middle Devonian) and lower and middle Frasnian (lower Upper Devonian) rocks of the lower Guilmette Formation include, in stratigraphic sequence, carbonate-platform facies of the conodont falsiovalis, transitans, and punctata Zones; the type Alamo Breccia Member of the middle punctata Zone; and slope facies of the punctata and hassi Zones. The catastrophically deposited Alamo Breccia and related phenomena record the ~ 382??Ma Alamo event, produced by a km-scale bolide impact into a marine setting seaward of an extensive carbonate platform fringing western North America. Re-evaluation of conodonts from the lower Guilmette Formation and Alamo Breccia Member, together with regional sedimentologic and conodont biofacies comparisons, now firmly locates the onset of the Johnson et al. (1985) transgressive-regressive (T-R) cycle IIc, which occurred after the start of the punctata Zone, within a parautochthonous megablock low in the Alamo Breccia. Whole-rock carbon isotope analyses through the lower Guilmette Formation and Alamo Breccia Member reveal two positive ??13Ccarb excursions: (1) a small, 3??? excursion, which is possibly correlative with the falsiovalis Event previously identified from sections in Western Europe and Australia, occurs below the breccia in the Upper falsiovalis Zone to early part of the transitans Zone; and (2) a large, multi-part excursion, dominated by a 6??? positive shift, begins above the start of the punctata Zone and onset of T-R cycle IIc and continues above the Alamo Breccia, ending near the punctata- hassi zonal boundary. This large excursion correlates with the punctata Event, a major positive ??13C excursion previously recognized in eastern Laurussia and northern Gondwana. Consistent with previous studies, at Hancock Summit West the punctata Event is apparently not associated with any regional extinctions or ecosystem reorganizations. In the study area, onset of the

  1. A new method for carbon isotopic analysis of protein

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, D.E. (Lawrence Livermore National Lab., CA (USA))

    1991-02-01

    The reaction of ninhydrin with amino acids can be used in carbon isotopic studies of protein. The reaction can be applied to extract as carbon dioxide only peptide-bonded carbon in proteinaceous material, thus avoiding most, if not all, contaminants. Test radiocarbon dates on ancient bone indicate that the method provides reliable ages, and stable carbon isotopic data suggest that our understanding of isotopic dietary reconstruction needs detailed examination. The technique should also be useful in biochemical tracing experiments and in global carbon budget studies, and the underlying principle may be applicable to other isotopes and molecules. 28 refs., 1 fig., 1 tab.

  2. Hydrogen isotope adsorption on nano-carbons

    Energy Technology Data Exchange (ETDEWEB)

    Hideki, Tanaka; Daisuke, Noguchi [Chiba Univ., Diversity and Fractal Science, Graduate School of Science and Technology, (Japan); Hirofumi, Kanoh; Katsumi, Kaneko [Chiba Univ., Dept. of Chemistry, Faculty of Science (Japan)

    2005-07-01

    Hydrogen adsorption on carbonaceous materials has received considerable attention in recent decades, because physisorption of hydrogen was considered to be the most promising hydrogen storage technology to achieve the US Department of Energy (DOE) target for fuel cell powered vehicles. Many simulation studies of hydrogen adsorption on single-wall carbon nano-tubes (SWNTs) and graphitic slit pores have been performed by assuming that hydrogen can be modeled as a classical fluid above 77 K, to predict their hydrogen storage capacities; however, Wang et al. recently developed path integral grand canonical Monte Carlo (PI-GCMC) technique to explore statistical properties of quantum fluids [1] and then they applied the PI-GCMC simulation to a study of hydrogen adsorption on SWNTs including quantum effects [2]. Surprisingly, they showed that quantum effects are very important even at 298 K for adsorption in interstices of SWNT bundles: the interstitial adsorption of hydrogen from the quantum simulations is quite smaller than that from classical simulations. Recently, we also showed that quantum effects on adsorption of hydrogen isotopes on single-wall carbon nano-horn (SWNH) are significant at 77 K by comparing experiment and simulations [3]. We have thus measured adsorption isotherms of H{sub 2} and D{sub 2} on nano-carbons [activated carbon fibers (ACFs) and single-wall carbon nano-tubes (SWNTs)] to evaluate quantum effects on adsorption at low temperatures, and found that, for example, adsorption of H{sub 2} on ACFs are about 10% larger than D{sub 2} at 77 K and 0.1 MPa. We have also performed grand canonical Monte Carlo (GCMC) simulations for hydrogen isotope adsorption on graphitic slit pore, SWNT and SWNT bundle models. Quantum effects were incorporated in the simulations through the Feynman-Hibbs (FH) effective potential based on the classical Lennard-Jones (LJ) potential. Fig. 1 shows simulated hydrogen isotope adsorption isotherms on the (10,10) nano-tube bundle

  3. Hydrogen isotope adsorption on nano-carbons

    Energy Technology Data Exchange (ETDEWEB)

    Hideki Tanaka; Daisuke Noguchi [Diversity and Fractal Science, Graduate School of Science and Technology, Chiba University 1-33 Yayoi, Inage, Chiba 263-8522, (Japan); Hirofumi Kanoh; Katsumi Kaneko [Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, (Japan)

    2005-07-01

    Hydrogen adsorption on carbonaceous materials has received considerable attention in recent decades, because physi-sorption of hydrogen was considered to be the most promising hydrogen storage technology to achieve the US Department of Energy (DOE) target for fuel cell powered vehicles. Many simulation studies of hydrogen adsorption on single-wall carbon nano-tubes (SWNTs) and graphitic slit pores have been performed by assuming that hydrogen can be modeled as a classical fluid above 77 K, to predict their hydrogen storage capacities; however, Wang et al. recently developed path integral grand canonical Monte Carlo (PI-GCMC) technique to explore statistical properties of quantum fluids and then they applied the PI-GCMC simulation to a study of hydrogen adsorption on SWNTs including quantum effects. Surprisingly, they showed that quantum effects are very important even at 298 K for adsorption in interstices of SWNT bundles: the interstitial adsorption of hydrogen from the quantum simulations is quite smaller than that from classical simulations. Recently, we also showed that quantum effects on adsorption of hydrogen isotopes on single-wall carbon nano-horn (SWNH) are significant at 77 K by comparing experiment and simulations. We have thus measured adsorption isotherms of H{sub 2} and D{sub 2} on nano-carbons [activated carbon fibers (ACFs) and single-wall carbon nano-tubes (SWNTs)] to evaluate quantum effects on adsorption at low temperatures, and found that, for example, adsorption of H{sub 2} on ACFs are about 10% larger than D{sub 2} at 77 K and 0.1 MPa. We have also performed grand canonical Monte Carlo (GCMC) simulations for hydrogen isotope adsorption on graphitic slit pore, SWNT and SWNT bundle models. Quantum effects were incorporated in the simulations through the Feynman-Hibbs (FH) effective potential based on the classical Lennard-Jones (LJ) potential. Fig. 1 shows simulated hydrogen isotope adsorption isotherms on the (10,10) nano-tube bundle at 77 K

  4. 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....... The fractionation of Cr isotopes during calcium carbonate coprecipitation was assumed to be small, based on previously published data of modern seawater and modern non-skeletal marine carbonates. However, results from this study for rapidly precipitated calcium carbonate in the presence of chromate show a tendency...... showed the presence of vaterite. Calcium carbonate crystals were also precipitated in a double diffusion silica hydrogel over a longer period of time resulting in samples consisting of micrometric-millimetric calcite crystals, which were again significantly enriched in heavy Cr isotopes compared...

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

    Science.gov (United States)

    Boehme, Susan E.

    1993-01-01

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

  6. 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.

  7. Carbon isotope fractionation for cotton genotype selection

    Directory of Open Access Journals (Sweden)

    Giovani Greigh de Brito

    2014-09-01

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

  8. 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.

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

    Science.gov (United States)

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

    2016-06-01

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

  10. Late Paleocene–early Eocene carbon isotope stratigraphy from a ...

    Indian Academy of Sciences (India)

    Here, for the first time, we report high resolution carbon isotope (13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial ...

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    climatic changes. We here present results of a new isotopic tracer system – stable chromium isotopes – applied to a late Ediacaran marine carbonate sequence exposed in the Calera de Recalde syncline, Arroyo del Soldado Group, Uruguay. The aim was to compare Cr isotope signatures directly to d13C, 87Sr/86Sr...... and 143Nd/144Nd fluctuations in a well defined stratigraphic profile comprising sediments that were deposited during cold–warm periods ccompanied by sea-level changes in response to glaciation–deglaciation at higher latitudes. The studied section is characterized by a pronounced negative (down to -3.3‰) d...... hydrothermal input into the basin at his time) implies that CO2 limitation was the cause of negative d13C and d53Cr excursions in otherwise nutrient rich late Neoproterozoic basins, and that glaciation is only one more consequence of a tectonically driven, biologically mediated system. In such a scenario...

  12. Constraining the cause of the end-Guadalupian extinction with coupled records of carbon and calcium isotopes

    Science.gov (United States)

    Jost, A. B.; Mundil, R.; He, B.; Brown, S. T.; Altiner, D.; Sun, Y.; DePaolo, D. J.; Payne, J.

    2013-12-01

    A negative δ13C excursion in carbonate sediments from Guadalupian (Middle Permian) and Lopingian (Late Permian) stratigraphic sections has been interpreted to result from a large carbon cycle disturbance during end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbations to the global carbon cycle. The carbon and calcium cycles are coupled via CaCO3 burial, so changes in calcium isotopes can be used to constrain the cause of a carbon isotope excursion. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China and Turkey. Isotope records among our studied sections are inconsistent in both their δ13C and δ44/40Ca records. Similar inconsistencies in δ13C among sections occur across previously published datasets. Sections with large (>3‰) changes in δ13C either show evidence for diagenetic alteration or do not show δ13C and δ44/40Ca changes consistent with severe volcanic degassing from Emeishan or methane clathrate destabilization. We conclude that the large isotopic changes are more likely the result of local burial conditions or diagenetic effects, rather than a large carbon cycle disturbance. Perturbations to the global carbon and calcium cycles appear to have been much smaller across the G/L transition than across the subsequent Permian-Triassic boundary. This finding is consistent with recent paleobiological data showing that the end-Guadalupian extinction was much less severe than previously believed, and was indistinguishable in magnitude from background intervals. However, selective extinction of marine animals with passive respiratory physiology indicates that the G/L extinction cannot simply be due to background extinction or sampling failure, and that it was triggered by some environmental event. Therefore, any environmental event must have been small enough to not generate large

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-12-31

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

  14. Reconstructing changes in marine carbonate production during the PETM using stable strontium isotopes

    Science.gov (United States)

    Pearce, C. R.; Parkinson, I. J.; Foster, L. C.; Schmidt, D. N.

    2012-12-01

    The Palaeocene-Eocene Thermal Maximum (PETM) at ~55Ma represents a global climatic optimum that is characterised by an increase in sea surface temperatures and a co-incident increase in continental weathering rates1-3. It is also associated with an abrupt negative δ13C excursion that is indicative of a large and rapid input of isotopically light carbon into the ocean-atmosphere system4. This sudden release of carbon during the PETM had a major impact on the marine carbonate system, and resulted in the dissolution of carbonates in the deep oceans and associated shoaling of the carbonate compensation depth (ccd) due to a depletion in the availability of the carbonate ion2,5. This study provides new constraints on the changes in the marine carbonate flux during the PETM event using the stable strontium isotope system (δ88/86Sr). The long residence time of Sr in the oceans (~2.5 Ma) means that seawater has an isotopically homogenous δ88/86Sr composition that is dependent on the balance between the principle Sr inputs (rivers, hydrothermal fluids and porewaters) and outputs (incorporation into carbonate)6. Changes in the flux of Sr to the oceans during the PETM can be accounted for using the radiogenic Sr isotope system (87Sr/86Sr), enabling variations in δ88/86Sr to be attributed to shifts in the carbonate output flux. New δ88/86Sr, 87Sr/86Sr and Sr/Ca data from the PETM are presented from well-preserved planktonic foraminifera collected from Shatsky Rise in the Pacific Ocean. Foraminiferal calcite has been demonstrated to preserve the δ88/86Sr composition of seawater7, and all samples were handpicked to ensure that only specific species and size fractions were analysed. The new data is compared to previously reported variations in Sr/Ca ratios from the Pacific Ocean, Southern Ocean and Tropical Atlantic3, and the implications for global carbonate dissolution as a consequence of ocean acidification during the PETM are discussed. (1)Zachos et al. (2003). Science

  15. Secondary origin of negative carbon isotopic series in natural gas

    Directory of Open Access Journals (Sweden)

    Jinxing Dai

    2016-02-01

    Full Text Available The carbon isotopic series of alkane gases were divided into three types: (1 positive carbon isotopic series: δ13C values increased with increasing carbon numbers among the C1–C4 alkanes, which is a typical characteristic for primary alkane gases; (2 negative carbon isotopic series: δ13C values decreased with increasing carbon numbers among the C1–C4 alkanes; and (3 partial carbon isotopic reversal, which had no increasing or decreasing relationship between the δ13C values and carbon numbers. Negative carbon isotopic series were further divided into primary and secondary origins. The primary is a typical characteristic of abiogenic gases, while the secondary is a result of the secondary alteration imposed on biogenic gases usually observed in over-mature shale gas and coal-derived gas. Previous research has proposed several possible explanations for negative carbon isotopic series of secondary origin, such as secondary cracking, diffusion, and the Rayleigh fractionation of ethane and propane through redox reaction with the participation of transition metal and water at 250–300 °C. After a comparative study, the authors found that the negative carbon isotopic series of secondary origin for both shale gas and coal-derived gas appeared in areas where source rocks (shales were at an over-mature stage, but not in areas where source rocks (shales were only at a high-maturity stage. As a result, high maturity (>200 °C was the main controlling factor for the occurrence of negative carbon isotopic series of secondary origin in thermogenic gases. Within this maturity interval, secondary cracking, diffusion, and Rayleigh fractionation of ethane and propane could happen separately or together.

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

    Science.gov (United States)

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

    2016-11-01

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

  17. A biomarker record of Lake El'gygytgyn, Far East Russian Arctic: investigating sources of organic matter and carbon cycling during marine isotope stages 1–3

    Directory of Open Access Journals (Sweden)

    A. R. Holland

    2013-01-01

    Full Text Available Arctic paleoenvironmental archives serve as sensitive recorders of past climate change. Lake El'gygytgyn (Far East Russian Arctic is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact 3.58 Ma ago. Prior research on sediments collected from Lake El'gygytgyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (δ13C values. Here we investigate the abundance and carbon isotopic composition of lipid biomarkers recovered from Lake El'gygytgyn sediments spanning marine isotope stages 1–3 to identify key sources of organic matter (OM to lake sediments, to establish which OM sources drive the negative δ13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1–3, direct evidence for water column anoxia is lacking. A ~4‰ negative excursion in bulk sediment δ13C values during the Local Last Glacial Maximum (LLGM is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol δ13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative δ13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide

  18. Variation in carbon and nitrogen stable isotope ratios in flight ...

    African Journals Online (AJOL)

    bellied Sunbird to assess the value of using stable isotopes of feathers in avian dietary studies. Significant variation in δ13C and δ15N isotope values of flight feathers (range = 3.1‰ and 2.7‰, respectively) indicated that the source of carbon (i.e. ...

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

    Science.gov (United States)

    Zakon, Yevgeni; Halicz, Ludwik; Gelman, Faina

    2013-12-17

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

  20. Stable carbon isotope ratios from archaeological charcoal as palaeoenvironmental indicators

    CSIR Research Space (South Africa)

    Hall, G

    2008-01-01

    Full Text Available The potential to provide environmental proxies using stable carbon isotopes from modern and archaeological charcoal is explored. Experiments on modern Podocarpus (Yellowwoods) show that δ13C values of stems, branches and charcoal preserve proxy...

  1. Diagenetic origin of carbon and oxygen isotope compositions of Permian Triassic boundary strata

    Science.gov (United States)

    Heydari, Ezat; Wade, William J.; Hassanzadeh, Jamshid

    2001-09-01

    Bulk carbonate δ13C and δ18O compositions of profiles across Permian-Triassic (P-T) boundary sections in China, Italy, Austria, and Iran show wide varieties of trends. The δ13C depletions occur in all sections and range from 2 to 8‰ PDB in magnitude. These excursions take place over intervals ranging from less than 0.1 to more than 40 m. The δ18O values may increase or decrease toward the P-T boundary, but decrease sharply by 2-9‰ PDB at or above the boundary. Cross-plots of δ13C and δ18O values from all sections show positive covariance. Wide differences in magnitudes, trends, and position of the excursions relative to the boundary, as well as the covariance patterns suggest that P-T boundary δ18O and δ13C values are partially or entirely diagenetic in origin, formed in association with exposure surfaces. This interpretation implies that P-T boundary sections studied till date were subaerially exposed before, during, and after the mass extinction, resulting in the removal of strata containing key information about the extinction mechanism. This inference is consistent with the paleontological studies that have shown the presence of gaps at the boundary, and further supported by the sharp lithologic changes observed at virtually all P-T boundary sections. Subaerial exposures are documented by detailed sedimentologic and isotopic studies from central Tethyan sections in Abadeh and Shah Reza in Iran. Proposed P-T boundary extinction models are based on isotopic values that are diagenetic in origin and stratigraphic sections that are incomplete, leading to extinction mechanisms with little physical supporting evidence.

  2. Carbon and hydrogen isotope fractionation during anaerobic quinoline degradation.

    Science.gov (United States)

    Fischer, Anko; Weber, Stefanie; Reineke, Anne-Kirsten; Hollender, Juliane; Richnow, Hans-H

    2010-09-01

    Quinoline is a N-heterocyclic compound often found at tar oil contaminated field sites. To provide information whether stable isotope analysis can help to characterize the fate of quinoline within contaminated aquifers, carbon and hydrogen isotope fractionation of quinoline were investigated during biodegradation under sulfate-reducing conditions. No significant carbon isotope effect was observed, however, substantial hydrogen isotope fractionation was detected. Thus, hydrogen isotope fractionation may be used as an indicator for in situ biodegradation of quinoline. The bulk hydrogen isotope enrichment factor was εH(bulk)=-33±12‰. During the biodegradation of quinoline the primary intermediate 2-hydroxyquinoline was detected indicating hydroxylation at the C2-position. According to this reaction mechanism, the reactive position specific hydrogen enrichment factor (εH(reactive position)) and apparent kinetic hydrogen isotope effect (AKIE(H)) were calculated and gave values of εH(reactive position)=-205±75‰ and AKIE(H)=1.26±0.12, respectively. The missing carbon isotope effect may be explained by strong masking or an enzymatic direct side-on insertion of oxygen from the MoOH(H) group of the molybdenum center across the CH bond at the C2-position of quinoline with concomitant hydride transfer. The later assumption is supported by recent studies showing that initial step of hydroxylation of N-heteroaromatic compounds proceeds via a similar reaction mechanism. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. Organic carbon isotope values from the Late Permian Seis/Siusi succession (Dolomites, Italy: Implications for palaeoenvironmental changes

    Directory of Open Access Journals (Sweden)

    S. Siegert

    2011-08-01

    Full Text Available The Permian-Triassic boundary is marked by a globally prominent negative carbon isotope excursion traceable in marine carbonates and organic matter. In the shallow marine carbonate succession at Seis/Siusi (Dolomites, Italy, the δ13Ccarb and δ13Corg signatures follow the general Permian-Triassic boundary carbon isotope trend, but the δ13Corg values are slightly less depleted in 13C in two episodes representing restricted lagoonal environments and in the period around the Tesero Oolite Horizon. This isotopically less depleted organic matter in the lagoons is interpreted to be most likely caused by poor oxygen ventilation and/or slightly modified salinity which may have led to restricted bioproductivity and increased hence the relative amounts of continental-sourced organic matter. In addition, elevated riverine influx and supply of terrestrial organic matter, perhaps triggered by a wet period, might be the cause for the relatively less depleted 13C in the organic matter around the Tesero Oolite Horizon and in overlying sediments. doi:10.1002/mmng.201100008

  4. 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...

  5. elemental and isotopic compositions of organic carbon and nitrogen ...

    African Journals Online (AJOL)

    ABSTRACT. A 29 cm long core recovered from a water depth of 5 m in a small closed lake located in the. Empakai crater northern Tanzania, is used to document the contents of organic carbon and nitrogen, stable isotopes composition of organic carbon and nitrogen, and C/N ratios and to infer climatic changes from these ...

  6. Cruise tourism shore excursions

    DEFF Research Database (Denmark)

    João Lopes, Maria; Dredge, Dianne

    2018-01-01

    Very complex yet highly integrated business logics characterise cruise tourism with shore excursions frequently identified as a key source of value. This paper presents a case study of cruise tourism and shore excursion planning in Copenhagen, Denmark. The aim of this paper is to investigate...... the characteristics of cruise tourism, itinerary and shore excursion planning with a view to understanding the value generated from cruise tourism shore excursions. We argue that economic value is a blunt measure, and there are other types of value, positive and negative, that are also generated. This research...... reveals that a range of local conditions and structural characteristics create barriers and opportunities for generating different types of value. Using a case study of shore excursions in Copenhagen, the Baltic’s most important port, this paper explains the dynamics between cruise tourism and shore...

  7. Carbon isotope heterogeneities in deep Earth: Recycling of surface carbon or from core?

    Science.gov (United States)

    Satish-Kumar, Madhusoodhan

    2017-04-01

    Subduction of crustal materials, mantle melting and upwelling of deep mantle, in addition to a potential source from the core, largely controls the Earth's deep carbon cycle. Large variations in carbon isotopic composition between different reservoirs have been used widely to differentiate the source of carbon and to understand the carbon inventories and its recycling processes. However, how far high-temperature and hign-pressure conditions can affect the carbon isotope distribution, is a question still unanswered to clearly address the deep carbon cycle. I present here a review on carbon isotope fractionation processes in deep Earth and critically evaluate whether we can easily differentiate between surface carbon and deep carbon based on isotope characteristics. Recent experimental carbon isotope fractionation studies in the Fe-C system suggests that light carbon is selectively partition into metallic core during early magma ocean environment (Satish-Kumar et al., 2011). Furthermore, carbonate melts can be a medium for efficient crystallisation of diamonds in Earth's mantle (Palyanov et al., 2013). Rayleigh fractionation modelling based on fractionation suggests that core can be a reservoir of 12C enriched carbon and can itself form a reservoir which can cause heterogeneity in mantle carbon (Wood et al., 2013). In addition, high pressure experiments in the carbon-saturated model harzburgite system (Enstatite-Magnesite-Olivine-Graphite), carbonated silicate melting resulted in 13C enrichment in the carbon dissolved in the silicate melt relative to elemental graphite (Mizutani et al., 2014). 13C enrichment in carbonate melt were further confirmed in experiments where redox melting between olivine and graphite produced a carbonate melt as well as carbonate reduction experiments to form graphite. A third factor, still unconquered is the effect of pressure on isotope fractionation process. Theoretical studies as well as preliminary experimental studies have suggested

  8. Carbon and Oxygen Isotope Ratios in Rona Limestone, Romania

    Directory of Open Access Journals (Sweden)

    Stela Cuna

    2001-04-01

    Full Text Available The carbon and oxygen isotopic compositions of limestones provide criteria for the evaluation of the depositional environment. For Jurassic and younger samples, the best discrimination between marine and fresh-water limestones is given by Z parameter, calculated as a linear correlation between δ13C and δ18O (‰ PDB. Rona Limestone (Upper Paleocene - Lower Eocene, outcropping on a small area in NW Transylvania (Meseş area is a local lacustrine facies. There, it divides Jibou Formation into the Lower Red Member and the Upper Variegated Member, respectively. Recently, a sequence containing a marine nannoplankton assemblage was identified in the base of Rona deposits. The main goal of our study was to characterize, based on the isotopic record, the primary environment of formation of the deposit, as well as that in which some diagenetic processes (the formation of dolomite and of green clay around the siliceous chert nodules took place. Ten samples representing limestones, dolomitic limestone, marls and the green carbonate-rich clay were studied from petrographical and mineralogical points of view, and the carbon and oxygen isotopic ratios from the carbonate (calcite component were measured. In conclusion, it was found that the procedure of extraction of CO2 we used enabled the discrimination between the isotopic prints of calcite vs. dolomite. This pleads for considering our results as a primary isotopic pattern in the bulk rock. The oxygen and carbon isotope data indicate a fresh-water depositional environment with Z<120. The δ13C mean value (-4.96 ‰ PDB is, generally, representative for fresh-water carbonates of the Tertiary period. The same environment characterized also the formation of carbonates within the green clay.

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

    Directory of Open Access Journals (Sweden)

    A. Kornilova

    2016-09-01

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

  10. Characteristics of stable carbon isotopic composition of shale gas

    Directory of Open Access Journals (Sweden)

    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.

  11. Distinct carbon isotope fractionation during anaerobic degradation of dichlorobenzene isomers.

    Science.gov (United States)

    Liang, Xiaoming; Mundle, Scott O C; Nelson, Jennifer L; Passeport, Elodie; Chan, Calvin C H; Lacrampe-Couloume, Georges; Zinder, Stephen H; Sherwood Lollar, Barbara

    2014-05-06

    Chlorinated benzenes are ubiquitous organic contaminants found in groundwater and soils. Compound specific isotope analysis (CSIA) has been increasingly used to assess natural attenuation of chlorinated contaminants, in which anaerobic reductive dechlorination plays an essential role. In this work, carbon isotope fractionation of the three dichlorobenzene (DCB) isomers was investigated during anaerobic reductive dehalogenation in methanogenic laboratory microcosms. Large isotope fractionation of 1,3-DCB and 1,4-DCB was observed while only a small isotope effect occurred for 1,2-DCB. Bulk enrichment factors (εbulk) were determined from a Rayleigh model: -0.8 ± 0.1 ‰ for 1,2-DCB, -5.4 ± 0.4 ‰ for 1,3-DCB, and -6.3 ± 0.2 ‰ for 1,4-DCB. εbulk values were converted to apparent kinetic isotope effects for carbon (AKIE) in order to characterize the carbon isotope effect at the reactive positions for the DCB isomers. AKIE values are 1.005 ± 0.001, 1.034 ± 0.003, and 1.039 ± 0.001 for 1,2-DCB, 1,3-DCB, and 1,4-DCB, respectively. The large difference in AKIE values between 1,2-DCB and 1,3-DCB (or 1,4-DCB) suggests distinct reaction pathways may be involved for different DCB isomers during microbial reductive dechlorination by the methanogenic cultures.

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

    NARCIS (Netherlands)

    Sluijs, A.|info:eu-repo/dai/nl/311474748; 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

  13. 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

  14. Salinity of the Eocene Arctic Ocean from oxygen isotope analysis of fish bone carbonate

    Science.gov (United States)

    Waddell, Lindsey M.; Moore, Theodore C.

    2008-03-01

    Stable isotope analysis was performed on the structural carbonate of fish bone apatite from early and early middle Eocene samples (˜55 to ˜45 Ma) recently recovered from the Lomonosov Ridge by Integrated Ocean Drilling Program Expedition 302 (the Arctic Coring Expedition). The δ18O values of the Eocene samples ranged from -6.84‰ to -2.96‰ Vienna Peedee belemnite, with a mean value of -4.89‰, compared to 2.77‰ for a Miocene sample in the overlying section. An average salinity of 21 to 25‰ was calculated for the Eocene Arctic, compared to 35‰ for the Miocene, with lower salinities during the Paleocene Eocene thermal maximum, the Azolla event at ˜48.7 Ma, and a third previously unidentified event at ˜47.6 Ma. At the Azolla event, where the organic carbon content of the sediment reaches a maximum, a positive δ13C excursion was observed, indicating unusually high productivity in the surface waters.

  15. Late Triassic tropical climate of Pangea: Carbon isotopic and other insights into the rise of dinosaurs

    Science.gov (United States)

    Whiteside, J. H.; Lindström, S.; Irmis, R. B.; Glasspool, I.; Schaller, M. F.; Dunlavey, M.; Nesbitt, S. J.; Smith, N. D.; Turner, A. H.

    2015-12-01

    The rarity and species-poor nature of early dinosaurs and their relatives at low paleolatitudes persisted for 30 million years after their origin and 10-15 million years after they became abundant and speciose at higher latitudes. New environmental reconstructions from stable carbon isotope ratios of preserved organic matter (δ13Corg), atmospheric pCO2 data based on the δ13C of soil carbonate, palynological, and wildfire data from charcoal from early dinosaur-bearing strata at low paleolatitudes in western North America show that variations in δ13Corg and palynomorph ecotypes are tightly correlated, displaying large and high-frequency excursions. These variations occurred within an environment characterized by elevated and increasing atmospheric pCO2, pervasive wildfires, and rapidly fluctuating extreme climatic conditions. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions until the end-Triassic, the large-bodied, fast-growing tachymetabolic dinosaurian herbivores were not. We hypothesize that the greater resources required by the herbivores made it difficult from them to adapt to the unstable conditions at low paleolatitudes in the Late Triassic.

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

    Science.gov (United States)

    Blättler, Clara L.; Higgins, John A.

    2017-12-01

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

  17. Determination of porphyrin carbon isotopic composition using gas chromatography-isotope ratio monitoring mass spectrometry.

    Science.gov (United States)

    Yu, Z; Sheng, G; Fu, J; Peng, P

    2000-12-01

    Carbon isotopic compositions of aetio I occurring in the form of free-base, nickel, demetallation, dihydroxysilicon(IV) and bis(tert.-butyldimethylsiloxy)silicon(IV) [(tBDMSO)2Si(IV)] have shown that it has experienced no obvious isotope fractionation during the synthesis of [(tBDMSO)2Si(IV)] porphyrin from aetio I. Here, aetio I porphyrin species such as free-base, nickel, demetallated and dihydroxysilicon were analyzed by the conventional method, namely it is combusted in sealed system, and followed by isotope ratio monitoring mass spectrometric analysis. [(tBDMSO)2Si(IV)] aetio I was assayed by gas chromatography-isotope ratio monitoring mass spectrometry (GC-IRMS). A porphyrin mixture of [(tBDMSO)2Si(IV)] aetio I and octaethylporphyrin was also prepared. Their carbon isotopic compositions measured by GC-IRMS indicate that no isotope exchange took place between the porphyrins during the synthesis of [(tBDMSO)2Si(IV)] porphyrins. This method is employed for delta13C determination of geoporphyrins from the Maoming and Jianghan oil shales.

  18. CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes

    NARCIS (Netherlands)

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

    Carbon isotope fractionation (εp) between the inorganic carbon source and organic matter has been proposed to be a function of pCO2. To understand the CO2-dependency of εp and species-specific differences therein, inorganic carbon fluxes in the four dinoflagellate species Alexandrium fundyense,

  19. Chromium isotope fractionation during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

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

    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...... to no Cr isotope fractionation in the oceans. These experiments represent a first step toward understanding the Cr isotope signal of carbonates where fractionations will likely be ≤ 0.3 ‰ and as such, pave the way for future work to enable a reliable application of the Cr isotope proxy. References: [1] Hua...... et al., 2007, Water Air Soil Poll. 179, 381-390. [2] Sánchez-Pastor et al., 2011, Cryst. Growth Des. 11, 3081-3089....

  20. Lake Van carbonates: Implications for lacustrine stable isotope analysis

    Science.gov (United States)

    McCormack, Jeremy; Immenhauser, Adrian; Kwiecien, Ola

    2017-04-01

    Carbonate stable isotope (δ18O and δ13C) analysis is a commonly applied and powerful proxy in lacustrine palaeoclimatology. In the absence of large quantities of detrital carbonates, the bulk carbonate is assumed to mainly represent inorganic carbonates precipitated in the epilimnion. In well-preserved, geologically young sediments (e.g. varves), post-depositional processes affecting the mineralogy or geochemistry of sedimentary carbonates are difficult to recognise. In case of terminal and alkaline Lake Van, the interpretation of the δ18O and δ13C signals of bulk carbonates is, in comparison to other proxies, far from straightforward when relying on traditional interpretative approaches. Consequently, using a multi-component approach we studied, individually and in detail, various components comprising Lake Van's bulk carbonates. Samples investigated here cover the last glacial/interglacial period. Inorganic ( 63 μm) carbonates were isolated by wet-sieving and analysed by means of XRD, SEM and isotope mass spectrometry. High-resolution mineralogical analysis revealed variable amounts of aragonite and calcite as well as early diagenetic non-stoichiometric (calcian) dolomite. The early diagenetic dolomite appears to be replacing the inorganic aragonite/calcite and occurs within finely-laminated, organic-rich sediments. Isotopically the dolomite differs significantly from the primary carbonates with typically heavier δ18O and lighter δ13C values. Thus, in the case of bulk sediment isotope analysis the presence of higher amounts of diagenetic dolomite is distorting the isotopic pattern. Ostracod valves represent biogenic carbonates. However, apart from well-preserved, translucent carapaces we have found coated ones, reoccurring throughout the profile within specific facies types. The coating, comprising mainly of aragonite has a significantly heavier δ18O and δ13C signature compared to coeval inorganic carbonates, precipitated presumably in the surface water

  1. The origin of carbon isotope vital effects in coccolith calcite

    Science.gov (United States)

    McClelland, H. L. O.; Bruggeman, J.; Hermoso, M.; Rickaby, R. E. M.

    2017-03-01

    Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive.

  2. LBA-ECO CD-08 Carbon Isotopes in Belowground Carbon Pools, Amazonas and Para, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains carbon isotope signatures from soil organic matter collected from the following sites: the forests of the ZF-2 INPA reserve...

  3. LBA-ECO CD-08 Carbon Isotopes in Belowground Carbon Pools, Amazonas and Para, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains carbon isotope signatures from soil organic matter collected from the following sites: the forests of the ZF-2 INPA reserve approximately 80...

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

    Indian Academy of Sciences (India)

    Stable carbon isotope analysis of fossil leaves from the Bhuj Formation, western India was carried out to infer the prevailing environmental conditions. Compression fossil leaves such as Pachypteris indica, Otozamite kachchhensis, Brachyphyllum royii and Dictyozamites sp. were recovered from three sedimentary ...

  5. 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 ...

  6. Measurements and interpretation of oxygen isotopes in stratospheric carbon dioxide

    NARCIS (Netherlands)

    Mrozek, D.J.

    2017-01-01

    Carbon dioxide (CO2) is an important natural and anthropogenic greenhouse gas in Earth's atmosphere. Its atmospheric mole fraction has increased from about 280 ppm (parts per million) in the pre-industrial atmosphere to more than 400 ppm at present. Investigation of the stable isotopic composition

  7. Stable carbon isotope fractionation by sulfate-reducing bacteria

    Science.gov (United States)

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

    2003-01-01

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

  8. Organic carbon isotope systematics of coastal marshes

    NARCIS (Netherlands)

    Middelburg, J.J.; Nieuwenhuize, J.; Lubberts, R.K.; Van de Plassche, O.

    1997-01-01

    Measurements of nitrogen, organic carbon and delta(13)C are presented for Spartina-dominated marsh sediments from a mineral marsh in SW Netherlands and from a peaty marsh in Massachusetts, U.S.A. delta(13)C Of organic carbon in the peaty marsh sediments is similar to that of Spartina material,

  9. 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.

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

    Science.gov (United States)

    Schubert, Brian A.; Jahren, A. Hope

    2012-11-01

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

  11. 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

  12. A supercritical oxidation system for the determination of carbon isotope ratios in marine dissolved organic carbon

    NARCIS (Netherlands)

    Le Clercq, Martijn; Van der Plicht, Johannes; Meijer, Harro A.J.

    1998-01-01

    An analytical oxidation system employing supercritical oxidation has been developed. It is designed to measure concentration and the natural carbon isotope ratios (C-13, C-14) Of dissolved organic carbon (DOC) and is especially suited for marine samples. The oxidation takes place in a ceramic tube

  13. Disequilibrium in Clumped Isotopes Caused by Diagenesis in Tertiary Carbonates

    Science.gov (United States)

    Murray, S.; Swart, P. K.

    2015-12-01

    This work examines the clumped isotopes and carbonate associated sulfate (CAS) within a system which is being altered from aragonite to calcite and being subjected to partial dolomitization within the marine realm. Samples were collected from Clino, a ≈670m long core which represents slope carbonates composed of varying percentages of aragonite, low-magnesium calcite (LMC), and dolomite. The concentrations of these endmembers differ dramatically over short distances and are associated with varying degrees of marine diagenesis. In the deeper water portion of the core, previous work has shown no evidence of exposure throughout nor is there any evidence for hydrothermal fluids existing in the Bahamas. Bulk samples were collected from the portions of the core in which dolomite was most prominent. Samples were treated and measured for CAS and for their clumped isotope value. They were then subjected to a series of buffered acetic acid leaches to remove the aragonite and LMC portion of the sample. There were up to three treatments per sample with the resulting sediment measured on XRD to determine its % dolomite composition. These treatments were then also measured for clumped isotopes. The δ34S of the sediments yielded values of up to 10‰ more positive than contemporaneous sweater and implicate bacterial sulfate reduction in the formation of these dolomites. Clumped isotope results of the separates allowed for the calculation of end-member formation temperatures for the LMC and dolomite, whilst using a mixing model to account for non-linearity in ∆47 between end-member combinations and varying ∆47-temperature equations. In contrast to other dolomites in the Bahamas proposed to have formed by massive flow of normal seawater, the Clino temperatures values were significantly elevated compared to the presumed equilibrium values. These data suggest that BSR may result in carbonates with clumped isotopic values significant elevated to equilibrium.

  14. 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.

  15. The weathering of organic carbon and pyrite sulfur in Earth's crust and its importance for regulating atmospheric composition, seawater chemistry, and stable isotope records

    Science.gov (United States)

    Reinhard, C. T.; Planavsky, N.; Bolton, E. W.

    2016-12-01

    Earth's crust stores extremely large reservoirs of organic carbon and pyrite sulfur, and transient or secular changes in the sizes of these reservoirs have the capacity to dramatically alter atmospheric composition, climate, seawater acid-base chemistry, and the propagation of isotopic signals into the geologic record. This talk will present and discuss new quantitative approaches toward better understanding the factors that control organic carbon and pyrite sulfur weathering under a wide range of Earth surface conditions, as well as their downstream effects on seawater chemistry, stability of atmospheric pO2, and conventional interpretations of stable carbon isotope mass balance during pivotal events in Earth's biogeochemical evolution. In particular, we will focus on (1) development of a weathering-driven scaling between atmospheric pO2 and geologic carbon isotope signals that explains the relative stability of marine δ13C through time and provides a mechanism for protracted negative δ13C excursions during transient increases in atmospheric pO2; (2) experimental and theoretical approaches aimed at better understanding the role of pyrite sulfur weathering in stabilizing atmospheric pO2; and (3) the importance of redox balance in the sedimentary rock cycle for controlling the marine carbonate system and atmospheric pCO2.

  16. Environmental change during the Late Berriasian - Early Valanginian: a prelude to the late Early Valanginian carbon-isotope event?

    Science.gov (United States)

    Morales, Chloé; Schnyder, Johann; Spangenberg, Jorge; Adatte, Thierry; Westermann, Stephane; Föllmi, Karl

    2010-05-01

    The Valanginian period is well known for a positive excursion in marine and terrestrial δ13C records, which has been interpreted as the consequence of a major perturbation in the global carbon cycle (Lini et al., 1992; Erba et al., 2004). In contrast to the positive δ13C excursions of the Early Aptian and latest Cenomanian, marine organic-rich sediments have only been recognized from a few localities (van de Schootbrugge et al., 2003; Reboulet et al., 2003; Gröcke et al., 2005; Westermann et al., in press). The δ13C excursion began in the late Early Valanginian (campylotoxus ammonite zone) and gradually ended during the Late Valanginian. It is associated with a phase of widespread carbonate-platform drowning on the shelf (Föllmi et al., 1994) and a decline in calcareous nannofossils in the pelagic realm (Erba et al., 2004). As a triggering mechanism, numerous authors invoke the formation of the Parañà-Etendeka flood basalt. The correlation of this episode with the Valanginian δ13C event depends, however, on the absolute ages attributed to the Valanginian stage. The recent geological timescale by Ogg et al. (2008) shows that the major eruptional phase occurred during the Late Valanginian. This may imply that the late Early Valanginian δ13C event resulted from a combination of different factors. Important paleoenvironmental change occurred already in the latest Berriasian and earliest Valanginian, prior to the positive δ13C excursion. An increase in nutrient input near the onset of the δ13C excursion (campylotoxus ammonite zone), which may be considered as a trigger of the carbon cycle perturbation, has been identified in different studies, (Hennig, 2003; Duchamp-Alphonse et al., 2007; Bornemann & Mutterlose, 2008). Heterozoan faunal associations became dominant since the Early Valanginian on the northern Tethyan Helvetic platform and may indicate the beginning of sea-water eutrophication (Föllmi et al., 2007). Clay assemblages in the Tethys and Western

  17. Fluid evolution in CM carbonaceous chondrites tracked through the oxygen isotopic compositions of carbonates

    Science.gov (United States)

    Lindgren, P.; Lee, M. R.; Starkey, N. A.; Franchi, I. A.

    2017-05-01

    The oxygen isotopic compositions of calcite grains in four CM carbonaceous chondrites have been determined by NanoSIMS, and results reveal that aqueous solutions evolved in a similar manner between parent body regions with different intensities of aqueous alteration. Two types of calcite were identified in Murchison, Mighei, Cold Bokkeveld and LaPaz Icefield 031166 by differences in their petrographic properties and oxygen isotope values. Type 1 calcite occurs as small equant grains that formed by filling of pore spaces in meteorite matrices during the earliest stages of alteration. On average, the type 1 grains have a δ18O of ∼32-36‰ (VSMOW), and Δ17O of between ∼2‰ and -1‰. Most grains of type 2 calcite precipitated after type 1. They contain micropores and inclusions, and have replaced ferromagnesian silicate minerals. Type 2 calcite has an average δ18O of ∼21-24‰ (VSMOW) and a Δ17O of between ∼-1‰ and -3‰. Such consistent isotopic differences between the two calcite types show that they formed in discrete episodes and from solutions whose δ18O and δ17O values had changed by reaction with parent body silicates, as predicted by the closed-system model for aqueous alteration. Temperatures are likely to have increased over the timespan of calcite precipitation, possibly owing to exothermic serpentinisation. The most highly altered CM chondrites commonly contain dolomite in addition to calcite. Dolomite grains in two previously studied CM chondrites have a narrow range in δ18O (∼25-29‰ VSMOW), with Δ17O ∼-1‰ to -3‰. These grains are likely to have precipitated between types 1 and 2 calcite, and in response to a transient heating event and/or a brief increase in fluid magnesium/calcium ratios. In spite of this evidence for localised excursions in temperature and/or solution chemistry, the carbonate oxygen isotope record shows that fluid evolution was comparable between many parent body regions. The CM carbonaceous chondrites

  18. Standardization and optimization of core sampling procedure for carbon isotope analysis in eucalyptus and variation in carbon isotope ratios across species and growth conditions

    CSIR Research Space (South Africa)

    Raju, M

    2011-11-01

    Full Text Available and optimization of core sampling procedure for carbon isotope analysis in eucalyptus and variation in carbon isotope ratios across species and growth conditions Mohan Raju, B#; Nuveshen Naidoo*; Sheshshaayee, M. S; Verryn, S. D*; Kamalkannan, R^; Bindumadhava... isotope analysis in Eucalyptus. Methods Expt 1: * Cores were taken from periphery to pith in 5 year old trees of Eucalyptus * Five half sib families of Eucalyptus grandis & E. urophylla were used ? Cores were further subdivided into 5 fragments...

  19. 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

  20. Retention of inorganic carbon-14 by isotopic exchange in soils

    Energy Technology Data Exchange (ETDEWEB)

    Sheppard, S.C.; Evenden, W.G

    1996-07-01

    Carbon-14 is present naturally and is a waste product of the nuclear industry. It is readily incorporated into biological materials and potential impacts have to be considered carefully. From underground waste repositories, much of any {sup 14}C released will be inorganic and will pass rapidly through most terrestrial environments because of gaseous transfer. However, there will be some {sup 14}C retained in soils, in both organic and inorganic forms. This study addresses retention of inorganic {sup 14}C through isotopic exchange with soil carbonates. An outdoor study with incubations lasting up to 24 mo was conducted. A carbonated sandy soil was used unamended, amended with additional carbonate, or amended with ground alfalfa (Medicago sativa L.). One set of soil containers was left open and another set gamma-sterilized and sealed. Volatilization of some of the {sup 14}C happened within minutes, with 98% lost in the alfalfa-amended soils and 56% lost in the carbonate-amended soil. However, the fractions remaining in all the soils had residence half-times of over 1000 d. Much of this retained {sup 14}C was still inorganic and had undergone isotopic exchange with the solid {sup 12}C minerals in the soil. A progressive extraction method was used to monitor the degree of isotopic exchange, and in certain treatments the exchange process was still measurably progressing after 12 mo of incubation. Clearly, assessments of the impacts of {sup 14}C releases to the terrestrial environment must account for these long-term reactions and retention of {sup 14}C in soils. (author)

  1. Biogeochemistry of a mesotrophic lake and it's carbon isotope geochemistry

    Science.gov (United States)

    Cheng, S.; Ehresman, W.; Sadurski, S. E.

    2010-12-01

    Crystal Lake, located in west-central Ohio, is the main lake of a series of 4 interconnected lakes. The location and orientation indicate that they are most likely moulin-induced glacial lakes. Crystal Lake is about 5 hectares (12.5 acres). The maximum depth and mean depth are about 11.9 meters and 3.8 meters, respectively. As a result of this high depth-to-surface area ratio, it creates a strong thermal stratification during warm season. The lake was classified as eutrophic lake. However, the water quality has improved in the past decades. The chlorophyll in the epillimnion and upper metalimlion is about 4 μg/l and the Secchi disk depth is about 3.0 meters (10 feet). It is therefore reclassified as mesotrophic lake. Dissolved oxygen maximum (15.6 ppm) and pH peak (8.6) existed at 4.1 meter on August 16, 2010. At around 7.3 meter, where redox potential reading shows a sudden change from oxidizing to reducing , a ~half meter layer of dense purple sulfur bacteria coincides with turbidity, chlorophyll, and sulfate maxima. The chemical depth profiles are a result of thermal stratification, oxygenic photosynthesis by algae, non-oxygenic photosynthesis by purple sulfur bacteria, and respiration in the hypolimnion. Precipitation of calcium carbonate in the epilimnion and metalimnion is coupled by it’s dissolution in the hypolimnion. The purpose of the current project is to present extensive background study to form the framework for quantifying the carbon isotope evolution with multiple reaction pathways. Carbon isotope composition of dissolved inorganic carbon is being analyzed. Wigley-Plummer-Pearson mass transfer model will be used for the quantification of carbon isotope reaction pathways.

  2. Stable carbon isotope fractionation as tracer of carbon cycling in anoxic soil ecosystems.

    Science.gov (United States)

    Blaser, Martin; Conrad, Ralf

    2016-10-01

    While the structure of microbial communities can nowadays be determined by applying molecular analytical tools to soil samples, microbial function can usually only be determined by physiological experiments requiring incubation of samples. However, analysis of stable isotope fractionation might be able to analyse microbial function without incubation in soil samples. We describe the limitations of diagnosing and quantifying carbon flux pathways in soil by using the determination of stable carbon isotope composition in soil compounds and emphasize the importance of determining stable isotope fractionation factors for defined biochemical pathways. Fractionation factors are sufficiently different for some central biochemical pathways in anaerobic degradation of organic carbon. Thus, it is possible to quantify the relative contribution of CH4 production by hydrogenotrophic or aceticlastic methanogenic pathways, and of acetate formation by chemolithotrophic (acetyl-CoA synthase) or heterotrophic (fermentation) pathways. In addition, stable isotope analysis may allow the differentiation between different organic substrates used for degradation, for example, the relative contribution of root exudation versus soil organic matter degradation, provided the different substrates are sufficiently distinct in their isotopic compositions (e.g., mixture of C3 and C4 plants) and the carbon conversion pathways display only small fractionation factors or are identical for the different substrates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Hydrogen recycle and isotope exchange from dense carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Clausing, R.E.; Heatherly, L.

    1987-03-01

    Dense carbon films were prepared by deposition from hydrogen plasmas to which methane was added. The initial hydrogen recycle coefficient from the films ranges from more than two to less than one. The films contain large amounts of hydrogen (up to 50 at. %). They adjust themselves to provide recycling coefficients near unity. Isotope changeover times tend to be long. The reservoir of hydrogen instantly available to the plasma to maintain or stabilize the recycle coefficient and isotopic composition of the plasma is 10/sup 15/ cm/sup -2/ or greater depending on film preparation, temperature, and prior plasma exposure conditions. Simulator observations tend to support and improve the understanding of the observations in TEXTOR and JET; however, they also point out the need for control of film deposition and operating parameters to provide desirable and reproducible properties. The films and the hydrogen isotopes they contain can be removed easily by plasma processes. Since the hydrogen in these films is relatively immobile except in the zone reached by energetic particles, or at temperatures above 400/sup 0/C, dense carbon films may be useful in managing the tritium recovery from near-term fusion experiments.

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

    NARCIS (Netherlands)

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

    2015-01-01

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

  5. Paleogeographic and paleo-oceanographic influences on carbon isotope signatures: Implications for global and regional correlation, Middle-Upper Jurassic of Saudi Arabia

    Science.gov (United States)

    Eltom, Hassan A.; Gonzalez, Luis A.; Hasiotis, Stephen T.; Rankey, Eugene C.; Cantrell, Dave L.

    2018-02-01

    Carbon isotope data (δ13C) can provide an essential means for refining paleogeographic and paleo-oceanographic reconstructions, and interpreting stratigraphic architecture within complex carbonate strata. Although the primary controls on global δ13C signatures of marine carbonates are well understood, understanding their latitudinal and regional variability is poor. To better constrain the nature and applications of δ13C stratigraphy, this study: 1) presents a new high-resolution δ13C stratigraphic curve from Middle to Upper Jurassic carbonates in the upper Tuwaiq Mountain, Hanifa, and lower Jubaila formations in central Saudi Arabia; 2) explores their latitudinal and regional variability; and 3) discusses their implications for stratigraphic correlations. Analysis of δ13C data identified six mappable units with distinct δ13C signatures (units 1-6) between up-dip and down-dip sections, and one unit (unit 7) that occurs only in the down-dip section of the study succession. δ13C data from the upper Tuwaiq Mountain Formation and the lower Hanifa Formation (units 1, 2), which represent Upper Callovian to Middle Oxfordian strata, and record two broad positive δ13C excursions. In the upper part of the Hanifa Formation (units 3-6, Early Oxfordian-Late Kimmeridgian), δ13C values decreased upward to unit 7, which showed a broad positive δ13C excursion. Isotopic data suggest similar δ13C trends between the southern margin of the Tethys Ocean (Arabian Plate; low latitude, represented by the study succession) and northern Tethys oceans (high latitude), despite variations in paleoclimatic, paleogeographic, and paleoceanographic conditions. Variations in the δ13C signal in this succession can be attributed to the burial of organic matter and marine circulation at the time of deposition. Our study uses δ13C signatures to provide independent data for chronostratigraphic constraints which help in stratigraphic correlations within heterogeneous carbonate successions.

  6. Paleoceanographic changes of surface and deep water based on oxygen and carbon isotope records during the last 130 kyr identified in MD179 cores, off Joetsu, Japan Sea

    Science.gov (United States)

    Ishihama, Saeko; Oi, Takeshi; Hasegawa, Shiro; Matsumoto, Ryo

    2014-08-01

    We reconstructed the paleoenvironmental history of surface and deep water over the last 130 kyr from oxygen and carbon isotope ratios of planktonic and benthic foraminifera in two cores (MD179-3312 and MD179-3304) from the Joetsu Basin, eastern margin of the Japan Sea. Our data showed that paleoceanographic changes such as influx of surface currents and vertical circulation were associated with global glacial-interglacial sea level change. Surface water conditions were influenced by the influx of Tsushima Current, East China Sea coastal or off-shore waters through the Tsushima Strait during interglacial or interstadial stages, and strongly affected by freshwater input during the glacial maximum. During interglacial maximums such as Marine Isotope Stages 1 and 5e, development of well-oxygenated bottom water was indicated. A density-stratified ocean with weak ventilation was inferred from the isotopic records of benthic foraminifera during the Last Glacial Maximum. Local negative excursions in carbon isotopes during deglacial or interglacial periods may suggest the dissolution of gas hydrates or methane seep activities.

  7. Chlorine and carbon isotopes fractionation during volatilization and diffusive transport of trichloroethene in the unsaturated zone.

    Science.gov (United States)

    Jeannottat, Simon; Hunkeler, Daniel

    2012-03-20

    To apply compound-specific isotope methods to the evaluation of the origin and fate of organic contaminants in the unsaturated subsurface, the effect of physicochemical processes on isotope ratios needs to be known. The main objective of this study is to quantify chlorine and carbon isotope fractionation during NAPL-vapor equilibration, air-water partitioning, and diffusion of trichloroethene (TCE) and combinations of these effects during vaporization in porous media. Isotope fractionation is larger during NAPL-vapor equilibration than air-water partitioning. During NAPL-vapor equilibration, carbon, and chlorine isotope ratios evolve in opposite directions although both elements are present in the same bond, with a normal isotope effect for chlorine (ε(Cl) = -0.39 ± 0.03‰) and an inverse effect for carbon (ε(C) = +0.75 ± 0.04‰). During diffusion-controlled vaporization in a sand column, no significant carbon isotope fractionation is observed (ε(C) = +0.10 ± 0.05‰), whereas fairly strong chlorine isotope fractionation occurs (ε(Cl) = -1.39 ± 0.06‰) considering the molecular weight of TCE. In case of carbon, the inverse isotope fractionation associated with NAPL-vapor equilibration and normal diffusion isotope fractionation cancel, whereas for chlorine both processes are accompanied by normal isotope fractionation and hence they cumulate. A source of contamination that aged might thus show a shift toward heavier chlorine isotope ratios.

  8. Textural and isotopic evidence for Ca-Mg carbonate pedogenesis

    Science.gov (United States)

    Diaz-Hernandez, J. L.; Sánchez-Navas, A.; Delgado, A.; Yepes, J.; Garcia-Casco, A.

    2018-02-01

    Models for evaluating the terrestrial carbon cycle must take into account not only soil organic carbon, represented by a mixture of plant and animal remains, but also soil inorganic carbon, contained in minerals, mainly in calcite and dolomite. Thick soil caliches derived from weathering of mafic and ultramafic rocks must be considered as sinks for carbon storage in soils. The formation of calcite and dolomite from pedogenic alteration of volcanic tephras under an aridic moisture regime is studied in an unusually thick 3-m soil profile on Gran Canaria island (Canary Islands, Spain). The biological activity of the pedogenic environment (soil respiration) releases CO2 incorporated as dissolved inorganic carbon (DIC) in waters. It drives the formation of low-magnesian calcite and calcian dolomite over basaltic substrates, with a δ13C negative signature (-8 to -6‰ vs. V-PDB). Precipitation of authigenic carbonates in the soil is accompanied by the formation of Mg-rich clay minerals and quartz after the weathering of basalts. Mineralogical, textural, compositional, and isotopic variations throughout the soil profile studied indicate that dolomite formed at greater depths and earlier than the calcite. The isotopic signatures of the surficial calcite and deeper dolomite crusts are primary and resulted from the dissolution-precipitation cycles that led to the formation of both types of caliches under different physicochemical conditions. Dolomite formed within a clay-rich matrix through diffusive transport of reactants. It is precipitated from water with more negative δ18O values (-1.5 to -3.5‰ vs. V-SMOW) in the subsoil compared to those of water in equilibrium with surficial calcite. Thus, calcite precipitated after dolomite, and directly from percolating solutions in equilibrium with vadose water enriched in δ18O (-0.5 to +1.5‰) due to the evaporation processes. The accumulation of inorganic carbon reaches 586.1 kg m-2 in the soil studied, which means that the

  9. Stable isotope mass balances versus concentration differences of dissolved inorganic carbon - implications for tracing carbon turnover in reservoirs.

    Science.gov (United States)

    Barth, Johannes A C; Mader, Michael; Nenning, Franziska; van Geldern, Robert; Friese, Kurt

    2017-08-01

    The aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two pre-reservoirs in the Harz Mountains (Germany) were investigated for their dissolved and particulate carbon contents (dissolved inorganic carbon (DIC), dissolved organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC concentration depth profiles from March 2012 had an average of 0.33 mmol L-1. Increases in DIC concentrations later on in the year often corresponded with decreases in its carbon isotope composition (δ13CDIC) with the most negative value of -18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of -28.5 ‰ from DOC and -23.4, -31.8 and -30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its concentrations and δ13CDIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.

  10. Limitations and opportunities for Permian-Triassic carbonate-carbon isotope stratigraphy posed by microbial-controlled diagenetic mineral additions

    Science.gov (United States)

    Schobben, Martin; van de Velde, Sebastiaan; Suchocka, Jana; Leda, Lucyna; Korn, Dieter; Struck, Ulrich; Vinzenz Ullmann, Clemens; Hairapetian, Vachik; Ghaderi, Abbas; Korte, Christoph; Newton, Robert J.; Poulton, Simon W.; Wignall, Paul B.

    2017-04-01

    Bulk-carbonate stable carbon isotope records are used to proxy the ancient biogeochemical carbon cycle as well as aid in determining the age of sedimentary deposits. However, the multicomponent nature and the component-specific diagenetic potential of bulk-rock pose limits on the applicability of this proxy in recording ancient seawater chemistry and its usability as a stratigraphic aid. The aim of this study is to disentangle primary trends from diagenetic signals in carbonate-carbon isotope records traversing the Permian-Triassic boundary in marine carbonate-bearing sequences of Iran and South China. We observe, 1) a global first-order trend towards depleted carbon isotope values across the Permian-Triassic transition, 2) second-order carbon isotope variability superimposed on the first-order trend, and 3) a temporal trend in the amplitude of the second-order carbon isotope fluctuations. By application of a diagenetic model, we show that microbial-steered carbonate additions can introduce diagenetic carbon isotope signals to the carbonate archive. Organic carbon sedimentation has the potential to fuel this (sub)seafloor microbial pathway of carbonate stabilization and determines trajectories of diagenetic bulk-rock carbon isotope alteration. Moreover, we identified through this numerical exercise that lowered marine sulfate levels makes the sedimentary system vulnerable to diagenetic modulations of the primary carbon isotope signal, by modest changes of organic carbon supply. This approach suggests that latest Permian reduced bioturbation, consequential heterogeneous organic matter accumulation and authigenic mineralization can explain the temporal trend of increased second-order carbon isotope scatter, whilst retaining the first-order trend. In conclusion, the combined dataset and calculations suggest that the application of carbon isotope chemostratigraphy of the Permian-Triassic boundary is at present limited to the recognition of broad temporal patterns

  11. Carbon isotopic compositions of the Cambrian-Ordovician carbonates in Tarim Basin

    Energy Technology Data Exchange (ETDEWEB)

    Peng, S.; He, H.; Shao, L.; Shi, Z.; Gao, Y. [China University of Mining and Technology, Beijing (China). Dept of Resource Exploitation Engineering

    2002-07-01

    Composition features of carbon and oxygen isotopes in marine carbonate rocks of Cambrian-Ordovician in Bachu area of Tarim Basin were researched. Factors influencing the variation of carbon isotope were analysed. The results show that the variation of {delta}{sup 13}C of the Cambrian-Ordovician marine carbonate rocks is closely related to the changes of sea level. The slower organic carbon burial during sea level fall from the Early Cambrian to Middle Cambrian led to a decrease of the {delta}{sup 13}C value of carbonate rocks of this stage. The rise of organic productivity together with a rapid burial of organic carbon during the rise of sea level in Early Ordivician led to an increase of the {delta}{sup 13}C value of carbonate rocks of this stage because of a high sulfate content in seawater in the Middle Cambrian, the reduction by sulfate bacteria caused an oxidation of organic matter, resulting in a decrease of the {delta}{sup 13} values. The negative {delta}{sup 13}C value in some samples may be related to the fractionation of CO{sub 2} emitted from magma activity or volcanism. 14 refs., 2 figs., 2 tabs.

  12. Rapid carbon-carbon bond formation and cleavage revealed by carbon isotope exchange between the carboxyl carbon and inorganic carbon in hydrothermal fluids

    Science.gov (United States)

    Glein, C. R.; Cody, G. D.

    2013-12-01

    The carbon isotopic composition of organic compounds in water-rock systems (e.g., hydrothermal vents, sedimentary basins, and carbonaceous meteorites) is generally interpreted in terms of the isotopic composition of the sources of such molecules, and the kinetic isotope effects of metabolic or abiotic reactions that generate or transform such molecules. This hinges on the expectation that the carbon isotopic composition of many organic compounds is conserved under geochemical conditions. This expectation is reasonable in light of the strength of carbon-carbon bonds (ca. 81 kcal/mol); in general, environmental conditions conducive to carbon-carbon bond cleavage typically lead to transformations of organic molecules (decarboxylation is a notable example). Geochemically relevant reactions that involve isotopic exchange between carbon atoms in organic molecules and inorganic forms of carbon with no change in molecular structure appear to be rare. Notwithstanding such rarity, there have been preliminary reports of relatively rapid carbon isotope exchange between the carboxyl group in carboxylic acids and carbon dioxide in hot water [1,2]. We have performed laboratory hydrothermal experiments to gain insights into the mechanism of this surprising reaction, using phenylacetate as a model structure. By mass spectrometry, we confirm that the carboxyl carbon undergoes facile isotopic exchange with 13C-labeled bicarbonate at moderate temperatures (i.e., 230 C). Detailed kinetic analysis reveals that the reaction rate is proportional to the concentrations of both reactants. Further experiments demonstrate that the exchange reaction only occurs if the carbon atom adjacent to the carboxyl carbon is bonded to a hydrogen atom. As an example, no carbon isotope exchange was observed for benzoate in experiments lasting up to one month. The requirement of an alpha C-H bond suggests that enolization (i.e., deprotonation of the H) is a critical step in the mechanism of the exchange

  13. LBA-ECO CD-08 Leaf Carbon, Nitrogen, LAI, and Isotope Data, Manaus, Brazil: 2001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides measurements for carbon (C), nitrogen (N), leaf area index (LAI), and carbon isotope ratio data (13C and 14C) of leaves sampled at the Manaus...

  14. LBA-ECO CD-08 Leaf Carbon, Nitrogen, LAI, and Isotope Data, Manaus, Brazil: 2001

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides measurements for carbon (C), nitrogen (N), leaf area index (LAI), and carbon isotope ratio data (13C and 14C) of leaves sampled at...

  15. Observation of large enhancements of charge exchange cross sections with neutron-rich carbon isotopes

    Science.gov (United States)

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

    2016-04-01

    Production cross sections of nitrogen isotopes from high-energy (˜ 950 MeV per nucleon) carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes (A = 12 to 19). The fragment separator FRS at GSI was used to deliver C-isotope beams. The cross sections of the production of N-isotopes were determined by charge measurements of forward-going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge-exchange (Cex) reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and/or Fermi transition strength at low excitation energies for neutron-rich carbon isotopes. It was also observed that the Cex cross sections were enhanced much more strongly for neutron-rich isotopes in the C-target data.

  16. Factors affecting the isotopic composition of organic matter. (1) Carbon isotopic composition of terrestrial plant materials.

    Science.gov (United States)

    Yeh, H W; Wang, W M

    2001-07-01

    The stable isotope composition of the light elements (i.e., H, C, N, O and S) of organic samples varies significantly and, for C, is also unique and distinct from that of inorganic carbon. This is the result of (1) the isotope composition of reactants, (2) the nature of the reactions leading to formation and post-formational modification of the samples, (3) the environmental conditions under which the reactions took place, and (4) the relative concentration of the reactants compared to that of the products (i.e., [products]/[reactants] ratio). This article will examine the carbon isotope composition of terrestrial plant materials and its relationship with the above factors. delta13C(PDB) values of terrestrial plants range approximately from -8 to -38%, inclusive of C3-plants (-22 to -38%), C4-plants (-8 to -15%) and CAM-plants (-13 to -30%). Thus, the delta13C(PDB) values largely reflect the photosynthesis pathways of a plant as well as the genetics (i.e., species difference), delta13C(PDB) values of source CO2, relevant humidity, CO2/O2 ratios, wind and light intensity etc. Significant variations in these values also exist among different tissues, different portions of a tissue and different compounds. This is mainly a consequence of metabolic reactions. Animals mainly inherit the delta13C(PDB) values of the foods they consume; therefore, their delta13C(PDB) values are similar. The delta13C(PDB) values of plant materials, thus, contain information regarding the inner workings of the plants, the environmental conditions under which they grow, the delta13C(PDB) values of CO2 sources etc., and are unique. Furthermore, this uniqueness is passed on to their derivative matter, such as animals, humus etc. Hence, they are very powerful tools in many areas of research, including the ecological and environmental sciences.

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

    Science.gov (United States)

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

    2011-11-01

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

  18. 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

  19. Carbon isotope variability in monosaccharides and lipids of aquatic algae and terrestrial plants

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Dongen, B.E. van; Schouten, S.

    2002-01-01

    The stable carbon-isotope compositions of individual monosaccharides and lipids, as well as the bulk stable carbon-isotope composition of total cell material from different aquatic and terrestrial plants were determined. With the exception of a Phaeocystis sp. bloom sample, monosaccharides were

  20. Quantification of the carbonaceous matter origin in submicron marine aerosol particles by dual carbon isotope analysis

    OpenAIRE

    D. Ceburnis; A. Garbaras; S. Szidat; M. Rinaldi; S. Fahrni; N. Perron; L. Wacker; S. Leinert; V. Remeikis; M. C. Facchini; A. S. H. Prevot; S. G. Jennings; C. D. O'Dowd

    2011-01-01

    Dual carbon isotope analysis has been performed for the first time demonstrating a potential in organic matter apportionment between three principal sources: marine, terrestrial (non-fossil) and fossil fuel due to unique isotopic signatures. The results presented here, utilising combinations of dual carbon isotope analysis, provides a conclusive evidence of a dominant biogenic organic fraction to organic aerosol over biologically active oceans. In particular, the NE Atlantic, which is...

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

    Science.gov (United States)

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

    1994-01-01

    The radiocarbon content and stable isotope composition of soil carbonate are best described by a dynamic system in which isotopic reequilibration occurs as a result of recurrent dissolution and reprecipitation. Depth of water penetration into the soil profile, as well as soil age, determines the degree of carbonate isotope reequilibration. We measured ??13C, ??18O and radiocarbon content of gravel rinds and fine (alluvial fans were deposited.

  2. Trace Metals, Rare Earths, Carbon and Pb Isotopes as Proxies of Environmental Catastrophe at the Permian - Triassic Boundary in Spiti Himalayas, India

    Science.gov (United States)

    Ghosh, N.; Basu, A. R.; Garzione, C. N.; Ghatak, A.; Bhargava, O. N.; Shukla, U. K.; Ahluwalia, A. D.

    2015-12-01

    Himalayan sediments from Spiti Valley, India preserve geochemical signatures of the Permian - Triassic (P-Tr) mass extinction in the Neo-Tethys Ocean. We integrate new sedimentological and fossil record with high-resolution geochemical-isotopic data from Spiti that reveals an ecological catastrophe of global proportions. Trace elements of U, Th, Nb, Ta, Zr, Hf, the rare earths (REE) and carbon, oxygen and lead isotopes measured across the P-Tr boundary in Spiti are used as proxies for evaluating abrupt changes in this continental shelf environment. δ13Corg excursions of 2.4‰ and 3.1‰ in Atargu and Guling P-Tr sections in Spiti Valley are associated with an abrupt fall of biological productivity while δ13Ccarb and δ18Ocarb record of these sediments shows effects of diagenesis. Here, the P-Tr boundary is compositionally distinct from the underlying Late Permian gray shales, as a partly gypsiferous ferruginous layer that allows additional geochemical-isotopic investigation of sedimentary sources. Conspicuous Ce - Eu anomalies in the light REE-enriched Late Permian shales reflect the source composition of the adjacent Panjal Trap basalts of Kashmir. An abrupt change of this source to continental crust is revealed by Nb - Ta and Zr - Hf anomalies at the P-Tr ferruginous layer and continuing through the overlying Early Triassic carbonate rocks. Pb concentration and isotope ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb identify changes in the sedimentary element flux, distinguishing the Late Permian shales from the distinct siliciclastic continental crustal signature in the Early Triassic carbonates. These geochemical-isotopic constraints on the sedimentary geochemistry of one of the most critical transitions in geological record establish the utility of multi-proxy datasets for paleoenvironmental reconstructions.

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

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

  4. Effects of decalcification on bulk and compound-specific nitrogen and carbon isotope analyses of dentin.

    Science.gov (United States)

    Brault, Emily K; Koch, Paul L; Gier, Elizabeth; Ruiz-Cooley, R I; Zupcic, Jessica; Gilbert, Kwasi N; McCarthy, Matthew D

    2014-12-30

    For bulk carbon and nitrogen isotope analysis of dentin, samples are typically decalcified. Since the non-protein carbon in dentin is low, whole sample analysis may produce reliable data. Compound-specific isotope analysis (CSIA) of bone and tooth dentin protein is a powerful tool for reconstructing the flow of carbon and nitrogen in modern and past food webs. Decalcification has also been used to prepare bone and dentin samples for CSIA, but the effects of this process on bulk dentin, amino acid composition, and their specific isotope values are not known. The bulk isotope values of raw and decalcified dentin from a sperm whale tooth were measured to determine the effects of decalcification and the accuracy of untreated dentin results. CSIA was also performed on decalcified and raw dentin to examine differences in the amino acid isotope values and molar composition between these two approaches. Analysis of raw dentin yields precise and accurate bulk isotope measurements for this animal. The isotopic values of decalcified samples and raw dentin for individual amino acids were similar, but the average of the isotope value offsets between the two sample types was significant. The presence of inorganic material complicated raw sample processing for individual amino acid isotope values, and may have contributed to the isotopic differences between decalcified and raw samples. Decalcification is not needed to measure bulk isotope values in dentin from this modern odontocete, probably because the lipid and carbonate concentrations are low and the carbon isotope values of dentin protein and carbonate are similar. This method should not be applied in some cases (e.g., with fossil dentin and modern bone). Decalcification should still be used prior to CSIA since significant matrix issues occur with raw dentin processing and decalcification does not alter the amino acid molar composition or isotopic values of dentin. Copyright © 2014 John Wiley & Sons, Ltd.

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

    Science.gov (United States)

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

    2010-12-01

    Climate, biome, and plant community are important predictors of carbon isotope patterns recorded in leaves and leaf waxes. However, signatures recorded by terrestrial organic carbon and lipids that have mixed floral sources (e.g., n-alkanes) potentially reflect both plant community changes and climate. More taxonomically specific proxies for plants (i.e., di- and tri-terpenoids for conifers and angiosperms, respectively), can help to resolve the relative influences of changing community and climate, provided differences in biomarker production and lipid biosynthetic fractionation among plants can be better constrained. We present biomarker abundance and carbon isotope values for lipids from leaves, branches and bark of 44 tree species, representing 21 families including deciduous and evergreen conifers and angiosperms. n-alkane production differs greatly between conifer and angiosperm leaves. Both deciduous and evergreen angiosperms make significantly more n-alkanes than conifers, with n-alkanes not detected in over half of the conifers in our study. Terpenoid abundances scale strongly with leaf habit: evergreen species have significantly higher abundances. We combine these relative differences in lipid production with published estimates of fluxes for leaf litter from conifer and angiosperm trees to develop a new proxy approach for estimating paleo plant community inputs to ancient soils and sediments. To test our modern calibration results, we have evaluated n-alkanes and terpenoids from laterally extensive (~18 km) carbonaceous shales and mudstones in Eocene sediments (52.6 Ma) at Fifteenmile Creek in the Bighorn Basin (WY, USA). Our terpenoid-based proxy predicts on average a 40% conifer community, which is remarkably close in agreement with a fossil-based estimate of 36%. n-alkane carbon isotope fractionation (leaf-lipid) differs among plant types, with conifer n-alkanes about 2-3‰ 13C enriched relative to those in angiosperms. Since conifer leaves are

  6. 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

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

    Science.gov (United States)

    Daniel H. Doctor; Carol Kendall; Stephen D. Sebestyen; James B. Shanley; Nobuhito Ohte; Elizabeth W. Boyer

    2008-01-01

    The stable isotopic composition of dissolved inorganic carbon (δ13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed δ13C-DIC increased between 3-5% from the stream source to the outlet weir...

  8. Determination of the carbon kinetic isotope effects on propane hydroxylation mediated by the methane monooxygenases from Methylococcus capsulatus (Bath) by using stable carbon isotopic analysis.

    Science.gov (United States)

    Huang, Ded-Shih; Wu, Suh-Huey; Wang, Yane-Shih; Yu, Steve S-F; Chan, Sunney I

    2002-08-02

    Authentic propane with known position-specific carbon isotope composition at each carbon atom was subjected to hydroxylation by the particulate and soluble methane monooxygenase (pMMO and sMMO) from Methylococcus capsulatus (Bath), and the corresponding position-specific carbon isotope content was redetermined for the product 2-propanol. Neither the reaction mediated by pMMO nor that with sMMO showed an intermolecular (12)C/(13)C kinetic isotope effect effect on the propane hydroxylation at the secondary carbon; this indicates that there is little structural change at the carbon center attacked during formation of the transition state in the rate-determining step. This finding is in line with the concerted mechanism proposed for pMMO (Bath), and suggested for sMMO (Bath), namely, direct side-on insertion of an active "O" species across the C-H bond, as has been previously reported for singlet carbene insertion.

  9. The magnesium isotope record of cave carbonate archives

    Directory of Open Access Journals (Sweden)

    S. Riechelmann

    2012-11-01

    Full Text Available Here we explore the potential of magnesium (δ26Mg isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco, the warm-temperate (Germany, the equatorial-humid (Peru and the cold-humid (Austria climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the δ26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ26Mg values (GDA: −4.26 ± 0.07‰ and HK3: −4.17 ± 0.15‰, and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B δ26Mg: −3.96 ± 0.04‰ but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ26Mg: −4.01 ± 0.07‰; BU 4 mean δ26Mg: −4.20 ± 0.10‰ suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: −3.00 ± 0.73‰; SPA 59: −3.70 ± 0.43‰ are affected by glacial versus interglacial climate change with outside air temperature

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

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, Sergey S.

    2014-11-01

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ{sup 13}C, δ{sup 18}O and Δ{sup 17}O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated {sup 13}CO/{sup 12}CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in {sup 13}C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH{sub 4}) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH{sub 4} to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in {sup 13}C, were found significant

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

    Science.gov (United States)

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

    2016-01-01

    Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ18O and δ13C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75–200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ18O and δ13C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a ‘vital effect’ or a higher calcification rate. An interesting pattern of increase in the δ13C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ13C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude. PMID:26903274

  12. Carbon isotopic fractionation during biodegradation of phthalate esters in anoxic condition.

    Science.gov (United States)

    Liu, Hui; Wu, Zhen; Huang, Xianyu; Yarnes, Chris; Li, Minjing; Tong, Lei

    2015-11-01

    Here we evaluate the quantitative relationship between carbon isotopic fractionation and anoxic biodegradation of phthalate esters (PAEs), a kind of endocrine disruptors. The stable carbon isotope delta values (δ(13)C) of 4 PAEs, i.e. di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-n-butyl phthalate (DBP), and di-iso-butyl phthalate (DiBP), were analyzed during biodegradation by a pure bacteria strain isolated from the shallow aquifer sediment in anoxic condition. Results showed that the carbon isotopic fractionation in the initial degradation of PAEs was well-described by the Rayleigh equation model with R(2) from 0.8885 to 0.9821. The carbon isotopic fractionation (ε) for DMP and DEP were -4.6±0.4‰ and -2.9±0.1‰, respectively, while DBP and DiBP showed limited isotopic fractionation. A linear relationship between ε values and the total carbon atoms present in straight-carbon-chain PAE molecules with R(2) of 0.9918. The apparent kinetic isotope effects (AKIEs) were calculated for proposed 4 initial transformation pathways of PAEs. The high carbon AKIEs of 1.048 and 1.036 were obtained for single enzymatic hydrolysis of DMP and DEP, respectively, and fell in the expected KIE range of 1.03-1.09. However, the intrinsic carbon isotope effects for enzymatic hydrolysis of DBP and DiBP might be masked. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Isotope studies of carbonate rocks of La Luna Formation (Venezuela) to constrain the oceanic anoxic event 3 (OAE3)

    Science.gov (United States)

    Machado, M. C.; Chemale, F., Jr.; Kawashita, K.; Rey, O.; Moura, C. A. V.

    2016-12-01

    87Sr/86Sr ratios, δ13C, and δ18O determinations performed on 30 bulk carbonate rocks are presented to constrain the isotope characteristics regarding Oceanic Anoxic Event 3 in the La Luna Formation, Maracaibo Basin. The samples were collected along a 22 m profile in San Miguel region (Merida State, Venezuela). The exhibited 87Sr/86Sr ratios are between 0.707659, at the base, and 0.707733 at the top of studied section, corresponding estimated younger numerical ages than the inferred ages dated as Santonian (85.8-83.5 Ma) based on occurrence of Dicarinella asymetrica. The obtained 87Sr/86Sr ratios are certainly higher than expected for Santonian sea Sr and they are attributed to regular riverine strontium fluxes in the restricted (gulf-like) Maracaibo Basin. The values of δ18O data between -3.76‰ and -11.76‰ are distributed in two distinct clusters in a same way and coherent as for δ13C data which are in a range between -1.75‰ and -13.87‰. One of the clusters δ13C = -2.5 ± 1.0‰ and δ18O = -10.0 ± 1.5‰), illustrate the homogeneous marine deposition under tropical conditions, while the other, more variable, probably could reflect the cyclicity of temporally changes in Pacific versus Atlantic Ocean circulation with cooling water or cooling trend climate. These δ13C values around -2.5 ± 1.0‰ do not fit with the significant carbon isotope excursion as expected for the oceanic anoxic event (OAE) and support the work hypothesis that Coniacian-Santonian anoxic event (denominate as OAE3) is not a global one.

  14. 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

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

    Science.gov (United States)

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

    2017-08-01

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

  16. Isotopic resolution of carbon monoxide and carbon dioxide by NIR diode laser spectroscopy

    OpenAIRE

    Lau, Steffen; Salffner, Katharina; Löhmannsröben, Hans-Gerd

    2006-01-01

    Near-infrared (NIR) absorption spectroscopy with tunable diode lasers allows the simultaneous detection of the three most important isotopologues of carbon dioxide (12CO2, 13CO2, 12C18O16O) and carbon monoxide (12CO, 13CO, 12C18O). The flexible and compact fiber-optic tunable diode laser absorption spectrometer (TDLAS) allows selective measurements of CO2 and CO with high isotopic resolution without sample preparation since there is no interference with water vapour. For each species, linear ...

  17. Carbon isotope signature of dissolved inorganic carbon (DIC) in precipitation and atmospheric CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gorka, Maciej [Laboratory of Isotope Geology and Geoecology, Department of Applied Geology and Geochemistry, Institute of Geological Sciences, University of Wroclaw, Cybulskiego Street 30, 50-205 Wroclaw (Poland); Sauer, Peter E. [Biogeochemical Laboratory, Department of Geological Sciences, Indiana University (United States); Lewicka-Szczebak, Dominika, E-mail: dominika.lewicka@ing.uni.wroc.p [Laboratory of Isotope Geology and Geoecology, Department of Applied Geology and Geochemistry, Institute of Geological Sciences, University of Wroclaw, Cybulskiego Street 30, 50-205 Wroclaw (Poland); Jedrysek, Mariusz-Orion [Laboratory of Isotope Geology and Geoecology, Department of Applied Geology and Geochemistry, Institute of Geological Sciences, University of Wroclaw, Cybulskiego Street 30, 50-205 Wroclaw (Poland)

    2011-01-15

    This paper describes results of chemical and isotopic analysis of inorganic carbon species in the atmosphere and precipitation for the calendar year 2008 in Wroclaw (SW Poland). Atmospheric air samples (collected weekly) and rainwater samples (collected after rain episodes) were analysed for CO{sub 2} and dissolved inorganic carbon (DIC) concentrations and for {delta}{sup 13}C composition. The values obtained varied in the ranges: atmospheric CO{sub 2}: 337-448 ppm; {delta}{sup 13}C{sub CO2} from -14.4 to -8.4 per mille ; DIC in precipitation: 0.6-5.5 mg dm{sup -3}; {delta}{sup 13}C{sub DIC} from -22.2 to +0.2 per mille . No statistical correlation was observed between the concentration and {delta}{sup 13}C value of atmospheric CO{sub 2} and DIC in precipitation. These observations contradict the commonly held assumption that atmospheric CO{sub 2} controls the DIC in precipitation. We infer that DIC is generated in ambient air temperatures, but from other sources than the measured atmospheric CO{sub 2}. The calculated isotopic composition of a hypothetical CO{sub 2} source for DIC forming ranges from -31.4 to -11.0 per mille , showing significant seasonal variations accordingly to changing anthropogenic impact and atmospheric mixing processes. - Carbon isotopic composition of DIC in precipitation is not in equilibrium with atmospheric CO{sub 2} in an urban area.

  18. 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.

  19. Tracing carbonate-silicate interaction during subduction using magnesium and oxygen isotopes.

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    Wang, Shui-Jiong; Teng, Fang-Zhen; Li, Shu-Guang

    2014-11-04

    Subduction of carbonates and carbonated eclogites into the mantle plays an important role in transporting carbon into deep Earth. However, to what degree isotopic exchanges occur between carbonate and silicate during subduction remains unclear. Here we report Mg and O isotopic compositions for ultrahigh pressure metamorphic marbles and enclosed carbonated eclogites from China. These marbles include both calcite- and dolomite-rich examples and display similar O but distinct Mg isotopic signatures to their protoliths. Their δ(26)Mg values vary from -2.508 to -0.531‰, and negatively correlate with MgO/CaO ratios, unforeseen in sedimentary carbonates. Carbonated eclogites have extremely heavy δ(18)O (up to +21.1‰) and light δ(26)Mg values (down to -1.928‰ in garnet and -0.980‰ in pyroxene) compared with their protoliths. These unique Mg-O isotopic characteristics reflect differential isotopic exchange between eclogites and carbonates during subduction, making coupled Mg and O isotopic studies potential tools for tracing deep carbon recycling.

  20. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter

    Science.gov (United States)

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-06-01

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to 12C to enrich in the released CO2 while 13C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance.

  1. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter.

    Science.gov (United States)

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-06-09

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to (12)C to enrich in the released CO2 while (13)C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance.

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

  4. Uncovering the Neoproterozoic carbon cycle.

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    Johnston, D T; Macdonald, F A; Gill, B C; Hoffman, P F; Schrag, D P

    2012-02-29

    Interpretations of major climatic and biological events in Earth history are, in large part, derived from the stable carbon isotope records of carbonate rocks and sedimentary organic matter. Neoproterozoic carbonate records contain unusual and large negative isotopic anomalies within long periods (10-100 million years) characterized by δ(13)C in carbonate (δ(13)C(carb)) enriched to more than +5 per mil. Classically, δ(13)C(carb) is interpreted as a metric of the relative fraction of carbon buried as organic matter in marine sediments, which can be linked to oxygen accumulation through the stoichiometry of primary production. If a change in the isotopic composition of marine dissolved inorganic carbon is responsible for these excursions, it is expected that records of δ(13)C(carb) and δ(13)C in organic carbon (δ(13)C(org)) will covary, offset by the fractionation imparted by primary production. The documentation of several Neoproterozoic δ(13)C(carb) excursions that are decoupled from δ(13)C(org), however, indicates that other mechanisms may account for these excursions. Here we present δ(13)C data from Mongolia, northwest Canada and Namibia that capture multiple large-amplitude (over 10 per mil) negative carbon isotope anomalies, and use these data in a new quantitative mixing model to examine the behaviour of the Neoproterozoic carbon cycle. We find that carbonate and organic carbon isotope data from Mongolia and Canada are tightly coupled through multiple δ(13)C(carb) excursions, quantitatively ruling out previously suggested alternative explanations, such as diagenesis or the presence and terminal oxidation of a large marine dissolved organic carbon reservoir. Our data from Namibia, which do not record isotopic covariance, can be explained by simple mixing with a detrital flux of organic matter. We thus interpret δ(13)C(carb) anomalies as recording a primary perturbation to the surface carbon cycle. This interpretation requires the revisiting of

  5. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    Science.gov (United States)

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

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

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

    Science.gov (United States)

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

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in δ(13)C-L and δ(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between δ(13)C-L and δ(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Measuring Carbon and Oxygen Isotope Uptake into Inorganic Calcite using Crystal Growth Experiments

    Science.gov (United States)

    Baker, E. B.; Watkins, J. M.

    2014-12-01

    Carbon and oxygen isotopes measured on natural calcite crystals provide a record of paleo-environment conditions. Despite the importance of measuring stable isotopes in calcite for paleo-environment reconstructions, there is neither a general theory nor an experimental data set that fully separates the effects of pH, temperature, and precipitation rate on isotope discrimination during calcite growth. Many stable isotope studies of calcite have focused on either carbon or oxygen isotope compositions individually, but few have measured both carbon and oxygen isotope uptake in the same set of crystals. We are precipitating inorganic calcite across a range in temperature, pH, and precipitation rate to guide the development of a general theory for combined carbon and oxygen isotope uptake into calcite crystals grown on laboratory timescales. In our experiments, dissolved inorganic carbon (DIC) is added to an aqueous solution (15 mM CaCl2 + 5 mM NH4Cl) by CO2 bubbling. Once a critical supersaturation is reached, calcite crystals nucleate spontaneously and grow on the beaker walls. A key aspect of this experimental approach is that the δ13C of DIC is relatively constant throughout the crystal growth period, because there is a continuous supply of DIC from the CO2-bearing bubbles. Carbonic anhydrase, an enzyme promoting rapid equilibration of isotopes between DIC and water, was added to ensure that the solution remained isotopically equilibrated during calcite growth. We have conducted experiments at T = 25°C and pH = 8.3 - 9.0. We observe that the fractionation of oxygen isotopes between calcite and water decreases with increasing pH, consistent with available data from experiments in which the enzyme carbonic anhydrase was used. Our results for carbon isotopes extend the available data set, which previously ranged from pH 6.62 to 7.75, to higher pH. At pH 8.3, we observe that calcite is isotopically heavier than DIC with respect to carbon isotopes by about 0.25‰. At

  8. Equations for lipid normalization of carbon stable isotope ratios in aquatic bird eggs.

    Directory of Open Access Journals (Sweden)

    Kyle H Elliott

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

  9. Reconstructing Late Ordovician carbon cycle variations

    Science.gov (United States)

    Pancost, Richard D.; Freeman, Katherine H.; Herrmann, Achim D.; Patzkowsky, Mark E.; Ainsaar, Leho; Martma, Tõnu

    2013-03-01

    The role of carbon dioxide in regulating climate during the early Paleozoic, when severe glaciations occurred during a putative greenhouse world, remains unclear. Here, we present the first molecular carbon isotope proxy-based estimates for Late Ordovician (early Katian) pCO2 levels, and explore the limitations of applying this approach to the reconstruction of Paleozoic pCO2. Carbon isotope profiles from three sites in Laurentia (Iowa, Ontario and Pennsylvania) and one site in Baltica (Estonia) exhibit overall low isotope fractionation between organic and inorganic carbon during photosynthesis (ɛp) and these values declined during the early Katian carbonate carbon isotope excursion (or Guttenberg Carbon Isotope Excursion, GICE). Algal ɛp values are sensitive to changes in CO2 concentrations, algae cell morphologies, and cell growth rates. To constrain these factors, we present molecular evidence that a decrease in the relative abundance of cyanobacteria and a change in the eukaryotic algae community co-occurred with the GICE. Regardless of local biotic or oceanographic influences, a decline in ɛp values indicates photosynthesis was sensitive to carbon concentrations, and via analogy with modern taxa, constrains pCO2 to below ˜8× pre-industrial levels (PIL), or about half of previous estimates. In addition, the global, positive carbon isotope excursions expressed in a wide variety of sedimentary materials (carbonate, bulk organic matter, n-alkanes, acyclic and cyclic isoprenoid hydrocarbons), provide compelling evidence for perturbation of the global carbon cycle, and this was likely associated with a decrease in pCO2 approximately 10 million years prior to the Hirnantian glaciations. Isotopic records from deeper water settings suggest a complex interplay of carbon sources and sinks, with pCO2 increasing prior to and during the early stages of the GICE and then decreasing when organic carbon burial outpaced increased volcanic inputs.

  10. 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.

  11. 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.

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

    Science.gov (United States)

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

    1987-01-01

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

  13. Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

    Science.gov (United States)

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

    2012-01-01

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

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

    Science.gov (United States)

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

    2013-06-01

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

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

    Science.gov (United States)

    Tomita, Hideki; Watanabe, Kenichi; Takiguchi, Yu; Kawarabayashi, Jun; Iguchi, Tetsuo

    In decommissioning process of nuclear facilities, large amount of radioactive isotopes are discharged as waste. Radioactive carbon isotope (14C) is one of the key nuclides to determine the upper limit of concentration in the waste disposal. In particular, 14C on the graphite reactor decommissioning should be separated from stable carbon isotopes (12C and 13C) and monitored for the public health and safety. We propose an isotope analysis system based on cavity ring-down laser spectroscopy (CRDS) to monitor the carbon isotopes (12C, 13C and 14C) in the isotope separation process for the graphite reactor decommissioning. This system is compact and suitable for a continuous monitoring, because the concentration of molecules including the carbon isotope is derived from its photo absorbance with ultra high sensitive laser absorption spectroscopy. Here are presented the necessary conditions of CRDS system for 14C isotope analysis through the preliminary experimental results of 13C isotope analysis with a prototype system.

  16. Fractionation of the stable isotopes of inorganic carbon by seagrasses.

    Science.gov (United States)

    Benedict, C R; Wong, W W; Wong, J H

    1980-03-01

    The delta(13)C values for seagrasses collected along the Texas Gulf Coast range from -10.9 to -11.4 per thousand. These values are similar to the delta(13)C values of terrestrial C(4) plants, but seagrasses lack bundle sheath cells which are important in determining the delta(13)C values of C(4) plants. This work attempts to explain the reason the delta(13)C values of seagrasses resemble the delta(13)C values of C(4) plants.Investigations on the photosynthetic characteristics of seagrasses show that dissolved CO(2) is the species of inorganic carbon absorbed or accumulated by Thalassia testudinum. The rate of photosynthetic CO(2) fixation varies from 9.6 to 129.0 micromoles CO(2) per milligram chlorophyll per hour in the presence of 0.042 to 1.9 millimolar dissolved CO(2) due to the high resistances of Thalassia leaves to CO(2) diffusion. Phosphoglyceric acid is the first stable product of photosynthetic CO(2) fixation in Thalassia which is a Calvin cycle plant. The light/dark ratios of (14)CO(2) release from submerged Thalassia leaf sections at 1, 21, and 100% O(2) indicate a small apparent photorespiration. Dark respiration continues in the light and is stimulated by 21 and 100% O(2). The low apparent photorespiration may be due to membrane and H(2)O resistances to CO(2) diffusion with subsequent refixation of the photorespired CO(2). The internal pool of CO(2) is not in equilibrium with the external pool of CO(2) which results in a closed system in the seagrasses.The delta(13)C value of CO(2) in sea H(2)O in isotopic equilibrium with HCO(3) (-) is -10.3 per thousand and the delta(13)C value of hexoses isolated from the leaves of Thalassia is -11.5 per thousand. In the closed system of the seagrasses there is a -1.2 per thousand fractionation of CO(2) by ribulose-1,5-bisphosphate carboxylase and the Calvin cycle. This contrasts to a fractionation of about -17 to -27 per thousand of the stable carbon isotopes of CO(2) by the Calvin cycle in the open system of

  17. 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

  18. Rate-dependent carbon and nitrogen kinetic isotope fractionation in hydrolysis of isoproturon.

    Science.gov (United States)

    Penning, Holger; Cramer, Christopher J; Elsner, Martin

    2008-11-01

    Stable isotope fractionation permits quantifying contaminant degradation in the field when the transformation reaction is associated with a consistent isotope enrichment factor epsilon. When interpreted in conjunction with dual isotope plots, isotope fractionation is also particularly useful for elucidating reaction mechanisms. To assess the consistency of epsilon and dual isotope slopes in a two-step reaction, we investigated the abiotic hydrolysis of the herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) using a fragmentation method that allows measuring isotope ratios in different parts of the molecule. Carbon and nitrogen position-specific isotope fractionation, as well as slopes in dual isotope plots, varied linearly with rate constants k(obs) depending on the presence of buffers that mediate the initial zwitterion formation. The correlation can be explained by two consecutive reaction steps (zwitterion formation followed by dimethylamine elimination) each of which has a different kinetic isotope effect and may be rate-limiting. Intrinsic isotope effects for both steps, extracted from our kinetic data using a novel theoretical treatment, agree well with values computed from density functional calculations. Our study therefore demonstrates that more variable isotope fractionation may be observed in simple chemical reactions than commonly thought, but that consistent epsilon or dual isotope slopes may nonetheless be encountered in certain molecular fragments.

  19. A sorghum (Sorghum bicolor mutant with altered carbon isotope ratio.

    Directory of Open Access Journals (Sweden)

    Govinda Rizal

    Full Text Available Recent efforts to engineer C4 photosynthetic traits into C3 plants such as rice demand an understanding of the genetic elements that enable C4 plants to outperform C3 plants. As a part of the C4 Rice Consortium's efforts to identify genes needed to support C4 photosynthesis, EMS mutagenized sorghum populations were generated and screened to identify genes that cause a loss of C4 function. Stable carbon isotope ratio (δ13C of leaf dry matter has been used to distinguishspecies with C3 and C4 photosynthetic pathways. Here, we report the identification of a sorghum (Sorghum bicolor mutant with a low δ13C characteristic. A mutant (named Mut33 with a pale phenotype and stunted growth was identified from an EMS treated sorghum M2 population. The stable carbon isotope analysis of the mutants showed a decrease of 13C uptake capacity. The noise of random mutation was reduced by crossing the mutant and its wildtype (WT. The back-cross (BC1F1 progenies were like the WT parent in terms of 13C values and plant phenotypes. All the BC1F2 plants with low δ13C died before they produced their 6th leaf. Gas exchange measurements of the low δ13C sorghum mutants showed a higher CO2 compensation point (25.24 μmol CO2.mol-1air and the maximum rate of photosynthesis was less than 5μmol.m-2.s-1. To identify the genetic determinant of this trait, four DNA pools were isolated; two each from normal and low δ13C BC1F2 mutant plants. These were sequenced using an Illumina platform. Comparison of allele frequency of the single nucleotide polymorphisms (SNPs between the pools with contrasting phenotype showed that a locus in Chromosome 10 between 57,941,104 and 59,985,708 bps had an allele frequency of 1. There were 211 mutations and 37 genes in the locus, out of which mutations in 9 genes showed non-synonymous changes. This finding is expected to contribute to future research on the identification of the causal factor differentiating C4 from C3 species that can be used

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

    NARCIS (Netherlands)

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

    2006-01-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

  2. Carbon isotope stratigraphy of an ancient (Ordovician) Bahamian-type carbonate platform: Implications for preservation of global seawater trends

    Science.gov (United States)

    Saltzman, M.; Leslie, S. A.; Edwards, C. T.; Diamond, C. W.; Trigg, C. R.; Sedlacek, A. R.

    2013-12-01

    Carbon isotope stratigraphy has a unique role in the interpretation of Earth history as one of the few geochemical proxies that have been widely applied throughout the geologic time scale, from the Precambrian to the Recent, as both a global correlation tool and proxy for the carbon cycle. However, in addition to consideration of the role of diagenesis, numerous studies have raised awareness of the fact that C-isotope trends derived from ancient carbonate platforms may not be representative of dissolved inorganic carbon from a well-mixed global ocean reservoir. Furthermore, the larger carbon isotopic fractionation in the formation of aragonite versus calcite from seawater must be taken into account. All three of these variables (diagenesis, water mass residence time, % aragonite) may change in response to sea level, producing trends in C-isotopes on ancient carbonate platforms that are unrelated to the global carbon cycle. Global carbon cycle fluxes may also have a cause-effect relationship with sea level changes, further complicating interpretations of stratigraphic trends in carbon isotopes from ancient platform environments. Studies of C-isotopes in modern carbonate platform settings such as the Great Bahama Bank (GBB) provide important analogues in addressing whether or not ancient platforms are likely to preserve a record of carbon cycling in the global ocean. Swart et al. (2009) found that waters of the GBB had generally the same or elevated values (ranging from +0.5‰ to +2.5‰) compared to the global oceans, interpreted as reflecting differential photosynthetic fractionation and precipitation of calcium carbonate (which lowers pH and converts bicarbonate into 12-C enriched carbon dioxide, leaving residual bicarbonate heavier). Carbonate sediments of the GBB have elevated C-isotopes, not only because of the high C-isotope composition of the overlying waters, but also due to the greater fractionation associated with precipitation of aragonite versus calcite

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

    Science.gov (United States)

    Jung, Joon-Young; Oh, Min-Kyu

    2015-01-01

    Determination of fluxes by (13)C tracer experiments depends on monitoring the (13)C labeling pattern of metabolites during isotope experiments. In metabolome-based (13)C metabolic flux analysis, liquid chromatography combined with mass spectrometry or tandem mass spectrometry (LC/MS or LC/MS/MS, respectively) has been mainly used as an analytical platform for isotope pattern studies of central carbon metabolites. However, gas chromatography with mass spectrometry (GC/MS) has several advantages over LC/MS, such as high sensitivity, low cost, ease of operation, and availability of mass spectra databases for comparison. In this study, analysis of isotope pattern for central carbon metabolites using GC/MS was demonstrated. First, a proper set of mass ions for central carbon metabolites was selected based on carbon backbone information and structural isomers of mass fragment ions. A total of 34 mass fragment ions was selected and used for the quantification of 25 central carbon metabolites. Then, to quantify isotope fractions, a natural mass isotopomer library for selected mass fragment ions was constructed and subtracted from isotopomer mass spectra data. The results revealed a surprisingly high abundance of partially labeled (13)C intermediates, such as 56.4% of fructose 6-phosphate and 47.6% of dihydroxyacetone phosphate at isotopic steady state, which were generated in the pentose phosphate pathway. Finally, dynamic changes of isotope fragments of central metabolites were monitored with a U-(13)C glucose stimulus response experiment in Kluyveromyces marxianus. With a comprehensive study of isotope patterns of central carbon metabolites using GC/MS, 25 central carbon metabolites and their isotopic fractions were successfully quantified. Dynamic and precise acquisition of isotope pattern can then be used in combination with proper kinetic models to calculate metabolic fluxes. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    NARCIS (Netherlands)

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

    2008-01-01

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

  5. LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest canopy...

  6. LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest...

  7. Effects of smelter sulfur dioxide emissions: a spatiotemporal perspective using carbon isotopes in tree rings

    National Research Council Canada - National Science Library

    Savard, M M; Bégin, C; Parent, M; Smirnoff, A; Marion, J

    2004-01-01

    ... from the smelter to evaluate conditions prior to and during the periods of smelter operation. The carbon isotope results obtained from spruce tree rings at our test site reveal an unprecedented and abrupt shift...

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

    Science.gov (United States)

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

    2016-04-01

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

  9. 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...

  10. Orbital Signals in Carbon Isotopes: Phase Distortion as a Signature of the Carbon Cycle

    Science.gov (United States)

    Laurin, Jiří; Rąžek, Bohuslav; Giorgioni, Martino

    2017-11-01

    Isotopic mass balance models are employed here to study the response of carbon isotope composition (δ13C) of the ocean-atmosphere system to amplitude-modulated perturbations on Milankovitch time scales. We identify a systematic phase distortion, which is inherent to a leakage of power from the carrier precessional signal to the modulating eccentricity terms in the global carbon cycle. The origin is partly analogous to the simple cumulative effect in sinusoidal signals, reflecting the residence time of carbon in the ocean-atmosphere reservoir. The details of origin and practical implications are, however, different. In amplitude-modulated signals, the deformation is manifested as a lag of the 405 kyr eccentricity cycle behind amplitude modulation (AM) of the short ( 100 kyr) eccentricity cycle. Importantly, the phase of AM remains stable during the carbon cycle transfer, thus providing a reference framework against which to evaluate distortion of the 405 kyr term. The phase relationships can help to (1) identify depositional and diagenetic signatures in δ13C and (2) interpret the pathways of astronomical signal through the climate system. The approach is illustrated by case studies of Albian and Oligocene records using a new computational tool EPNOSE (Evaluation of Phase in uNcertain and nOisy SEries). Analogous phase distortions occur in other components of the carbon cycle including atmospheric CO2 levels; hence, to fully understand the causal relationships on astronomical time scales, paleoclimate models may need to incorporate realistic, amplitude-modulated insolation instead of monochromatic sinusoidal approximations. Finally, detection of the lagged δ13C response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.

  11. Factors Affecting the Clumped Isotope Signature of Dissolved Inorganic Carbon and Carbonate Minerals

    Science.gov (United States)

    Hill, P. S.; Tripati, A. K.; Schauble, E. A.

    2011-12-01

    18O/16O ratios[a] and 13C-18O bond ordering[b] in many natural and synthetic carbonate minerals may reflect the extent of isotopic equilibration of dissolved inorganic carbon (DIC) species, rather than the crystalline equilibrium. In the simplest case where transport and surface-reaction steps do not impart their own fractionations, the clumped isotope signature (Δ47: the enrichment in per mil of 13C18O16O above the amount expected for a random distribution of isotopes among all CO2 isotopologues) of a carbonate mineral precipitating from solution would preserve the temperature of DIC equilibration at the time of precipitation. We examine the consequences of (1) the time scale of DIC equilibration and (2) precipitation rate on Δ47 values of carbonate minerals, using electronic structure models of molecular clusters that approximate aqueous and crystalline chemical environments. Our use of cluster models for both the aqueous and the mineral phases of the clumped isotope system has the advantage of enabling us to compare aqueous and mineral systems with the same electronic structure methods, partially canceling systematic model errors. Fluid cluster models containing 21-32 water molecules are generated from periodic-boundary-condition molecular dynamics simulations. Mineral clusters are derived from measured crystal structures, with boundaries terminated by link atoms so as to retain Pauling bond strengths with severed distal lattice bonds[c]. Different combinations of density functional theory (DFT) methods and basis sets are compared. These studies, combined with concurrent controlled precipitation experiments, will add to our understanding of the extent of disequilibrium effects on clumping while providing a framework to include previous studies (such as the work of Guo et al. on the kinetic effects of CO2 dehydration and dehydroxyation and acid digestion[e]). [a] Zeebe, R.E. (2007) G3, 8, Q09002,; Zeebe, R.E. (1999) GCA 63, 2001-2007 [b] Tripati, A.K. et al

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

    Science.gov (United States)

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

    2016-09-01

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

  13. Paired carbon stable-isotope records for the Cenomanian Stage (100.5 -93.9 Ma): correlation tool and Late Cretaceous pCO2 record?

    Science.gov (United States)

    Jarvis, Ian; Gröcke, Darren; Laurin, Jiří; Selby, David; Roest-Ellis, Sascha; Miles, Andrew; Lignum, John; Gale, Andrew; Kennedy, Jim

    2016-04-01

    Carbon stable-isotope stratigraphy of marine carbonates (δ13Ccarb) provides remarkable insights into past variation in the global carbon cycle, and has become firmly established as a powerful global correlation tool. Continuous δ13Ccarb time series are becoming increasingly available for much of the geological record, including the Upper Cretaceous. However, our knowledge of stratigraphic variation in the carbon isotopic composition of sedimentary organic matter (δ13Corg) is much poorer, and is generally restricted to organic-rich sedimentary successions and/or key boundary intervals. Close coupling exists between the global isotopic composition of the reduced and oxidised carbon reservoirs on geological time scales, but the stratigraphic resolution of most long-term δ13Corg Mesozoic records is inadequate to identify leads and lags in the responses of the two reservoirs to carbon cycle perturbations. Cenomanian times (100.5-93.9 Ma) represent perhaps the best documented episode of eustatic rise in sea level in Earth history and the beginning of the Late Mesozoic thermal maximum, driving global expansion of epicontinental seas and the onset of widespread pelagic and hemipelagic carbonate deposition. Significant changes occurred in global stable-isotope records, including two prominent perturbations of the carbon cycle - the Mid-Cenomanian Event I (MCEI; ~96.5-96.2 Ma) and Oceanic Anoxic Event 2 (OAE2; ~94.5-93.8 Ma). OAE2, one of two truly global Cretaceous OAEs, was marked by the widespread deposition of black shales, and a global positive carbon stable-isotope excursion of 2.0 - 2.5‰ δ13Ccarb, and up to 7‰ in the sulphur-bound phytane biomarker. MCEI, by contrast, shows a new results from the English Chalk reference section at Folkestone, and correlate the carbon-isotope events between England, France, Germany and Italy. Comparison of the Vergons δ13Ccarb vs. δ13Corg profiles demonstrates similar medium-term stratigraphic variation, but significant

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

    Science.gov (United States)

    Shields, Graham A; Mills, Benjamin J W

    2017-04-25

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

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

    Science.gov (United States)

    Shields, Graham A.; Mills, Benjamin J. W.

    2017-04-01

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

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

    Science.gov (United States)

    Mills, Benjamin J. W.

    2017-01-01

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

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

    Science.gov (United States)

    We use measurements of the concentration and stable carbon isotopic ratio (D 13C) of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels and microbial carbon source. We found that intensive sugar cane cultivation leads to ...

  18. 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

  19. Assessing carbon and hydrogen isotopic fractionation of diesel fuel n-alkanes during progressive evaporation.

    Science.gov (United States)

    Muhammad, Syahidah A; Hayman, Alan R; Van Hale, Robert; Frew, Russell D

    2015-01-01

    Compound-specific isotope analysis offers potential for fingerprinting of diesel fuels, however, possible confounding effects of isotopic fractionation due to evaporation need to be assessed. This study measured the fractionation of the stable carbon and hydrogen isotopes in n-alkane compounds in neat diesel fuel during evaporation. Isotope ratios were measured using a continuous flow gas chromatograph/isotope ratio mass spectrometer. Diesel samples were progressively evaporated at 24 ± 2°C for 21 days. Increasing depletion of deuterium in nC12-nC17 alkanes in the remaining liquid with increasing carbon chain length was observed. Negligible carbon isotope fractionation was observed. Preferential vaporization was measured for the shorter chain n-alkanes and the trend decreased with increasing chain length. The decrease in δ(2) H values indicates the preferential vaporization of the isotopically heavier species consistent with available quantitative data for hydrocarbons. These results are most important in the application of stable isotope technology to forensic analysis of diesel. © 2014 American Academy of Forensic Sciences.

  20. Dynamics of the Neoproterozoic carbon cycle.

    Science.gov (United States)

    Rothman, Daniel H; Hayes, John M; Summons, Roger E

    2003-07-08

    The existence of unusually large fluctuations in the Neoproterozoic (1,000-543 million years ago) carbon-isotopic record implies strong perturbations to the Earth's carbon cycle. To analyze these fluctuations, we examine records of both the isotopic content of carbonate carbon and the fractionation between carbonate and marine organic carbon. Together, these are inconsistent with conventional, steady-state models of the carbon cycle. The records can be well understood, however, as deriving from the nonsteady dynamics of two reactive pools of carbon. The lack of a steady state is traced to an unusually large oceanic reservoir of organic carbon. We suggest that the most significant of the Neoproterozoic negative carbon-isotopic excursions resulted from increased remineralization of this reservoir. The terminal event, at the Proterozoic-Cambrian boundary, signals the final diminution of the reservoir, a process that was likely initiated by evolutionary innovations that increased export of organic matter to the deep sea.

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

  3. Carbon and chlorine isotope fractionation during Fenton-like degradation of trichloroethene.

    Science.gov (United States)

    Liu, Yunde; Gan, Yiqun; Zhou, Aiguo; Liu, Cunfu; Li, Xiaoqian; Yu, Tingting

    2014-07-01

    Dual isotope approach has been proposed as a viable tool for characterizing and assessing in situ contaminant transformation, however, little data is currently available on its applicability to chlorinated ethenes. This study determined carbon and chlorine isotope fractionation during Fenton-like degradation of trichloroethene (TCE). Carbon and chlorine isotope enrichment factors were εC=-2.9 ± 0.3‰ and εCl=-0.9 ± 0.1‰, respectively. An observed small secondary chlorine isotope effect (AKIECl=1.001) was consistent with an initial transformation by adding hydroxyl radicals (OH) to CC bonds without cleavage of CCl bonds. The relative change in carbon and chlorine isotope ratios (Δ=Δδ(13)C/Δδ(37)Cl) was calculated to be 3.1 ± 0.2, approximately equal to the ratio of chlorine and carbon isotope enrichment factors (εC/εCl=3.2). The similarity of the Δ (or εC/εCl) values between Fenton-like degradation and microbial reductive dechlorination of TCE was observed, indicating that application of solely dual isotope approach may be limited in distinguishing the two transformation pathways. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2014-12-01

    Recent field studies on major sources of the important greenhouse gas methane (CH4) indicate significant underestimation of methane release from fossil fuel industrial (FFI) and animal husbandry sources, among others. In addition, uncertainties still exist with respect to carbon dioxide (CO2) measurements, especially source fingerprinting. CO2 isotopic analysis provides a valuable in situ measurement approach to fingerprint CH4 and CO2as associated with combustion sources, leakage from geologic reservoirs, or biogenic sources. As a result, these measurements can characterize strong combustion source plumes, such as power plant emissions, and discriminate these emissions from other sources. As part of the COMEX (CO2 and MEthane eXperiment) campaign, a novel CO2 isotopic analyzer was installed and collected data aboard the CIRPAS Twin Otter aircraft. Developing methods to derive CH4 and CO2 budgets from remote sensing data is the goal of the summer 2014 COMEX campaign, which combines hyperspectral imaging (HSI) and non-imaging spectroscopy (NIS) with in situ airborne and surface data. COMEX leverages the synergy between high spatial resolution HSI and moderate spatial resolution NIS. The carbon dioxide isotope analyzer developed by Los Gatos Research (LGR) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures CO2 concentration as well as δ13C, δ18O, and δ17O from CO2 at natural abundance (100-3000 ppm). The laboratory accuracy is ±1.2 ppm (1σ) in CO2 from 370-1000 ppm, with a long-term (1000 s) precision of ±0.012 ppm. The long-term precision for both δ13C and δ18O is 0.04 ‰, and for δ17O is 0.06 ‰. The analyzer was field-tested as part of the COWGAS campaign, a pre-cursor campaign to COMEX in March 2014, where it successfully discriminated plumes related to combustion processes associated with

  5. [Metabolic isotopic effects of carbon and production process in cultivated plants in light of oscillatory concept for photosynthesis].

    Science.gov (United States)

    Ivlev, A A; Dubinskiĭ, A Iu; Pichuzhkin, V I

    2013-01-01

    Some perspectives on the use of stable carbon isotopes (13C/12C) in studying production processes are considered. It has been shown that the efficiency of the isotope technique depends on the adequacy of the chosen model. The model of isotope fractionation proposed based on the oscillatory concept of photosynthesis provides for more accurate and comprehensive description of the observed empirical correlations between the yield (bioproductivity) and carbon isotope composition in cereal cultures as compared with the widely used stationary model.

  6. 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.

  7. Allochthonous sources and dynamic cycling of ocean dissolved organic carbon revealed by carbon isotopes

    Science.gov (United States)

    Zigah, Prosper K.; McNichol, Ann P.; Xu, Li; Johnson, Carl; Santinelli, Chiara; Karl, David M.; Repeta, Daniel J.

    2017-03-01

    We present concentration and isotopic profiles of total, size, and polarity fractionated dissolved organic carbon (DOC) from Station ALOHA (A Long-term Oligotrophic Habitat Assessment), an oligotrophic site in the North Pacific Ocean. The data show that, between the surface and 3500 m, low molecular weight (LMW) hydrophilic DOC, LMW hydrophobic DOC, and high molecular weight (HMW) DOC constitute 22-33%, 45-52%, and 23-35% of DOC, respectively. LMW hydrophilic DOC is more isotopically depleted (δ13C of -23.9‰ to -31.5‰ and Δ14C of -304‰ to -795‰; mean age of 2850 to 15000 years) than the LMW hydrophobic DOC (δ13C of -22‰ to -23‰ and Δ14C of -270‰ to -568‰; 2470 to 6680 years) and HMW DOC (δ13C of -21‰ and Δ14C of -24‰ to -294‰; 135-2700 years). Our analyses suggest that a large fraction of DOC may be derived from allochthonous sources such as terrestrial and hydrothermal DOC and cycle on much longer time scales of >10000 years or enter the ocean as preaged carbon.

  8. 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.

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

    Science.gov (United States)

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

    1992-01-01

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

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

    NARCIS (Netherlands)

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

    2005-01-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  12. Stable isotopes, ecological integration and environmental change: wolves record atmospheric carbon isotope trend better than tree rings.

    Science.gov (United States)

    Bump, Joseph K; Fox-Dobbs, Kena; Bada, Jeffrey L; Koch, Paul L; Peterson, Rolf O; Vucetich, John A

    2007-10-07

    Large-scale patterns of isotope ratios are detectable in the tissues of organisms, but the variability in these patterns often obscures detection of environmental trends. We show that plants and animals at lower trophic levels are relatively poor indicators of the temporal trend in atmospheric carbon isotope ratios (delta13C) when compared with animals at higher trophic levels. First, we tested how differences in atmospheric delta13C values were transferred across three trophic levels. Second, we compared contemporary delta13C trends (1961-2004) in atmospheric CO2 to delta13C patterns in a tree species (jack pine, Pinus banksiana), large herbivore (moose, Alces alces) and large carnivore (grey wolf, Canis lupus) from North America. Third, we compared palaeontological (approx. 30000 to 12000 14C years before present) atmospheric CO2 trends to delta13C patterns in a tree species (Pinus flexilis, Juniperus sp.), a megaherbivore (bison, Bison antiquus) and a large carnivore (dire wolf, Canis dirus) from the La Brea tar pits (southern California, USA) and Great Basin (western USA). Contrary to previous expectations, we found that the environmental isotope pattern is better represented with increasing trophic level. Our results indicate that museum specimens of large carnivores would best reflect large-scale spatial and temporal patterns of carbon isotopes in the palaeontological record because top predators can act as ecological integrators of environmental change.

  13. Carbon Isotope Evidence for the Stepwise Oxidation of the Proterozoic Environment

    Science.gov (United States)

    DesMarais, David J.; Strauss, Harald; Summons, Roger E.; Hayes, J. M.

    1992-01-01

    The oxidation of the Earth's crust and the increase in atmospheric oxygen early in Earth history have been linked to the accumulation of reduced carbon in sedimentary rocks. Trends in the carbon isotope composition of sedimentary organic carbon and carbonate show that during the Proterozoic aeon (2.5-0.54 Gyr ago) the organic carbon reservoir grew in size, relative to the carbonate reservoir. This increase, and the concomitant release of oxidizing power in the environment, occurred mostly during episodes of global rifting and orogeny.

  14. 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...

  15. Application of dual carbon-bromine isotope analysis for investigating abiotic transformations of tribromoneopentyl alcohol (TBNPA).

    Science.gov (United States)

    Kozell, Anna; Yecheskel, Yinon; Balaban, Noa; Dror, Ishai; Halicz, Ludwik; Ronen, Zeev; Gelman, Faina

    2015-04-07

    Many of polybrominated organic compounds, used as flame retardant additives, belong to the group of persistent organic pollutants. Compound-specific isotope analysis is one of the potential analytical tools for investigating their fate in the environment. However, the isotope effects associated with transformations of brominated organic compounds are still poorly explored. In the present study, we investigated carbon and bromine isotope fractionation during degradation of tribromoneopentyl alcohol (TBNPA), one of the widely used flame retardant additives, in three different chemical processes: transformation in aqueous alkaline solution (pH 8); reductive dehalogenation by zero-valent iron nanoparticles (nZVI) in anoxic conditions; oxidative degradation by H2O2 in the presence of CuO nanoparticles (nCuO). Two-dimensional carbon-bromine isotope plots (δ(13)C/Δ(81)Br) for each reaction gave different process-dependent isotope slopes (Λ(C/Br)): 25.2 ± 2.5 for alkaline hydrolysis (pH 8); 3.8 ± 0.5 for debromination in the presence of nZVI in anoxic conditions; ∞ in the case of catalytic oxidation by H2O2 with nCuO. The obtained isotope effects for both elements were generally in agreement with the values expected for the suggested reaction mechanisms. The results of the present study support further applications of dual carbon-bromine isotope analysis as a tool for identification of reaction pathway during transformations of brominated organic compounds in the environment.

  16. 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.

  17. Carbon and hydrogen isotope fractionation of benzene and toluene during hydrophobic sorption in multistep batch experiments.

    Science.gov (United States)

    Imfeld, G; Kopinke, F-D; Fischer, A; Richnow, H-H

    2014-07-01

    The application of compound-specific stable isotope analysis (CSIA) for evaluating degradation of organic pollutants in the field implies that other processes affecting pollutant concentration are minor with respect to isotope fractionation. Sorption is associated with minor isotope fractionation and pollutants may undergo successive sorption-desorption steps during their migration in aquifers. However, little is known about isotope fractionation of BTEX compounds after consecutive sorption steps. Here, we show that partitioning of benzene and toluene between water and organic sorbents (i.e. 1-octanol, dichloromethane, cyclohexane, hexanoic acid and Amberlite XAD-2) generally exhibits very small carbon and hydrogen isotope effects in multistep batch experiments. However, carbon and hydrogen isotope fractionation was observed for the benzene-octanol pair after several sorption steps (Δδ(13)C=1.6 ± 0.3‰ and Δδ(2)H=88 ± 3‰), yielding isotope fractionation factors of αC=1.0030 ± 0.0005 and αH=1.195 ± 0.026. Our results indicate that the cumulative effect of successive hydrophobic partitioning steps in an aquifer generally results in insignificant isotope fractionation for benzene and toluene. However, significant carbon and hydrogen isotope fractionation cannot be excluded for specific sorbate-sorbent pairs, such as sorbates with π-electrons and sorbents with OH-groups. Consequently, functional groups of sedimentary organic matter (SOM) may specifically interact with BTEX compounds migrating in an aquifer, thereby resulting in potentially relevant isotope fractionation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Oxygenation of the shallow ocean after the Great Oxidation Event: Geochemistry and Carbon isotopes of the Paleoproterozoic Hutuo Group in North China Craton

    Science.gov (United States)

    She, Z.; Yang, F.; Papineau, D.

    2013-12-01

    The Paleoproterozoic was known as a period of profound perturbations in marine environments and biogeochemical cycles due to the Great Oxidation Event (GOE), but the interconnections and consequences of these events remain poorly understood. We investigated the geochemistry and C isotopes of the 2.09-1.96 Ga Hutuo Group in the North China Craton (NCC) which provide evidence for the oxygenation of shallow oceans. The Hutuo Group is a >10-km-thick clastic and carbonate sequence with intercalated basalts and has undergone lower greenschist facies metamorphism. Diverse stromatolite morphotypes, ranging from small domical, conical, and columnar forms to bioherms with diameters up to 4 meters, as well as giant oncoids, are developed in the Hutuo carbonates. C isotopes of the Hutuo carbonates are characterized by a general decrease in δ13Ccarb values upsection. It consists of a lower part with δ13Ccarb ranging from 1.3 ‰ to 3.4 ‰, a middle part showing alternating positive and negative excursions of δ13Ccarb from -3.6 ‰ to 2.7 ‰, and a upper part of exclusively negative excursions with δ13Ccarb as light as -5.6 ‰. Most samples have δ18Ocarb greater than -10 ‰ and show no correlation between δ18Ocarb and δ13Ccarb. This, along with relatively low Mn/Sr ratios (mostly contamination by terrigenous materials provides constrains on the chemistry of the Paleoproterozoic ocean. PAAS-normalized REE patterns are flat or slightly LREE-depleted with variable but slightly negative to positive shale-normalized Ce anomaly and evident Eu anomaly. The carbonates have low concentrations of U, Mo, Co and Ni, and show upsection decrease in Mo, Co and Ni abundances, consistent with increasing redox states. Metapelites from the Hutuo Group show slightly positive Eu anomaly and low Mo concentrations and U/Th ratios (0.33 - 0.10), consistent with deposition in an oxygenated environment. Collectively, the data document the fluctuations of ocean redox states and final

  19. A simple stable carbon isotope method for investigating changes in the use of recent versus old carbon in oak.

    Science.gov (United States)

    McCarroll, Danny; Whitney, Matthew; Young, Giles H F; Loader, Neil J; Gagen, Mary H

    2017-08-01

    Stable carbon isotope ratios from early-wood (EW) and late-wood (LW) are used to test competing models of carbon storage and allocation, providing a cost-effective alternative to measuring and dating non-structural carbohydrates in mature temperate broad-leaf forest trees growing under natural conditions. Annual samples of EW and LW from seven mature oaks (Quercus robur L.) from Scotland, covering AD 1924-2012, were pooled, treated to isolate alpha-cellulose and pyrolysed to measure the carbon isotope ratios. Late-wood values are strongly correlated with summer temperature of the year of growth and EW contains the same signal offset by 1 year. After a warm summer, isotopic ratios of EW are similar to those of the preceding LW, but following cold summers they are relatively enriched. The results conflict with established models of isotopic variation within oak tree rings but support 'two-pool' models for storage of non-structural carbohydrates, with EW formation, which occurs prior to budburst, preferentially using young reserves accumulated in the previous summer. Under poor growing conditions trees access older reserves. Slight average isotopic enrichment of EW may be explained by preferential accumulation of reserves during warmer summers rather than by isotopic enrichment during starch formation in non-photosynthetic tissue. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

    Directory of Open Access Journals (Sweden)

    F. Keppler

    2004-01-01

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

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

    CERN Document Server

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

    2014-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2006-01-01

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

  3. Surface area dependence of calcium isotopic reequilibration in carbonates: Implications for isotopic signatures in the weathering zone

    Science.gov (United States)

    Fernandez, N. M.; Druhan, J. L.; Potrel, A.; Jacobson, A. D.

    2016-12-01

    The concept of dynamic equilibrium carries the implicit assumption of continued isotopic exchange between a mineral and the surrounding fluid. While this effect has received much attention in the marine paleoproxy literature, it has been relatively overlooked in application to the terrestrial environment. In weathering systems, a potential consequence is that rapid reequilibration may alter or erase isotopic signatures generated during secondary mineral formation. The extent and timescale over which isotopic signatures are reset in these hydrologic systems is unknown. Using reactive transport modeling, we show isotopic reequilibration under conditions reflecting terrestrial hydrologic settings to be significant and dependent on the reactive surface area of the solid. In particular, we suggest that the non-traditional stable isotopes commonly used in application to carbonates (e.g., Ca, Mg, Sr) are sensitive to these effects due to their rapid reaction rates. We aim to characterize the dependence of Ca isotopic reequilibration on surface area during calcite precipitation via batch experiments conducted at ambient temperature over 48-hour time periods. Calcite precipitation was performed in a closed batch reactor utilizing a controlled free-drift method. The batch reactors contained mixed supersaturated solutions of CaCl2 and NaHCO3 at an initial pH of 8.54. Precipitation was initiated by seed inoculation of calcite crystals with two distinct, pre-constrained surface areas. All experiments achieved the same final state of chemical equilibrium, but as expected, the fastest approach to equilibrium occurred for experiments employing calcite seeds with the highest surface area. This implies that differences in equilibrated Ca isotope ratios (δ44/40Ca) should reflect differences in surface area. This prediction is upheld by models of the experiments, indicating a measureable difference in δ44Ca during calcite precipitation where the higher surface area corresponds to

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

    Science.gov (United States)

    Saccon, M.; Kornilova, A.; Huang, L.; Moukhtar, S.; Rudolph, J.

    2015-09-01

    A method to quantify concentrations and stable carbon isotope ratios of secondary organic aerosols has been applied to study atmospheric nitrophenols in Toronto, Canada. The sampling of five nitrophenols, all with substantial secondary formation from the photooxidation of aromatic volatile organic compounds (VOCs), was conducted in the gas phase and particulate matter (PM) together and in PM alone. Their concentrations in the atmosphere are in the low ng m-3 range and, consequently, a large volume of air (> 1000 m3) is needed to analyze samples for stable carbon isotope ratios, resulting in sampling periods of typically 24 h. While this extended sampling period increases the representativeness of average values, it at the same time reduces possibilities to identify meteorological conditions or atmospheric pollution levels determining nitrophenol concentrations and isotope ratios. Average measured carbon isotope ratios of the different nitrophenols are between -34 and -33 ‰, which is well within the range predicted by mass balance. However, the observed carbon isotope ratios cover a range of nearly 9 ‰ and approximately 20 % of the isotope ratios of the products have isotope ratios lower than predicted from the kinetic isotope effect of the first step of the reaction mechanism and the isotope ratio of the precursor. This can be explained by isotope fractionation during reaction steps following the initial reaction of the precursor VOCs with the OH radical. Limited evidence for local production of nitrophenols is observed since sampling was done in the Toronto area, an urban center with significant anthropogenic emission sources. Strong evidence for significant local formation of nitrophenols is only found for samples collected in summer. On average, the difference in carbon isotope ratios between nitrophenols in the particle phase and in the gas phase is insignificant, but for a limited number of observations in summer, a substantial difference is observed. This

  5. Isotopes, ice ages, and terminal Proterozoic earth history

    Science.gov (United States)

    Kaufman, Alan J.; Knoll, Andrew H.; Narbonne, Guy M.

    1997-01-01

    Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals. PMID:11038552

  6. Isotopes, ice ages, and terminal Proterozoic earth history.

    Science.gov (United States)

    Kaufman, A J; Knoll, A H; Narbonne, G M

    1997-06-24

    Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals.

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

    Energy Technology Data Exchange (ETDEWEB)

    Miller, John B.; Tans, Pieter P.; Conway, Thomas J. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Climate Monitoring and Diagnostics Laboratory; White, James W.C.; Vaughn, Bruce W. [Univ. of Colorado, Boulder, CO (United States). Inst. for Arctic and Alpine Research

    2003-04-01

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

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

    Science.gov (United States)

    Wierzchnicki, Ryszard

    2013-04-01

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

  9. Quantification of petrogenic PAH in marine sediment using molecular stable carbon isotopic ratio measurement

    Energy Technology Data Exchange (ETDEWEB)

    Mazeas, L.; Budzinski, H. [Bordeaux-1 Univ., 33 - Talence (France). Laboratoire de Physico- et Toxico-Chimie des Systemes Naturels

    1999-04-01

    Compound-specific carbon isotope analyses were performed on polycyclic aromatic hydrocarbons (phenanthrene and methyl-phenanthrene) isolated from marine sediments contaminated with petroleum. Isotopic composition measurements of individual methyl-phenanthrene were subject to important uncertainties because they were not completely separated by gas chromatographic separation. Nevertheless the isotopic composition of the sum of methyl-phenanthrene was measured with good reproducibility. As petrogenic PAHs and PAHs present in the sediment before the petroleum contamination have different isotopic compositions it was possible to quantitatively source apportion methyl-phenanthrene in contaminated sediment with a good precision and reliability, using the isotopic composition of the sum of methyl-phenanthrene and a simple mass balance calculation. (authors) 10 refs.

  10. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    Science.gov (United States)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rügen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate

  11. Carbon and hydrogen isotopic compositions of algae and bacteria from hydrothermal environments, Yellowstone National Park

    Science.gov (United States)

    Estep, Marilyn L. F.

    1984-03-01

    Stromatolites forming today on a small scale in hydrothermal environments are chemical and biological analogues of much larger Precambrian formations. Carbon isotopic composition varied as a function of CO 2 concentration, pH, and species composition. Stratiform, layered stromatolites grew in silica-depositing springs at 55° to 70°C; they consisted mainly of a unicellular alga, Synechococcus, and a filamentous, photosynthetic bacterium, Chloroflexus. These thermophiles become enriched in 12C as the concentration of carbon dioxide in the effluent waters increases. At a concentration of 40 ppm total inorganic C, and δ 13C of organic carbon was ˜ -12%., whereas at 900 ppm total inorganic C, the δ 13C of similar species was ˜ -25%.. Conical stromatolites or conophytons (principally a filamentous, blue-green alga Phormidium and Chloroflexus) grew at 40°-55°C. In older, broader conophytons, Chloroflexus was the dominant organism. Their δ 13C values were ˜ -18%. in a variety of hot springs. In carbonate-depositing springs, i.e., carbon dioxide saturated, conophytons and stromatolites consisting of a variety of blue-green algae and photosynthetic bacteria had the most negative δ 13C values (to -30%.). These carbon isotope ratios are directly comparable to carbon isotope ratios of kerogen from Precambrian stromatolites. The presence and activity of methanogenic bacteria or heterotrophic, aerobic and anaerobic bacteria did not alter significantly the δ 13C of the original organic matter. The hydrogen isotopic fractionation between thermophilic organisms and water is 0 to -74 for temperatures of 85° to 46°C, respectively. Acidophilic algae fractionated hydrogen isotopes to a lesser extent than did the photosynthetic organisms inhabiting neutral pH springs. Because organic matter retains some of its original isotopic signature, relationships of CO 2 levels, pH, temperature, and species composition between modern stromatolites and their environment and those of

  12. 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.

  13. 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.

  14. Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC

    Directory of Open Access Journals (Sweden)

    D. R. Griffith

    2012-03-01

    Full Text Available Arctic warming is projected to continue throughout the coming century. Yet, our currently limited understanding of the Arctic Ocean carbon cycle hinders our ability to predict how changing conditions will affect local Arctic ecosystems, regional carbon budgets, and global climate. We present here the first set of concurrent, full-depth, dual-isotope profiles for dissolved inorganic carbon (DIC, dissolved organic carbon (DOC, and suspended particulate organic carbon (POCsusp at two sites in the Canada Basin of the Arctic Ocean. The carbon isotope composition of sinking and suspended POC in the Arctic contrasts strongly with open ocean Atlantic and Pacific sites, pointing to a combination of inputs to Arctic POCsusp at depth, including surface-derived organic carbon (OC, sorbed/advected OC, and OC derived from in situ DIC fixation. The latter process appears to be particularly important at intermediate depths, where mass balance calculations suggest that OC derived from in situ DIC fixation contributes up to 22% of POCsusp. As in other oceans, surface-derived OC is still a dominant source to Arctic POCsusp. Yet, we suggest that significantly smaller vertical POC fluxes in the Canada Basin make it possible to see evidence of DIC fixation in the POCsusp pool even at the bulk isotope level.

  15. Physics process of cosmogenic isotopes production on muons interactions with carbon target in liquid scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Zbiri, Karim; Martino, Jacques [Laboratoire Subatech, UMR6457: IN2P3/CNRS-universite-Ecole des Mines de Nantes, 4 rue A. Kastler, 44307 Nantes Cedex 03 (France)

    2006-07-15

    In the present paper we will focus on the problematic of cosmogenic isotopes, in particular Li-9 and He-8, which are produced by muons interactions with the carbon target contained in the liquid scintillator. The study of this kind of isotopes has a major role in reactor neutrino experiments because their ability to mimic the detection reaction. We will discuss the physics process which dominate the production of such isotopes, after we will show via comparisons with available data the reliability of this point of view. (authors)

  16. Sulphur and carbon isotopic composition of power supply coals in the Pannonian Basin, Hungary

    Energy Technology Data Exchange (ETDEWEB)

    Hamor-Vido, Maria [Eoetvoes Lorand Geophysical Institute of Hungary, H-1145 Budapest, Kolumbusz st. 17-23 (Hungary); Hamor, Tamas [Hungarian Geological Survey, H-1143 Budapest, Stefania st. 14 (Hungary)

    2007-08-01

    The present work is an attempt to establish the stable isotope database for Mesozoic to Tertiary coals from the Pannonian Basin, Hungary. Maceral composition, proximate analysis, sulphur form, sulphur isotopes (organic and pyritic), and carbon isotopes were determined. This database supports the assessment of the environmental risks associated with energy generation, the characterization of the formation and the distribution of sulphur in the coals used. The maceral composition, the sulphur composition, the C, S isotopic signatures, and some of the geological evidences published earlier show that the majority of these coals were deposited in freshwater and brackish water environments, despite the relatively high average sulphur content. However, the Upper Cretaceous, Eocene, and Lower Miocene formations also contain coal seams of marine origin, as indicated by their maceral composition and sulphur and carbon chemistry. The majority of the sulphur in these coals occurs in the organic form. All studied sulphur phases are relatively rich in {sup 34}S isotopes ({delta}{sup 34}S{sub organic} = + 12.74 permille, {delta}{sup 34}S{sub pyrite} = + 10.06 permille, on average). This indicates that marine bacterial sulphate reduction played a minor role in their formation, in the sense that isotopic fractionation was limited. It seems that the interstitial spaces of the peat closed rapidly during early diagenesis due to a regime of high depositional rate, leading to a relative enrichment of the heavy sulphur isotopes. (author)

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

    Science.gov (United States)

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

    2012-01-01

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

  18. Effect of competition on stable carbon isotope ratios of two tussock grass species.

    Science.gov (United States)

    Williams, K; Richards, J H; Caldwell, M M

    1991-09-01

    Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative δ 13 C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered.

  19. Nuclear Quantum Effects in the Layering and Diffusion of Hydrogen Isotopes in Carbon Nanotubes.

    Science.gov (United States)

    Kowalczyk, Piotr; Terzyk, Artur P; Gauden, Piotr A; Furmaniak, Sylwester; Kaneko, Katsumi; Miller, Thomas F

    2015-09-03

    Although recent experimental studies have demonstrated that H2 and D2 molecules wet the inner surface of supergrowth carbon nanotubes at low temperatures, characterization of the structural and dynamical properties in this regime is challenging. This Letter presents a theoretical study of self-diffusion in pure and binary H2, D2, and T2 contact monolayer films formed on the inner surface of a carbon nanotube. Our results show that monolayer formation and self-diffusion both in pure hydrogen isotopes and in H2/T2 and H2/D2 isotope mixtures is impacted by nuclear quantum effects, suggesting potential applications of carbon nanotubes for the separation of hydrogen isotopes.

  20. LBA-ECO CD-02 Carbon and Oxygen Isotopes in Atmospheric CO2 in the Amazon: 1999-2004

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set reports carbon and oxygen stable isotope ratios of atmospheric carbon dioxide (CO2) collected at several forest and pasture sites and in the...

  1. LBA-ECO CD-02 Carbon and Oxygen Isotopes in Atmospheric CO2 in the Amazon: 1999-2004

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set reports carbon and oxygen stable isotope ratios of atmospheric carbon dioxide (CO2) collected at several forest and pasture sites and in the free...

  2. Compound specific isotopic fractionation patterns suggest different carbon metabolisms among Chloroflexus-like bacteria in hot spring microbial mats

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Meer, M.T.J. van der; Schouten, S.; Leeuw, J.W. de; Ward, D.M.

    2003-01-01

    Stable carbon isotope fractionations between dissolved inorganic carbon and lipid biomarkers suggest photoautotrophy by Chloroflexus-like organisms in sulfidic and nonsulfidic Yellowstone hot springs. Where co-occurring, cyanobacteria appear to cross-feed Chloroflexus-like organisms supporting

  3. Fine root heterogeneity by branch order: exploring the discrepancy in root turnover estimates between minirhizotron and carbon isotopic methods

    Science.gov (United States)

    Dali Guo; Harbin Li; Robert J. Mitchell; Han Wenxuan; Joseph J. Hendricks; Timothy J. Fahey; Ronald L. Hendrick

    2008-01-01

    Fine roots constitute a large and dynamic component of the carbon cycles of terrestrial ecosystems. The reported fivefold discrepancy in turnover estimates between median longevity (ML) from minirhizotrons and mean residence time (MRT) using carbon isotopes may have global consequences.

  4. 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.

  5. 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.|info:eu-repo/dai/nl/31400596X; Prokopiou, M.|info:eu-repo/dai/nl/330866117; Sowers, T.; Röckmann, T.|info:eu-repo/dai/nl/304838233; 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

  6. A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Boschker, H.T.S.; Moerdijk-Poortvliet, T.C.W.; Van Breugel, P.; Houtekamer, M.J.; Middelburg, J.J.

    2008-01-01

    We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent

  7. 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

  8. A STUDY OF QUANTUM ISOTOPIC SIEVING THORUGH CARBON NANOTUBES

    OpenAIRE

    Dasgupta, Devagnik

    2013-01-01

    The theory of molecular sieving has long been a subject of importance because of its widespread technological applications .Classical molecular sieving mainly de- pends on the size and shape of the guest molecules and the size of the host solid. However,isotope seperation is usually very difficult to achieve through classical sieving, as the isotopes generally have the same shape and size and differ only in mass.One way to resolve such an issue is through the applications of quantum effects w...

  9. [Carbon Isotope Composition in Landscape Components and Its Changes under Different Ecological Conditions].

    Science.gov (United States)

    Kovda, I V; Morgun, E G; Gongalskii, K B; Balandin, S A; Erokhina, A I

    2016-01-01

    The composition of stable carbon isotopes in plants, plant litter, leaf litter, and soil organic matter was studied experimentally in the western part of the northern foothills of the Caucasus and mountainsides. It was found that the changes in carbon isotope composition depending on the vertical zonation do not exceed 8 per thousand and depend on the type of C3 plant communities, its presence in biogeocenosis components (living matter, plant litter, soil organic matter), and the degree of moistening of the plot studied.

  10. Effect of photosynthetic light dosage on carbon isotope composition in the coral skeleton: Long-term culture of Porites spp.

    Science.gov (United States)

    Omata, Tamano; Suzuki, Atsushi; Sato, Takanori; Minoshima, Kayo; Nomaru, Eriko; Murakami, Akio; Murayama, Shohei; Kawahata, Hodaka; Maruyama, Tadashi

    2008-06-01

    Whereas the oxygen isotope ratio of the coral skeleton is used for reconstruction of past information on seawater, the carbon isotope ratio is considered a proxy for physiological processes, principally photosynthesis and respiration. However, the fractionation of carbon isotopes in biogenic carbonate such as coral skeleton is still unclear. We conducted a long-term culture experiment of Porites spp. corals at different light dosages (light intensity, 100, 300, or 500 μmol m-2 s-1; daily light period, 10 or 12 h) at 25 ± 0.6°C to examine the contribution of photosynthetic activity to skeletal carbon isotope composition. Corals were grown in sand-filtered seawater and not fed; thus, they subsisted from photosynthesis of symbiotic algae. As the daily dose of photosynthetically active radiation increased, the rate of annual extension also increased. Mean isotope compositions shifted; the carbon isotope compositions (δ13C) became heavier and the oxygen isotope compositions (δ18O) became lighter at higher radiation dose. Skeletal δ18O decrease coincided with increasing skeletal growth rate, indicating the influence of so-called kinetic isotope effects. The observed δ13C increase should be subject to both kinetic and metabolic isotope effects, with the latter reflecting skeletal δ13C enrichment due to photosynthesis by symbiotic algae. Using a vector approach in the δ13C-δ18O plane, we discriminated between kinetic and metabolic isotope effects on δ13C. The calculated δ13C changes from metabolic isotope effects were light dose dependent. The δ13C fractionation curve related to metabolic isotope effects is very similar to the photosynthesis-irradiance curve, indicating the direct contribution of photosynthetic activity to metabolic isotope effects. In contrast, δ13C fractionation related to kinetic isotope effects gradually increased as the growth rate increased. Our experiment demonstrated that the kinetic and metabolic isotope effects in coral skeleton

  11. Carbon Stable Isotope Values in Plankton and Mussels Reflect Changes in Carbonate Chemistry Associated with Nutrient Enhanced Net Production

    Science.gov (United States)

    Coastal ecosystems are inherently complex and potentially adaptive as they respond to changes in nutrient loads and climate. We documented the role that carbon stable isotope (δ13C) measurements could play in understanding that adaptation with a series of three Ecostat (i.e...

  12. 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

  13. 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,

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

    Science.gov (United States)

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

    2015-10-01

    ;Clumped-isotope; thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope ;clumps;). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3- and CO32-. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two

  15. 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

    In this study we present the Cr-isotope composition of surface seawater from several locations worldwide. In addition to the samples from the oceans (Atlantic Ocean, Pacific Ocean, Southern Ocean and Artic Ocean) we analysed water samples from areas with a more limited water exchange (Mediterrane...

  16. 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.

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

    Science.gov (United States)

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

    2014-10-01

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

  18. Variability in the carbon isotope fractionation of trichloroethene on its reductive dechlorination by vitamin B12.

    Science.gov (United States)

    Gan, Yiqun; Yu, Tingting; Zhou, Aiguo; Liu, Yunde; Yu, Kai; Han, Li

    2014-08-01

    Stable carbon isotope fractionation through the reductive dechlorination of trichloroethylene by vitamin B12 was determined to assess the possibility of using stable carbon isotope analysis to determine the efficacy of remediation of trichloroethylene using vitamin B12. We elucidated the effects of environmental conditions, including the pH, reaction temperature, and vitamin B12 concentration, on the carbon isotope enrichment factor (ε). The ε values were relatively insensitive to the reaction temperature and vitamin B12 concentration, ranging from -15.7‰ to -16.2‰, with a mean of -15.9 ± 0.2‰, at different temperatures and vitamin B12 concentrations. Such a reproducible ε value could be particularly useful for estimating the extent of degradation in reactions in which a mass balance is difficult to achieve. However, changing the initial solution pH from 6.5 to 9.0 caused a notable change in the ε values, from -14.0‰ to -18.0‰. Reactions were investigated by calculating the apparent kinetic isotope effects for carbon, which, at 1.029-1.037, were smaller than the kinetic isotope effect values previously found for C-Cl bond cleavage. This indicates that a reaction other than the elimination of chloride may be a competitive degradation pathway. The dominant degradation pathway may be different for different initial solution pH values, and this will clearly influence carbon isotope fractionation. Therefore, if the ε value varies with reaction conditions, such as the solution pH, the calculations should take into account the actual environmental conditions that affect the rate limiting pathways.

  19. Triple Oxygen and Clumped Isotopes in Synthetic and Natural Carbonates: Implications for Paleoclimate and Paleohydrology Studies

    Science.gov (United States)

    Laskar, A. H.; Rangarajan, R.; Liang, M. C.

    2016-12-01

    Conventional oxygen isotope (δ18O) has widely been used for paleoclimate studies. However, multiple influencing factors such as temperature, precipitation and kinetic effects during carbonate precipitation complicate the interpretation of δ18O data sometimes. Triple oxygen isotope (Δ17O) in carbonates could be sensitive to kinetic effect occur during its precipitation in water. Carbonates may also record the Δ17O signature of the parent waters, providing a basis in the natural carbonates for identifying kinetic processes such as rapid degassing at lower relative humidity inside a cave during speleothem deposition. Clumped isotopes (Δ47) in carbonates give the formation temperatures of the carbonates if precipitated under isotopic equilibrium. The first goal of the study is to explore the applicability of Δ17O for paleohydrolocial studies. The second is to reconstruct paleotemperature with suitable natural carbonates using Δ47values. This is a rare paleoclimate study utilizing two sophisticated new tools. CO2 produced from carbonates by acid digestion was used for both Δ47 and Δ17O analysis. Purified CO2 samples were directly introduced into the Mass spectrometer (MAT 253) for clumped isotope analysis [1] and CO2-O2 exchange method in presence of platinum for Δ17O analysis [2,3]. We measured Δ47 and Δ17O values in synthetic carbonates precipitated at different temperatures (10-90 oC) and Δ17O values in the water from which the carbonate precipitated. We observed consistent Δ47 values in the carbonates while Δ17O were found to vary. Probably a proper slope (between δ18O and δ17O) selection for carbonates would give consistent results. We also measured Δ47 and Δ17O in modern and well dated speleothems from Chinese and Indian caves to study the paleohydrology and paleotemperature. Δ47 and Δ17O were also measured in modern natural carbonate depositions such as corals, foraminifer and marbles to explore their potentials for paleoclimate studies

  20. Carbon Kinetic Isotope Effects in the Reactions of Atmospheric NMHC with OH, Cl and O3

    Science.gov (United States)

    Anderson, R. S.; Iannone, R.; Thompson, A. E.; Huang, L.; Ernst, D.; Rudolph, J.

    2003-12-01

    It has recently been shown that stable carbon isotope measurements are extremely useful for better understanding of processes involving NMHC in the atmosphere. Knowledge of the isotopic fractionation associated with the chemical removal of NMHC is vital for the interpretation of these measurements. Oxidation by OH-radicals is by far the most important atmospheric removal process of NMHC. Contributions to isotopic fractionation due to removal by reactions with Cl and O3 should also be understood to better interpret stable carbon isotope measurements. From our measurements, in normal urban and background air, reactions with O3 account for 15-25% of the isotopic fractionation in light C2-C4 alkenes. In polar sunrise conditions, reactions with Cl atoms may have a significant impact on the isotopic fractionation in light alkanes. An overview of the measured KIEs for the reactions of C2-C9 NMHC with atmospheric oxidants OH, Cl and O3 will be presented. Possibilities for using specific structural and thermal dependencies of measured KIEs for estimations of unmeasured KIEs of atmospheric interest will be discussed.

  1. Technique for high-precision analysis of triple oxygen isotope ratios in carbon dioxide.

    Science.gov (United States)

    Hofmann, Magdalena E G; Pack, Andreas

    2010-06-01

    Since the discovery of mass-independent isotope effects in stratospheric and tropospheric gases, the analysis of triple oxygen isotope abundance in carbon dioxide gained in importance. However, precise triple oxygen isotope determination in carbon dioxide is a challenging task due to mass-interference of (17)O and (13)C variations. Here, we present a novel analytical technique that allows us to determine slight deviations of CO(2) from the terrestrial fractionation line [TFL]. Our approach is based on isotopic equilibration between CO(2) gas and CeO(2) powder at 685 degrees C and subsequent mass spectrometric analysis of ceria powder by infrared-laser fluorination. We found that beta(CO2-CeO2), the exponent in the relation alpha(17/16) = (alpha(18/16))(beta), amounts to 0.5240 +/- 0.0011 at 685 degrees C. The oxygen isotope anomaly of CO(2) (Delta(17)O) can be determined for a single analysis of CeO(2) with a precision of +/-0.05 per thousand (1sigma). Our CO(2)-CeO(2) equilibration procedure is performed with an excess of CO(2) so that one analysis of Delta(17)O on CO(2) requires at least 3.5 mmol of CO(2) gas. Our new technique allows accurate and precise determination of Delta(17)O in CO(2) and opens up a new field for investigating triple oxygen isotope abundance in various types of natural CO(2).

  2. Calculation of site-specific carbon-isotope fractionation in pedogenic oxide minerals

    Science.gov (United States)

    Rustad, James R.; Zarzycki, Piotr

    2008-01-01

    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 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. PMID:18641124

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

    Science.gov (United States)

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

    2008-12-01

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

  4. 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

  5. Effects of Brine Salinity on Clumped Isotopes and Implications for Applications to Carbonate Diagenesis

    Science.gov (United States)

    Kluge, T.; John, C. M.; Jourdan, A.

    2012-12-01

    Carbonate clumped isotope thermometry relies on the overabundance of 13C-18O bonds in the crystal lattice compared to a stochastic distribution and was calibrated in laboratory experiments using carbonates precipitated from (mainly) de-ionized water that was supersaturated with calcium carbonate (Ghosh et al., 2006). However, the clumped isotope method has also been applied to carbonates that precipitated in the marine and subsurface environments from fluids with significant salt concentrations. These saline fluids differ markedly from the solution used for laboratory calibration. Variations in the electro-chemical potential due to changes in the ion composition and concentration of the solution could influence the physical properties of the clumped isotope bonding and lead to deviations from the commonly used temperature calibration. Consequently, calibrations at high salinities and high temperatures are needed to confidently extend the application of clumped isotopes to diagenetic processes. We investigated the effect of salinity on clumping by precipitating carbonates (mainly calcite) in the laboratory between 23 and 90 °C using a setup analogous to the experiments of Ghosh et al. (2006). A first subset of experiments was performed at low salinities, while during a second subset of experiments we saturated the solution with NaCl (about 35 g/100 ml) in order to mimic a highly saline brine. Since the same experimental procedures were used for both sub-sets (same temperatures of precipitation and rates of nitrogen gas bubbling), we can directly compare clumped isotope values in highly saline versus low-salinity solutions. The initial clumped isotope results obtained from the brine solution agree within uncertainty with results from carbonates precipitated from a NaCl-free solution at the same temperatures. This suggests that clumped isotopes can be applied to carbonates precipitated under highly saline conditions. We acknowledge the financial support of QCCSRC

  6. 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.

  7. Nitrogen and carbon isotope compositions relate linearly in cormorant tissues and its diet

    Energy Technology Data Exchange (ETDEWEB)

    Mizutani, H.; Kabaya, Y.; Wada, E. (Mitsubishi Kasei Inst. of Life Sciences, Tokyo (Japan). Lab. of Biogeochemistry and Sociogeochemistry)

    1991-01-01

    An application of stable isotope distribution of bioelements to ecogeochemical and archaeological studies requires precise knowledge on the relationship between available field samples and diet. As the nature of birds makes it possible to set up an isotopically well defined experiment, nitrogen and carbon isotope relationships between various tissues of a cormorant and its constant diet was studied. The tissues were collected after more than 23 years on the same diet. The two stable isotope ratios for the diet and the tissues showed a high correlation (r=0.92). The linear regression analysis gave the slope of 1.1. Among the tissues examined, skin showed the highest enrichment in both {sup 15}N (4.8per mille) and {sup 13}C (4.2per mille), while brain gave the lowest enrichments (0.8per mille for {sup 15}N and 1.1per mille for {sup 13}C). (orig.).

  8. 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

    “Clumped-isotope” thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope “clumps”). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals.We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect.Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3− and CO32−. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many

  9. Isotopic Constraints on the Genesis of Carbonates in Martian Meteorite ALH 84001

    Science.gov (United States)

    Leshin, Laurie A.

    1999-01-01

    Oxygen isotopic analyses in approximately 20 micrometer spots in a chemically diverse suite of carbonates from ALH 84001 show highly variable delta(exp 18)O values from +5.4 to +25.3%. The isotopic data are correlated with the major element composition of the carbonate. The earliest forming (Ca-rich) carbonates have the lowest delta(exp 18)O values and the late-forming Mg-rich carbonates have the highest delta(exp 18)O values. Two models that can explain the isotopic variation were investigated. The carbonates could have formed in a water-rich environment at relatively low, but highly variable temperatures. In this open-system case the lower limit to the temperature variation is approximately 125 C, with fluctuations of over 250 C possible within the constraints of the model, depending on fluid composition. Alternatively the data can be explained by a closed-system model in which carbonates precipitated from a limited amount of a CO2-rich fluid. This scenario can reproduce the range of isotopic values observed, even at relatively high temperatures (greater than 500 C). Thus, the oxygen isotopic compositions do not provide unequivocal evidence for formation of the carbonates at low temperature. Neither of these scenarios is consistent with a biological origin of the carbonates and their associated features. Olivine from ALH 84001 occurs as clusters within orthopyroxene adjacent to fractures containing disrupted carbonate globules and feldspathic shock glass. The inclusions are irregular in shape and range in size from approximately 40 micrometers to submicrometer. The olivine exhibits a limited range of chemical composition from Fo(sub 65) to Fo(sub 66). We measured delta(exp 18)O values of the olivine to be +5.1 +/- 1.4%, indistinguishable within uncertainty from the host orthopyroxene. The data suggest that the olivine formed at high temperature (greater than 800 C), and is probably unrelated to carbonate formation. Instead the olivine probably formed by

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

    Science.gov (United States)

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

    1993-01-01

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

  11. Suitability of selected free-gas and dissolved-gas sampling containers for carbon isotopic analysis.

    Science.gov (United States)

    Eby, P; Gibson, J J; Yi, Y

    2015-07-15

    Storage trials were conducted for 2 to 3 months using a hydrocarbon and carbon dioxide gas mixture with known carbon isotopic composition to simulate typical hold times for gas samples prior to isotopic analysis. A range of containers (both pierced and unpierced) was periodically sampled to test for δ(13)C isotopic fractionation. Seventeen containers were tested for free-gas storage (20°C, 1 atm pressure) and 7 containers were tested for dissolved-gas storage, the latter prepared by bubbling free gas through tap water until saturated (20°C, 1 atm) and then preserved to avoid biological activity by acidifying to pH 2 with phosphoric acid and stored in the dark at 5°C. Samples were extracted using valves or by piercing septa, and then introduced into an isotope ratio mass spectrometer for compound-specific δ(13)C measurements. For free gas, stainless steel canisters and crimp-top glass serum bottles with butyl septa were most effective at preventing isotopic fractionation (pierced and unpierced), whereas silicone and PTFE-butyl septa allowed significant isotopic fractionation. FlexFoil and Tedlar bags were found to be effective only for storage of up to 1 month. For dissolved gas, crimp-top glass serum bottles with butyl septa were again effective, whereas silicone and PTFE-butyl were not. FlexFoil bags were reliable for up to 2 months. Our results suggest a range of preferred containers as well as several that did not perform very well for isotopic analysis. Overall, the results help establish better QA/QC procedures to avoid isotopic fractionation when storing environmental gas samples. Recommended containers for air transportation include steel canisters and glass serum bottles with butyl septa (pierced and unpierced). Copyright © 2015 John Wiley & Sons, Ltd.

  12. 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.

  13. 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

  14. High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose.

    Science.gov (United States)

    Woodley, Ewan J; Loader, Neil J; McCarroll, Danny; Young, Giles H F; Robertson, Iain; Heaton, Timothy H E; Gagen, Mary H; Warham, Joseph O

    2012-01-30

    Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring α-cellulose samples are used to compare the stable carbon isotope ratios (δ(13)C) produced by high-temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately. Copyright © 2011 John Wiley & Sons, Ltd.

  15. Pre-Existing Carbon Structure and Its Effect on Site-Specific Carbon Isotopes in Small Organic Molecules

    Science.gov (United States)

    Piasecki, A.; Eiler, J. M.

    2014-12-01

    The ability to measure site-specific isotopes in organic molecules allows for better understanding of the mechanisms of their biosynthetic and/or catagenic formation and destruction. Here we examine for site-specific isotopic composition of propane from natural and synthetic sources using novel instruments and techniques gas source mass spectrometry 1, and discuss the possible relationship of our findings to recent independent evidence from NMR measurements for the isotopic structures of long-chain alkanes2. A recent NMR study2 demonstrates that n-alkanes can be divided into three groups according to their site-specific carbon isotope structure: long (C16+) even carbon number, long (C17+) odd carbon number , and short (C11-C15). We modeled the isotopic site-specific composition of propane derived from these three distinct groups. If propane is cleaved from such long-chain hydrocarbons without fractionation, the long odd-numbered and the shorter alkanes would produce propane with an average terminal position 6-7‰ lighter than the center position, while the long even-numbered chain compounds would produce propane with a terminal position averaging around 7‰ heavier than the center. If, instead the fractionation associated with cleaving propane from such parent molecules is ~10‰ (as seems likely), then these average terminal — center differences should be decreased by ~5 ‰ (i.e., to -11-12 and +1-2 ‰, respectively). We will compare these predictions with our previous demonstrations of the changes in bulk and site specific compositions in propane due to isotope exchange equilibria, diffusion and conventional models of kerogen 'cracking', and will use these models as a framework for interpreting the observed site-specific isotopic compositions of propane from diverse natural gas deposits. 1. Piasecki, A. et al. Site-Specific Carbon Isotope Measurement of Organics by Gas Source Mass Spectrometry. Mineralogical Magazine 77, (2013). 2. Gilbert, A., Yamada, K

  16. Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H2 and CO2

    Science.gov (United States)

    Dreisbach, Lisa K.; Conrad, Ralf

    2013-01-01

    Acetogenic bacteria are able to grow autotrophically on hydrogen and carbon dioxide by using the acetyl coenzyme A (acetyl-CoA) pathway. Acetate is the end product of this reaction. In contrast to the fermentative route of acetate production, which shows almost no fractionation of carbon isotopes, the acetyl-CoA pathway has been reported to exhibit a preference for light carbon. In Acetobacterium woodii the isotope fractionation factor (ε) for 13C and 12C has previously been reported to be ε = −58.6‰. To investigate whether such a strong fractionation is a general feature of acetogenic bacteria, we measured the stable carbon isotope fractionation factor of 10 acetogenic strains grown on H2 and CO2. The average fractionation factor was εTIC = −57.2‰ for utilization of total inorganic carbon and εacetate = −54.6‰ for the production of acetate. The strongest fractionation was found for Sporomusa sphaeroides (εTIC = −68.3‰), the lowest fractionation for Morella thermoacetica (εTIC = −38.2‰). To investigate the reproducibility of our measurements, we determined the fractionation factor of 21 biological replicates of Thermoanaerobacter kivui. In general, our study confirmed the strong fractionation of stable carbon during chemolithotrophic acetate formation in acetogenic bacteria. However, the specific characteristics of the bacterial strain, as well as the cultural conditions, may have a moderate influence on the overall fractionation. PMID:23275504

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

    Directory of Open Access Journals (Sweden)

    E. Novelli

    2011-04-01

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

  18. Reconstruction of prehistoric pottery use from fatty acid carbon isotope signatures using Bayesian\

    Czech Academy of Sciences Publication Activity Database

    Fernandes, R.; Eley, Y.; Brabec, Marek; Lucquin, A.; Millard, A.; Craig, O.E.

    2018-01-01

    Roč. 117, March (2018), s. 31-42 ISSN 0146-6380 Institutional support: RVO:67985807 Keywords : Fatty acids * carbon isotopes * pottery use * Bayesian mixing models * FRUITS Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 3.081, year: 2016

  19. An experimental set-up for carbon isotopic analysis of atmospheric ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 122; Issue 3. An experimental set-up for carbon isotopic analysis of atmospheric CO2 and an example of ecosystem response during solar eclipse 2010. Tania Guha Prosenjit Ghosh. Volume 122 Issue 3 June 2013 pp 623-638 ...

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    Japanese cedar leaves from Iwaki, Fukushima were analyzed for carbon, cesium and iodine isotopic compositions before and after the 2011 nuclear accident. The Δ14C values reflect ambient atmospheric 14C concentrations during the year the leaves were sampled/defoliated, and also previous year...

  1. Stable Isotope Values of Nitrogen and Carbon in Particulate Matter: Data

    Science.gov (United States)

    Data set from “Patterns in stable isotope values of nitrogen and carbon in particulate matter from the Northwest Atlantic Continental Shelf, from the Gulf of Maine to Cape Hatteras” by Oczkowski et al. These are the data upon which all results and conclusion are made...

  2. Tracing Raw Materials of Commercially-supplied Mirin by Carbon Stable Isotope Analysis

    National Research Council Canada - National Science Library

    IZU, Hanae; HASHIGUCHI, Tomokazu; HASHIMOTO, Tomoko; MATSUMARU, Katsumi

    2013-01-01

      In this study, we determined the carbon stable isotope ratios of the extract (δ13CEx) and alcohol (δ13CAlc) in commercially-supplied Mirin in order to confirm them as a potential index for verifying the raw-material origins...

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    with magnetostratigraphy in the Santonian-early Campanian interval. The δ13C correlation, supported by calcareous nannofossil biostratigraphy, brings insights into: (1) the position of the Coniacian/Santonian, Santonian/Campanian and Campanian/Maastrichtian boundaries with respect to carbon-isotope stratigraphy...

  4. 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.

  5. Normalization of stable isotope data for carbonate minerals: Implementation of IUPAC guidelines

    Science.gov (United States)

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

    2015-06-01

    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.

  6. Analytical system for stable carbon isotope measurements of low molecular weight (C2-C6) hydrocarbons

    NARCIS (Netherlands)

    Zuiderweg, A.T.; Holzinger, R.; Roeckmann, T.

    2011-01-01

    We present setup, testing and initial results from a new automated system for stable carbon isotope ratio measurements on C2 to C6 atmospheric hydrocarbons. The inlet system allows analysis of trace gases from air samples ranging from a few liters for urban samples and samples with high mixing

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

    Science.gov (United States)

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

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

    DEFF Research Database (Denmark)

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

    2002-01-01

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

  9. Stable carbon isotope fractionation of organic cyst-forming dinoflagellates: Evaluating the potential for a CO

    NARCIS (Netherlands)

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

    2015-01-01

    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,

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

    Science.gov (United States)

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

    2013-09-15

    The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S₂O₈(2-)) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S₂O₈(2-) molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of ∼5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S₂O₈(2-) molar ratio of -7.0 ± 0.2‰ was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S₂O₈(2-) molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. 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 ...

  12. Carbon and Chlorine Isotope Fractionation Patterns Associated with Different Engineered Chloroform Transformation Reactions.

    Science.gov (United States)

    Torrentó, Clara; Palau, Jordi; Rodríguez-Fernández, Diana; Heckel, Benjamin; Meyer, Armin; Domènech, Cristina; Rosell, Mònica; Soler, Albert; Elsner, Martin; Hunkeler, Daniel

    2017-06-06

    To use compound-specific isotope analysis for confidently assessing organic contaminant attenuation in the environment, isotope fractionation patterns associated with different transformation mechanisms must first be explored in laboratory experiments. To deliver this information for the common groundwater contaminant chloroform (CF), this study investigated for the first time both carbon and chlorine isotope fractionation for three different engineered reactions: oxidative C-H bond cleavage using heat-activated persulfate, transformation under alkaline conditions (pH ∼ 12) and reductive C-Cl bond cleavage by cast zerovalent iron, Fe(0). Carbon and chlorine isotope fractionation values were -8 ± 1‰ and -0.44 ± 0.06‰ for oxidation, -57 ± 5‰ and -4.4 ± 0.4‰ for alkaline hydrolysis (pH 11.84 ± 0.03), and -33 ± 11‰ and -3 ± 1‰ for dechlorination, respectively. Carbon and chlorine apparent kinetic isotope effects (AKIEs) were in general agreement with expected mechanisms (C-H bond cleavage in oxidation by persulfate, C-Cl bond cleavage in Fe(0)-mediated reductive dechlorination and E1CB elimination mechanism during alkaline hydrolysis) where a secondary AKIECl (1.00045 ± 0.00004) was observed for oxidation. The different dual carbon-chlorine (Δδ13C vs Δδ37Cl) isotope patterns for oxidation by thermally activated persulfate and alkaline hydrolysis (17 ± 2 and 13.0 ± 0.8, respectively) vs reductive dechlorination by Fe(0) (8 ± 2) establish a base to identify and quantify these CF degradation mechanisms in the field.

  13. elemental and isotopic compositions of organic carbon and nitrogen ...

    African Journals Online (AJOL)

    CARBON AND NITROGEN OF RECENTLY DEPOSITED ORGANIC ... Empakai crater northern Tanzania, is used to document the contents of organic carbon and nitrogen .... erosion. The sedimentation rates in the crater as well as other lakes located in this region are poorly known. Geologically, the study area is studded by.

  14. Carbon and chlorine isotope analysis to identify abiotic degradation pathways of 1,1,1-trichloroethane.

    Science.gov (United States)

    Palau, Jordi; Shouakar-Stash, Orfan; Hunkeler, Daniel

    2014-12-16

    This study investigates dual C-Cl isotope fractionation during 1,1,1-TCA transformation by heat-activated persulfate (PS), hydrolysis/dehydrohalogenation (HY/DH) and Fe(0). Compound-specific chlorine isotope analysis of 1,1,1-TCA was performed for the first time, and transformation-associated isotope fractionation ε bulk C and ε bulk Cl values were -4.0 ± 0.2‰ and no chlorine isotope fractionation with PS, -1.6 ± 0.2‰ and -4.7 ± 0.1‰ for HY/DH, -7.8 ± 0.4‰ and -5.2 ± 0.2‰ with Fe(0). Distinctly different dual isotope slopes (Δδ13C/Δδ37Cl): ∞ with PS, 0.33 ± 0.04 for HY/DH and 1.5 ± 0.1 with Fe(0) highlight the potential of this approach to identify abiotic degradation pathways of 1,1,1-TCA in the field. The trend observed with PS agreed with a C-H bond oxidation mechanism in the first reaction step. For HY/DH and Fe(0) pathways, different slopes were obtained although both pathways involve cleavage of a C-Cl bond in their initial reaction step. In contrast to the expected larger primary carbon isotope effects relative to chlorine for C-Cl bond cleavage, ε bulk C isotope effects. Therefore, different magnitude of secondary chlorine isotope effects could at least be partly responsible for the distinct slopes between HY/DH and Fe(0) pathways. Following this dual isotope approach, abiotic transformation processes can unambiguously be identified and quantified.

  15. Observations and sources of carbon and nitrogen isotope ratio variation of pentaerythritol tetranitrate (PETN).

    Science.gov (United States)

    Howa, John D; Lott, Michael J; Ehleringer, James R

    2014-11-01

    Isotope ratio analysis allows forensic investigators to discriminate materials that are chemically identical but differ in their isotope ratios. Here we focused on the discrimination of pentaerythritol tetranitrate (PETN), an explosive with military and civilian applications, using carbon (δ(13)C) and nitrogen (δ(15)N) isotope ratios. Our goal was to understand some of the factors influencing the isotope ratios of commercially manufactured PETN. PETN was isolated from bulk explosives using preparative HPLC, which reduced chemical and isotopic within-sample variability. We observed isotope ratio variation in a survey of 175 PETN samples from 22 manufacturing facilities, with δ(13)C values ranging from -49.7‰ to -28.0‰ and δ(15)N values ranging from -48.6‰ to +6.2‰. Both within-sample variability and variation of PETN within an explosive block were much smaller than between-sample variations. Isotopic ratios of PETN were shown to discriminate explosive blocks from the same manufacturer, whereas explosive component composition measurements by HPLC were not able to do so. Using samples collected from three industrial PETN manufacturers, we investigated the isotopic relationship between PETN and its reactants, pentaerythritol (PE) and nitric acid. Our observations showed that δ(13)C values of PETN were indistinguishable from that of the reactant pentaerythritol. Isotopic separation between nitric acid and PETN was consistent within each sampled manufacturer but differed among manufacturers, and was likely dependent upon reaction conditions. These data indicate that δ(13)C variation in PETN is dependent on δ(13)C variation of PE supplies, while δ(15)N variation in PETN is due to both nitric acid δ(15)N and reaction conditions. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  16. Evaluating the deep-ocean circulation of a global ocean model using carbon isotopic ratios

    Science.gov (United States)

    Paul, André; Dutkiewicz, Stephanie; Gebbie, Jake; Losch, Martin; Marchal, Olivier

    2016-04-01

    We study the sensitivity of a global three-dimensional biotic ocean carbon-cycle model to the parameterizations of gas exchange and biological productivity as well as to deep-ocean circulation strength, and we employ the carbon isotopic ratios δ13C and Δ14C of dissolved inorganic carbon for a systematic evaluation against observations. Radiocarbon (Δ14C) in particular offers the means to assess the model skill on a time scale of 100 to 1000 years relevant to the deep-ocean circulation. The carbon isotope ratios are included as tracers in the MIT general circulation model (MITgcm). The implementation involves the fractionation processes during photosynthesis and air-sea gas exchange. We present the results of sixteen simulations combining two different parameterizations of the piston velocity, two different parameterizations of biological productivity (including the effect of iron fertilization) and four different overturning rates. These simulations were first spun up to equilibrium (more than 10,000 years of model simulation) and then continued from AD 1765 to AD 2002. For the model evaluation, we followed the OCMIP-2 (Ocean Carbon-Cycle Model Intercomparision Project phase two) protocol, comparing the results to GEOSECS (Geochemical Ocean Sections Survey) and WOCE (World Ocean Circulation Experiment) δ13C and natural Δ14C data in the world ocean. The range of deep natural Δ14C (below 1000 m) for our single model (MITgcm) was smaller than for the group of different OCMIP-2 models. Furthermore, differences between different model parameterizations were smaller than for different overturning rates. We conclude that carbon isotope ratios are a useful tool to evaluate the deep-ocean circulation. Since they are also available from deep-sea sediment records, we postulate that the simulation of carbon isotope ratios in a global ocean model will aid in estimating the deep-ocean circulation and climate during present and past.

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

    Science.gov (United States)

    Kimball, Justine; Eagle, Robert; Dunbar, Robert

    2016-12-01

    Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near-constant temperature, salinity, and pH and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop "clumped" isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate-related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures, and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ47-temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ47-temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset

  18. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  19. Ca Isotopes in Shallow Water Marine Carbonates - How I Learned to Stop Worrying and Embrace Diagenesis

    Science.gov (United States)

    Higgins, J. A.; Blättler, C. L.; Swart, P. K.; Santiago Ramos, D. P.; Akhtar, A.

    2016-12-01

    The geochemistry of shallow water carbonate sediments has been used to reconstruct the temperature and isotopic composition of seawater as well as the global carbon and oxygen cycles over >3 billion years of Earth history. An underlying and heavily debated assumption in most studies utilizing the chemistry of carbonate minerals is that the chemical composition of the sample accurately preserves a record of the fluid from which it precipitated. Diagenetic or post-depositional alteration of the geochemistry by either meteoric or marine fluids is a widespread phenomenon in modern and recent shallow and deep-sea carbonate sediments. Diagenetic alteration is observed at all scales, from micron, to thin section, to stratigraphic units, making it difficult to quantify its effects on the geochemistry of carbonate sediments in the geologic record. Here we explore the possibility of using the Ca isotopic composition of sedimentary carbonates as a diageneitc tool using a large data set of Neogene carbonate sediments and associated pore fluids from the Bahamas. We find that the δ44/40Ca values of bulk carbonate sediments at these sites exhibits systematic stratigraphic variability that is related to both mineralogy and diagenesis (marine and meteoric). The observed variability in bulk sediment Ca isotopes requires large-scale fluid-dominated early marine diagenesis in significant water depths (up to 650 mbsl) and suggests that fluid-dominated early marine diagenesis plays a fundamental role in determining the geochemistry (δ13C, δ18O, and trace elements) of shallow water carbonate sediments in the geologic record.

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

    Directory of Open Access Journals (Sweden)

    Petrella Emma

    2013-01-01

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

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

    OpenAIRE

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2004-01-01

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

  3. Neodymium associated with foraminiferal carbonate as a recorder of seawater isotopic signatures

    Science.gov (United States)

    Tachikawa, Kazuyo; Piotrowski, Alexander M.; Bayon, Germain

    2014-03-01

    Neodymium isotopic ratios in marine environments have been used as a tracer of water masses and exchange processes between dissolved and particulate phases. The interest in this tracer has been growing with improvement of our knowledge on its chemical behaviour in the modern ocean and the identification of sedimentary phases that preserve past seawater ɛNd values. In the last few decades the Nd isotopic composition measured on Fe-Mn crusts, sediment leachates, bulk carbonate fraction, corals and fish teeth have been increasingly interpreted in the context of understanding the role of the ocean in paleoclimate changes. In particular, calcareous foraminiferal tests (shells) have acquired increasing attention as an archive of seawater Nd isotopic signatures, because it allows continuous high-resolution records to be measured and directly compared to other proxies including stable isotopes and trace metals. The main challenge of interpreting the Nd isotopic composition of foraminifera is determining the origin of the Nd preserved within them. In this review, we present an overview of methodological progress including that of bulk foraminifera and microanalyses within foraminiferal tests, as well as geochemical meaning of extracted Nd concentrations and isotopic compositions. The growing body of evidence suggests that Nd isotopic signatures of sedimentary planktonic foraminifera correspond to bottom water values rather than surface water ones. The Nd-rich phases associated with sedimentary foraminifera are adhesive nano-scale particles of Mn and Fe oxides and hydroxides, and Mn-rich carbonates formed within layers of foraminiferal calcite. Mechanical cleaning to remove clay minerals is likely to be sufficient in most cases to reconstruct past bottom water circulations. Unresolved issues include the potential influence of pore water Nd on ɛNd values extracted from sedimentary foraminiferal tests under different sedimentalogical and oceanographic conditions.

  4. Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral.

    Science.gov (United States)

    Yoshimura, Toshihiro; Tanimizu, Masaharu; Inoue, Mayuri; Suzuki, Atsushi; Iwasaki, Nozomu; Kawahata, Hodaka

    2011-11-01

    High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification technique. The mean δ(26)Mg values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were -0.87‰, -2.57‰, -2.34‰, and -2.43‰, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization. Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 °C to 19.5 °C: 1,000 × ln(α) = -2.63 (±0.076) + 0.0138 (±0.0051) × T(R(2) = 0.82, p isotope fractionation may not be a major controlling factor for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element partitioning and the calcification rate of biogenic CaCO(3), the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical control on Mg isotope fractionation for high-Mg calcite. On the other hand, δ(26)Mg in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges, and scaphopad, regardless of species differences of samples.

  5. Enantioselective carbon stable isotope fractionation of hexachlorocyclohexane during aerobic biodegradation by Sphingobium spp.

    Science.gov (United States)

    Bashir, Safdar; Fischer, Anko; Nijenhuis, Ivonne; Richnow, Hans-Hermann

    2013-10-15

    Carbon isotope fractionation was investigated for the biotransformation of γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers of α-HCH using two aerobic bacterial strains: Sphingobium indicum strain B90A and Sphingobium japonicum strain UT26. Carbon isotope enrichment factors (ε(c)) for γ-HCH (ε(c) = -1.5 ± 0.1 ‰ and -1.7 ± 0.2 ‰) and α-HCH (ε(c) = -1.0 ± 0.2 ‰ and -1.6 ± 0.3 ‰) were similar for both aerobic strains, but lower in comparison with previously reported values for anaerobic γ- and α-HCH degradation. Isotope fractionation of α-HCH enantiomers was higher for (+) α-HCH (ε(c) = -2.4 ± 0.8 ‰ and -3.3 ± 0.8 ‰) in comparison to (-) α-HCH (ε(c) = -0.7 ± 0.2 ‰ and -1.0 ± 0.6 ‰). The microbial fractionation between the α-HCH enantiomers was quantified by the Rayleigh equation and enantiomeric fractionation factors (ε(e)) for S. indicum strain B90A and S. japonicum strain UT26 were -42 ± 16% and -22 ± 6%, respectively. The extent and range of isomer and enantiomeric carbon isotope fractionation of HCHs with Sphingobium spp. suggests that aerobic biodegradation of HCHs can be monitored in situ by compound-specific stable isotope analysis (CSIA) and enantiomer-specific isotope analysis (ESIA). In addition, enantiomeric fractionation has the potential as a complementary approach to CSIA and ESIA for assessing the biodegradation of α-HCH at contaminated field sites.

  6. Population and individual foraging patterns of two hammerhead sharks using carbon and nitrogen stable isotopes.

    Science.gov (United States)

    Loor-Andrade, P; Galván-Magaña, F; Elorriaga-Verplancken, F R; Polo-Silva, C; Delgado-Huertas, A

    2015-05-15

    Individual foraging behavior is an important variable of predators commonly studied at the population level. Some hammerhead shark species play a significant role in the marine ecosystem as top consumers. In this context, stable isotope analysis allows us to infer some ecological metrics and patterns that cannot usually be obtained using traditional methods. We determined the isotopic composition (δ(13)C and δ(15)N values) of dorsal muscle and vertebrae of Sphyrna lewini and Sphyrna zygaena using a continuous-flow system consisting of an elemental analyzer combined with a Delta Plus XL mass spectrometer. Foraging variability by sex and by individual was inferred from the isotopic values. There were no significant differences in the isotopic values of muscle samples between sexes, but there were differences between species. The trophic niche breadth of the two species was similar and overlap was low. A low niche overlap was observed between S. lewini individual vertebrae. We found differences in the δ(15)N values of S. zygaena vertebrae, with lower values in the first group of samples. Despite these hammerhead shark species inhabiting the same area, there was low trophic niche overlap between species and individuals, due to different individual foraging strategies, according to the carbon and nitrogen isotopic profiles obtained. The use of tissues that retain lifetime isotopic information is useful to complement studies on trophic ecology. Copyright © 2015 John Wiley & Sons, Ltd.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-03

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

  8. The carbon isotope ecology and diet of Australopithecus africanus at Sterkfontein, South Africa.

    Science.gov (United States)

    van der Merwe, Nikolaas J; Thackeray, J Francis; Lee-Thorp, Julia A; Luyt, Julie

    2003-05-01

    The stable carbon isotope ratio of fossil tooth enamel carbonate is determined by the photosynthetic systems of plants at the base of the animal's foodweb. In subtropical Africa, grasses and many sedges have C(4)photosynthesis and transmit their characteristically enriched 13C/(12)C ratios (more positive delta13C values) along the foodchain to consumers. We report here a carbon isotope study of ten specimens of Australopithecus africanus from Member 4, Sterkfontein (ca. 2.5 to 2.0Ma), compared with other fossil mammals from the same deposit. This is the most extensive isotopic study of an early hominin species that has been achieved so far. The results show that this hominin was intensively engaged with the savanna foodweb and that the dietary variation between individuals was more pronounced than for any other early hominin or non-human primate species on record. Suggestions that more than one species have been incuded in this taxon are not supported by the isotopic evidence. We conclude that Australopithecus africanus was highly opportunistic and adaptable in its feeding habits.

  9. Stable carbon and hydrogen isotope fractionation of dissolved organic groundwater pollutants by equilibrium sorption.

    Science.gov (United States)

    Höhener, Patrick; Yu, Xianjing

    2012-03-15

    Linear free energy relationships (LFERs) were established which relate equilibrium vapor-liquid isotope effects to stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to geosorbents. The LFERs were established for normal, cyclic or branched alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. Defining fractionation as in classical literature by "heavy divided by light", carbon enrichment factors for equilibrium sorption were derived which ranged from -0.13±0.04‰ (benzene) to -0.52±0.19‰ (trichloroethene at 5-15 °C). Hydrogen enrichment factors for sorption of 14 different compounds were between -2.4 and -9.2‰. For perdeuterated hydrocarbons the predicted enrichment factors ranged from -19±5.4‰ (benzene) to -64±30‰ (cyclohexane). Equilibrium sorption experiments with a soil and activated carbon as sorbents were performed in the laboratory for perdeuterocyclohexane and perdeuterotoluene. The measured D/H enrichments agreed with the LFER prediction for both compounds and both sorbents within the uncertainty estimate of the prediction. The results of this work suggest that equilibrium sorption does create only very small isotope shifts for (13)C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. 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.

  11. 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).

  12. 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

  13. Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts.

    Science.gov (United States)

    Sakai, H; Des Marais, D J; Ueda, A; Moore, J G

    1984-01-01

    Fresh submarine basalt glasses from Galapagos Ridge, FAMOUS area, Cayman Trough and Kilauea east rift contain 22 to 160 ppm carbon and 0.3 to 2.8 ppm nitrogen, respectively, as the sums of dissolved species and vesicle-filling gases (CO2 and N2). The large range of variation in carbon content is due to combined effect of depth-dependency of the solubility of carbon in basalt melt and varying extents of vapour loss during magma emplacement as well as in sample crushing. The isotopic ratios of indigenous carbon and nitrogen are in very narrow ranges, -6.2 +/- 0.2% relative to PDB and +0.2 +/- 0.6% relative to atmospheric nitrogen, respectively. In basalt samples from Juan de Fuca Ridge, however, isotopically light carbon (delta 13 C = around -24%) predominates over the indigenous carbon; no indigenous heavy carbon was found. Except for Galapagos Ridge samples, these ocean-floor basalts contain 670 to 1100 ppm sulfur, averaging 810 ppm in the form of both sulfide and sulfate, whereas basalts from Galapagos Ridge are higher in both sulfur (1490 and 1570 ppm) and iron (11.08% total iron as FeO). the delta 34S values average +0.3 +/- 0.5% with average fractionation factor between sulfate and sulfide of +7.4 +/- 1.6%. The sulfate/sulfide ratios tend to increase with increasing water content of basalt, probably because the oxygen fugacity increases with increasing water content in basalt melt.

  14. Cryogenic Carbonate Formation on Mars: Clues from Stable Isotope Variations Seen in Experimental Studies

    Science.gov (United States)

    Socki, Richard A.; Niles, Paul B.; Fu, Qi; Gibson, Everett K., Jr.

    2010-01-01

    Discoveries of large deposits of sedimentary materials on the planet Mars by landers and orbiters have confirmed the widely held hypothesis that water has played a crucial role in the development of the martian surface. Recent studies have indicated that both water ice and liquid water may have been present and in the case of water ice perhaps is still present on or near the surface of Mars. However, there remains much controversy about the prevailing atmospheric conditions and climate of Mars during its history and whether liquid water existed on the martian surface simply during discrete geological events or whether this water was present over relatively much longer geologic time periods. The recent identification of Ca-rich carbonate by the Phoenix lander as well as its measurement of the isotopic composition of atmospheric CO2 has shown the importance of understanding the carbonates on Mars as an important sink of atmospheric carbon. This work compliments that of our past experiments where we produced cryogenic calcite in open containers, as analogs for terrestrial aufeis formation, and as a means for evaluating the fractionation of C-13 in CO2 during bicarbonate freezing [13]. Unlike our previous experiments in which carbonates were grown in ambient laboratory condition in open containers (atmospheric pressure and composition), this work attempts to quantify the amount of delta C-13 enrichment possible in both fluids and secondary carbonates formed from freezing of bicarbonate fluids under martian-like atmospheric conditions. Morphologic textures of produced carbonates in these experiments are also examined under SEM in order to identify the effect that the cryogenic freezing process has on the mineral's mineralogy. Understanding the role of kinetic isotope fractionation during formation of carbonates under martian-like conditions will aid in our ability to quantify the isotopic composition of the carbonate sink furthering our ability to model the climate

  15. Sedimentary evidence for enhanced hydrological cycling in response to rapid carbon release during the early Toarcian oceanic anoxic event

    Science.gov (United States)

    Izumi, Kentaro; Kemp, David B.; Itamiya, Shoma; Inui, Mutsuko

    2018-01-01

    A pronounced excursion in the carbon-isotope composition of biospheric carbon and coeval seawater warming during the early Toarcian (∼183 Ma) has been linked to the large-scale transfer of 12C-enriched carbon to the oceans and atmosphere. A European bias in the distribution of available data means that the precise pattern, tempo and global expression of this carbon cycle perturbation, and the associated environmental responses, remain uncertain. Here, we present a new cm-scale terrestrial-dominated carbon-isotope record through an expanded lower Toarcian section from Japan that displays a negative excursion pattern similar to marine and terrestrial carbon-isotope records documented from Europe. These new data suggest that 12C-enriched carbon was added to the biosphere in at least one rapid, millennial-scale pulse. Sedimentological analysis indicates a close association between the carbon-isotope excursion and high-energy sediment transport and enhanced fluvial discharge. Together, these data support the hypothesis that a sudden strengthening of the global hydrological cycle occurred in direct and immediate response to rapid carbon release and atmospheric warming.

  16. Late Permian-earliest Triassic high-resolution organic carbon isotope and palynofacies records from Kap Stosch (East Greenland)

    Science.gov (United States)

    Sanson-Barrera, Anna; Hochuli, Peter A.; Bucher, Hugo; Schneebeli-Hermann, Elke; Weissert, Helmut; Adatte, Thierry; Bernasconi, Stefano M.

    2015-10-01

    During and after the end Permian mass extinction terrestrial and marine biota underwent major changes and reorganizations. The latest Permian and earliest Triassic is also characterized by major negative carbon isotope shifts reflecting fundamental changes in the carbon cycle. The present study documents a high-resolution bulk organic carbon isotope record and palynofacies analysis spanning the latest Permian-earliest Triassic of East Greenland. An almost 700 meter thick composite section from Kap Stosch allowed discriminating 6 chemostratigraphic intervals that provide the basis for the correlation with other coeval records across the world, and for the recognition of basin wide transgressive-regressive events documenting tectonic activity during the opening of the Greenland-Norway Basin. The identification of the main factors that influenced the organic carbon isotope signal during the earliest Triassic (Griesbachian to Dienerian) was possible due to the combination of bulk organic carbon isotope, palynofacies and Rock-Eval data. Two negative carbon isotopic shifts in the Kap Stosch record can be correlated with negative shifts recorded in coeval sections across the globe. A first negative shift precedes the base of the Triassic as defined by the first occurrence of the conodont Hindeodus parvus in the Meishan reference section, and the second one coincides with the suggested Griesbachian-Dienerian boundary. This new organic carbon isotope record from the extended Kap Stosch section from the Boreal Realm documents regional and global carbon cycle signals of the interval between the latest Palaeozoic and the onset of the Mesozoic.

  17. Noble gas and carbon isotopes in Mariana Trough basalt glasses

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, M. [Centre de Recherches Petrographiques et Geochimiques, Centre National de la Recherche Scientifique, Rue Notre-Dame des Pauvres, BP 20, 54501 Vandoeuvre Cedex (France); Jambon, A. [Laboratoire de Magmatologie et Geochimie Inorganique et Experimentale, Universite Pierre et Marie Curie, F-75252 Paris Cedex 05 (France); Gamo, T. [Ocean Research Institute, The University of Tokyo, Nakano-ku Tokyo 164 (Japan); Nishio, Y. [Geological Institute, The University of Tokyo, Bunkyo-ku Tokyo 113 (Japan); Sano, Y. [Department of Earth and Planetary Sciences, Hiroshima University, Kagamiyama Higashi Hiroshima 739 (Japan)

    1998-06-01

    oble gas elemental and isotopic compositions have been measured as well as the abundance of C and its isotopic ratios in 11 glasses from submarine pillow basalts collected from the Mariana Trough. The {sup 3}He/{sup 4}He ratios of 8.22 and 8.51 R{sub atm} of samples dredged from the central Mariana Trough (similar18N) agree well with that of the Mid-Ocean Ridge Basalt (MORB) glasses (8.4{+-}0.3 R{sub atm}), whereas a mean ratio of 8.06{+-}0.35 R{sub atm} in samples from the northern Mariana Trough (similar20N) is slightly lower than those of MORB. One sample shows apparent excess of {sup 20}Ne and {sup 21}Ne relative to atmospheric Ne, suggesting incorporation of solar-type Ne in the magma source. There is a positive correlation between {sup 3}He/{sup 4}He and {sup 40}Ar/{sup 36}Ar ratios, which may be explained by mixing between MORB-type and atmospheric noble gases. Excess {sup 129}Xe is observed in the sample which also shows {sup 20}Ne and {sup 21}Ne excesses. Observed {delta}{sup 13}C values of similar20N samples vary from -3.76 per thousand to -2.80 per thousand, and appear higher than those of MORB, and the corresponding CO{sub 2}/{sup 3}He ratios are higher than those of MARA samples at similar18N, suggesting C contribution from the subducted slab. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  18. The carbon-isotopic composition of Proterozoic carbonates: Riphean successions from northwestern Siberia (Anabar Massif, Turukhansk Uplift)

    Science.gov (United States)

    Knoll, A. H.; Kaufman, A. J.; Semikhatov, M. A.

    1995-01-01

    Thick carbonate-dominated successions in northwestern Siberia document secular variations in the C-isotopic composition of seawater through Mesoproterozoic and early Neoproterozoic (Early to early Late Riphean) time. Mesoproterozoic dolomites of the Billyakh Group, Anabar Massif, have delta 13C values that fall between 0 and -1.9 permil versus PDB, with values in the upper part of the succession (Yusmastakh Formation) consistently higher than those of the lower (Ust'-Il'ya and Kotuikan formations). Consistent with available biostratigraphic and radiometric data, delta 13C values for Billyakh carbonates compare closely with those characterizing early Mesoproterozoic carbonates (about 1600-1200 Ma) worldwide. In contrast, late Mesoproterozoic to early Neoproterozoic limestones and dolomites in the Turukhansk Uplift exhibit moderate levels of secular variation. Only the lowermost carbonates in the Turukhansk succession (Linok Formation) have delta 13C values that approximate Billyakh values. Higher in the Turukhansk succession, delta 13C values vary from -2.7 to +4.6 permil (with outliers as low as -5.0 permil interpreted as diagentically altered). Again, consistent with paleontological and radiometric data, these values compare well with isotopic values from 1200 to 850 Ma successions elsewhere. Five sections measured in different parts of the Turukhansk basin show nearly identical patterns of variation, confirming that carbonate delta 13C correlates primarily with time and not facies. The Siberian sections illustrate the potential of integrated biostratigraphic and chemostratigraphic data in the intra- and interbasinal correlation of Mesoproterozoic and early Neoproterozoic rocks.

  19. Stable isotope analysis of carbonates from the W-Hungarian natural CO2 occurrence

    Science.gov (United States)

    Cseresznyés, Dóra; Czuppon, György; Szabó, Zsuzsanna; Király, Csilla; Szabó, Csaba; Falus, György

    2017-04-01

    Carbone capture and storage is becoming more vital in the last years because the concentration of carbon-dioxide is constantly increasing in the atmosphere in relation with anthropogenic emissions. To reach the long-term safety of CO2 geological storage, it is needed to be aware of the geological environment, its behavior, and the influence of the complex physical and chemical reactions on the investigated system. The study of natural CO2 occurrences can help us to understand and predict what processes are likely to occur in CO2 geological storage reservoirs in geological time scales. In the presented work we provide a detailed insight into the stable isotope composition of different carbonate minerals of a natural CO2 reservoir from the Mihályi Répcelak area, W-Hungary. The study of stable isotope systems provides important information on the time of CO2 flooding and the origin of CO2. We measured the C and O isotope composition of different carbonate minerals, ankerite, dawsonite and siderite, as well as the H isotopes in dawsonite. The measurements both on separated mineral grains and whole rock sample were carried out. The analyses of C and O stable isotopes in separated carbonates was performed with Thermo Finnigan Delta Plus XP mass spectrometer. H stable isotope measurement was conducted on whole rocks applying LWIA-24d type laser analyser. Using the obtained isotopic values the δ13C values of CO2 in equilibrium with dawsonite and the δ18O values of water in equilibrium with carbonate minerals were calculated. The results of C and O isotopes are the following: δ 13CPDB values on average are ankerite: 1.86 ‰, dawsonite: 1.53 ‰ to 1.56 ‰, siderite: 2.07 ‰ and δ 18OSMOW values ankerite: 22.15 ‰, dawsonite: 19.46 ‰ to 19.54 ‰, siderite: 22.99 ‰. Values of δDSMOW for dawsonite vary between -73.14 ‰ and -74.31 ‰. The calculated value of δ13C of CO2 in equilibrium with dawsonite ranges between -4.55 and 2.58 ‰. These values indicate

  20. RECONSTRUCTION OF PAST CLIMATE BASING ON THE ISOTOPIC COMPOSITION OF CARBON FROM FOSSIL REMAINS

    Directory of Open Access Journals (Sweden)

    Vladimir Nikolaev

    2012-01-01

    Full Text Available The areas of Northern Eurasia and the Far North regions with a sharply continental climate are of particular interest to paleoclimatologists. The nature of these areas preserves many features of the Late Glacial period. However, the reliability of the classical paleoclimatic methods in these areas is low. It is known that climate may affect the δ13C value of plants, causing isotopic variations of up to 3‰. The authors propose to use the carbon isotope compositions of bone carbonate of herbivorous animals as a paleoclimatic indicator for the Polar Regions.To test the potential of the proposed paleoclimatic indicator, the authors studied the carbon isotopic composition of carbonate of bone (reliably dated by the radiocarbon method of Late Pleistocene mammals (mammoth mostly from the area of the Lena River delta—the New Siberian Islands—Oyagossky Yar (the total of 43 samples. These data suggest that the Late Pleistocene climate in North Yakutia was not stable. Instability was expressed in the sharp, short-term (500–2000 years, occasional episodes of relatively warm climate that may be ranked as interstadials based on their intensity.

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

    DEFF Research Database (Denmark)

    Kristensen, Ditte Katrine; 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...... 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...... plant groups was compared with those of muskox faeces and shed wool, as this is a noninvasive approach to obtain dietary information on different temporal scales. Plants with different root mycorrhizal status were found to have different d15N values, whereas differences in d13C, as expected, were less...

  2. Utility of 5A molecular sieves to measure carbon isotope ratios in lipid biomarkers.

    Science.gov (United States)

    Tolosa, Imma; Ogrinc, Nives

    2007-09-21

    A procedure using 5A zeolite sorption to separate cyclic/branched organic compounds from the linear ones was developed and carbon isotopic fractionation effects were investigated in different families of compounds, e.g. within the hydrocarbon and alcohol compounds. The 5A sieve has a pore size such that only linear components can be incorporated into the pores whereas the cyclic/branched compounds are remaining free in the organic solution. The sorbed compounds were released from the molecular sieve with HF and solvent extracted with hexane. The method enables the isolation of linear saturated classes, such as n-alkanes and n-fatty alcohols from branched/cyclic compounds without isotopic fractionation for compound-specific isotope analysis (CSIA) of delta(13)C. However, alkene hydrocarbons, sterols and some aromatics were completely or partly degraded with the molecular sieve.

  3. Stable isotope composition of bulk and secondary carbonates from the Quaternary loess-paleosol sequence in Sutto, Hungary

    DEFF Research Database (Denmark)

    Koeniger, Paul; Barta, Gabriella; Thiel, Christine

    2014-01-01

    Stable carbon and oxygen isotope composition of pedogenic carbonates were studied from the Quaternary loess-paleosol sequence of Sutto in Hungary to investigate genetic processes in a paleoenvironmental context and to distinguish subtypes. Bulk carbonate samples taken at 2 cm vertical resolution...

  4. Carbon and hydrogen isotopic compositions of algae and bacteria from hydrothermal environments, Yellowstone National Park

    Energy Technology Data Exchange (ETDEWEB)

    Estep, M.L.E.

    1984-03-01

    Stromatolites forming today on a small scale in hydrothermal environments are chemical and biological analogues of much larger Precambrian formations. Carbon isotopic composition varied as a function of CO/sub 2/ concentration, pH, and species composition. Stratiform, layered stromatolites grew in silica-depositing springs at 55/sup 0/ to 70/sup 0/C; they consisted mainly of a unicellular alga, Synechococcus, and a filamentous, photosynthetic bacterium, Chloroflexus. These thermophiles become enriched in /sup 12/C as the concentration of carbon dioxide in the effluent waters increases. At a concentration of 40 ppm total inorganic C, and delta/sup 13/C of organic carbon was approx. -1.2%, whereas at 900 ppm total inorganic C, the delta/sup 13/C of similar species was approx. -2.5%. Conical stromatolites or conophytons (principally a filamentous, blue-green alga Phormidium and Chloroflexus) grew at 40/sup 0/-55/sup 0/C. In older, broader conophytons, Chloroflexus was the dominant organism. Their delta/sup 13/C values were approx. -1.8% in a variety of hot springs. In carbonate-depositing springs, i.e., carbon dioxide saturated, conophytons and stromatolites consisting of a variety of blue-green algae and photosynthetic bacteria had the most negative delta/sup 13/C values (to -3 %). These carbon isotope ratios are directly comparable to carbon isotope ratios of kerogen from Precambrian stromatolites. The presence and activity of methanogenic bacteria or heterotrophic, aerobic and anaerobic bacteria did not alter significantly the delta/sup 13/C of the original organic matter.

  5. High-resolution carbon cycle and seawater temperature evolution during the Early Jurassic (Sinemurian-Early Pliensbachian)

    Science.gov (United States)

    Price, Gregory D.; Baker, Sarah J.; VanDeVelde, Justin; Clémence, Marie-Emilie

    2016-10-01

    The Early Jurassic was marked by a progressive recovery from the end-Triassic mass extinction and punctuated by recurring episodes of anoxia. These changes, associated with fluctuations in carbon isotope composition of marine carbonates, remain incompletely understood. Here we present a high-resolution carbon and oxygen isotope record for the Early Jurassic based on well-preserved marine mollusks (belemnites) from Dorset, UK. Our new data show a number of δ13C excursions, starting with a negative excursion at the Sinemurian-Pliensbachian boundary Event followed by lesser negative excursions showing in the Polymorphous, Jamesoni, and Masseanum-Valdani Subzones. The recognition of the Sinemurian-Pliensbachian boundary Event in this study and elsewhere suggests that observed carbon-isotope trends are likely to represent a supraregional perturbation of the carbon cycle. A prominent positive carbon-isotope event is also seen within the Pliensbachian Ibex Zone. This event is also clearly evident in the data from belemnites from Spain. This carbon-isotope excursion is not, however, coincident with inferred peak temperatures. The oxygen isotope and Mg/Ca data allow the determination of a number of pronounced Pliensbachian cool events. From the low point in the Brevispina Subzone, oxygen isotopes become more negative coupled with an increase in Mg/Ca values culminating in an Early Pliensbachian thermal maximum during the Davoei Zone. Taken with existing data, it appears that the Pliensbachian is characterized by two major warmings, first within the Davoei Zone followed by warming beginning in the latest Pliensbachian and peaking in the Early Toarcian.

  6. 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.

  7. Framing Learning Conditions in Geography Excursions

    Science.gov (United States)

    Jonasson, Mikael

    2011-01-01

    The aim of this paper is to investigate and frame some learning conditions involved in the practice of geographical excursions. The empirical material from this study comes from several excursions made by students in human geography and an ethnomethodological approach through participant observation is used. The study is informed by theories from…

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

    Science.gov (United States)

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

    2015-12-01

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

  9. Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen.

    Science.gov (United States)

    Nachev, Milen; Jochmann, Maik A; Walter, Friederike; Wolbert, J Benjamin; Schulte, S Marcel; Schmidt, Torsten C; Sures, Bernd

    2017-02-17

    Stable isotope analysis of carbon and nitrogen can deliver insights into trophic interactions between organisms. While many studies on free-living organisms are available, the number of those focusing on trophic interactions between hosts and their associated parasites still remains scarce. In some cases information about taxa (e.g. acanthocephalans) is completely missing. Additionally, available data revealed different and occasionally contrasting patterns, depending on the parasite's taxonomic position and its degree of development, which is most probably determined by its feeding strategy (absorption of nutrients through the tegument versus active feeding) and its localization in the host. Using stable isotope analysis of carbon and nitrogen we provided first data on the trophic position of an acanthocephalan species with respect to its fish host. Barbels (Barbus barbus) infected only with adult acanthocephalans Pomphorhynchus laevis as well as fish co-infected with the larval (L4) nematodes Eustrongylides sp. from host body cavity were investigated in order to determine the factors shaping host-parasite trophic interactions. Fish were collected in different seasons, to study also potential isotopic shifts over time, whereas barbels with single infection were obtained in summer and co-infected ones in autumn. Acanthocephalans as absorptive feeders showed lower isotope discrimination values of δ (15)N than the fish host. Results obtained for the acanthocephalans were in line with other parasitic taxa (e.g. cestodes), which exhibit a similar feeding strategy. We assumed that they feed mainly on metabolites, which were reprocessed by the host and are therefore isotopically lighter. In contrast, the nematodes were enriched in the heavier isotope δ (15)N with respect to their host and the acanthocephalans, respectively. As active feeders they feed on tissues and blood in the body cavity of the host and thus showed isotope discrimination patterns resembling those of

  10. 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.

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Science.gov (United States)

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

    2013-12-01

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

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    Kampouroglou Evdokia E.

    2017-11-01

    Full Text Available 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.

  15. Spontaneous oxygen isotope exchange between carbon dioxide and\

    Czech Academy of Sciences Publication Activity Database

    Knížek, Antonín; Zukalová, Markéta; Kavan, Ladislav; Zukal, Arnošt; Kubelík, Petr; Rojík, P.; Skřehot, P.; Ferus, Martin; Civiš, Svatopluk

    2017-01-01

    Roč. 137, MAR 2017 (2017), s. 6-10 ISSN 0169-1317 R&D Projects: GA MŠk LD14115; GA ČR(CZ) GA14-12010S; GA ČR GA13-07724S; GA MŠk(CZ) LM2015073 Institutional support: RVO:61388955 Keywords : clay * carbon dioxide * FTIR spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.101, year: 2016

  16. Stable isotopes of carbon and nitrogen as markers of dietary variation among sociocultural subgroups of Inuit in Greenland

    DEFF Research Database (Denmark)

    Bjerregaard, Peter; V. L. Larsen, Christina; K. Dahl-Petersen, Inger

    2017-01-01

    OBJECTIVES: We assessed the use of stable isotopes of carbon and nitrogen as biomarkers for traditional versus store-bought food among the Inuit. Furthermore, we compared the isotope patterns among sociocultural population groups. METHODS: As a part of a country-wide health survey in Greenland du...

  17. Variation of carbon isotope fractionation in hydrogenotrophic methanogenic microbial cultures and environmental samples at different energy status

    NARCIS (Netherlands)

    Penning, H.; Plugge, C.M.; Galand, P.E.; Conrad, R.

    2005-01-01

    Methane is a major product of anaerobic degradation of organic matter and an important greenhouse gas. Its stable carbon isotope composition can be used to reveal active methanogenic pathways, if associated isotope fractionation factors are known. To clarify the causes that lead to the wide

  18. The stable isotopic and chemical composition of pedogenic carbonate in the Minusinsk Basin, South Siberia

    Science.gov (United States)

    Vasilchuk, Jessica; Ivanova, Elena; Krechetov, Pavel; Litvinskiy, Vladimir; Budantseva, Nadine; Chizhova, Julia; Vasil'chuk, Yurij

    2017-04-01

    Stable isotope composition of carbonate neoformations can be used as a proxy for the reconstructons of environmental conditions of the past. Carbonate coatings on coarse rock framents are studied in order to indicate the climatic conditions and predominant vegetation under which they were formed. Such coatings commonly occur in different types of soils and paleosols of South Siberian intermountain basins mainly in relatively dry modern conditions. The purpose of the research is to characterize the isotopic composition and chemical composition of carbonate pedofeatures in soils of Minusink Hollow and estimate its correlation with defferent factors. The samples of pedogenic carbonates, vegetation, carbonate parent material, soil water and precipitation water were analyzed using the Delta-V mass spectrometer with options of a gas bench and element analyser. The soils we studied are mainly Kastanozems that are poorly moisturized; therefore, soil pore water was extracted by ethanol. Minor and major elements content was also measured by ICP-MS. Carbonates mostly contain calcuim (37-45%) and highly enriched in Pb, Tl and Ba. Oxygen and carbon isotopic composition of pedogenic carbonates was analyzed in 3 key sites. Kazanovka Khakass state national reserve, Hankul salt lake, region of Sayanogorsk aluminum smelter. Vegetation photosynthetic pathway in the region is mainly C3. δ18O values of carbonate coatings in soils of Kazanovka vary in a range from -7.49 to -10.5‰ (vs V-PDB). The lowest values corresponds the coatings found between two buried mid-Holocene soil horizons. That may indicate cooler conditions of late Holocene than nowadays. In Sayanogorsk carbonates' δ18O values' range is -8.3...-11.1‰ and near the Hankul Lake is -9.0...-10.2‰ all ranges are quite similar and may indicate close conditions of pendants formation. δ13C values of carbonate coatings in Kazanovka vary from -2.5 to -6.7‰, the highest values correspond to the soils of Askiz and Syglygkug

  19. Tracking Seasonal Habitats Using Carbon and Nitrogen Stable Isotopes of Osprey Primary Flight Feathers

    Science.gov (United States)

    Velinsky, D.; Zelanko, P.; Rice, N.

    2011-12-01

    The majority of bird migration studies use the latitudinal precipitation effect of hydrogen and oxygen stable isotopes of feathers to determine wintering and breeding grounds. Few studies have considered carbon and nitrogen stable isotopes to accomplish the same goal; exploiting the variation in dietary constitutes throughout yearly migration cycles. Also, there is no standard procedure of feather sampling; some use body, while others use wing feathers. This sampling discrepancy is not an issue for most migratory species since the majority of birds molt completely in one location, i.e. wintering verse breeding ground. Large birds of prey however, have a continuous molt that may last years, growing feathers on their breeding and wintering grounds. Therefore, a stable isotopic study of Osprey could not randomly sample feathers because it is impossible to know where individual feathers were grown. Here we present an in depth study of carbon and nitrogen stable isotopes from Mid-Atlantic Osprey primary flight feathers. Not only did we observe three signatures indicating the breeding ground and two distinct wintering grounds, we recorded dietary seasonality shifts within 2 to 3 year olds that remain on the wintering grounds for multiple years.

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

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian

    2012-01-01

    In batch experiments, we studied the isotope fractionation in N and O of dissolved nitrate during dentrification. Denitrifying strains Thauera aromatica and “Aromatoleum aromaticum strain EbN1” were grown under strictly anaerobic conditions with acetate, benzoate, and toluene as carbon sources. 18O......-labeled water and 18O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed...... depending on the type of carbon source used. For toluene (ε15N, −18.1 ± 0.6‰ to −7.3 ± 1.4‰; ε18O, −16.5 ± 0.6‰ to −16.1 ± 1.5‰) and benzoate (ε15N, −18.9 ± 1.3‰; ε18O, −15.9 ± 1.1‰) less negative isotope enrichment factors were calculated compared to those derived from acetate (ε15N, −23.5 ± 1.9‰ to −22...

  1. Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

    Science.gov (United States)

    Madigan, M. T.; Takigiku, R.; Lee, R. G.; Gest, H.; Hayes, J. M.

    1989-01-01

    Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

  2. A calcium isotope test of end-Permian ocean acidification using biogenic apatite

    Science.gov (United States)

    Hinojosa, J.; Brown, S. T.; DePaolo, D. J.; Paytan, A.; Shen, S.; Chen, J.; Payne, J.

    2011-12-01

    Submarine erosional truncation of uppermost Permian carbonate strata has been interpreted to reflect ocean acidification coincident with the end-Permian mass extinction. Although this scenario is consistent with carbon isotope and paleontological data, several alternative scenarios, such as ocean overturn or collapse of the biological pump, can also account for the carbon isotope and paleontological evidence. Calcium isotopes provide a geochemical proxy to test between acidification and alternative scenarios. Specifically, a negative shift in the calcium isotope composition (δ44/40Ca) of seawater is predicted under the acidification scenario but not the alternatives. The δ44/40Ca of carbonate rocks from south China exhibits a negative excursion of approximately 0.3%, but this shift could result from either a change in the δ44/40Ca of seawater or a change in carbonate mineralogy because calcite and aragonite exhibit substantially different fractionation factors relative to seawater. To test whether the negative shift in δ44/40Ca reflects seawater δ44/40Ca or carbonate mineralogy, we measured the δ44/40Ca of conodont microfossils (calcium hydroxyapatite) from the global stratotype section for the Permian-Triassic boundary at Meishan, China. The conodont δ44/40Ca record shows a negative excursion similar in stratigraphic position and magnitude to that previously observed in carbonate rocks. Parallel negative excursions in the δ44/40Ca of carbonate rocks and conodont microfossils cannot be accounted for by a change in carbonate mineralogy but are consistent with a negative shift in the δ44/40Ca of seawater. These data add further support for the ocean acidification scenario, pointing toward strong similarities between the greatest catastrophe in the history of animal life and anticipated global change during the 21st century.

  3. Coupled carbon-isotope records from the Cenomanian of SE France: a six-million year record of mid-Cretaceous pCO2 change?

    Science.gov (United States)

    Jarvis, I.; Gröcke, D. R.; Lignum, J.; Trabucho Alexandre, J.; Kennedy, W. J.; Gale, A. S.

    2012-04-01

    corresponding curves from Italy, Germany and England. The δ13Corg curve broadly tracks the carbonate curve with the expected offset of approximately -28 per mil, expressed as the difference between paired isotope values, Δ13C. A marked step increase in Δ13C occurs immediately above a large double positive δ13C excursion at the base of the Middle Cenomanian: Middle Cenomanian Event I. This offset is apparent in both marine and non-marine organic carbon records. The step of +0.5 per mil Δ13C indicates a major change in the global carbon cycle. Could increased isotopic fractionation during Middle and Late Cenomanian times be related to increased pCO2, driven by increased volcanic outgassing on a global scale? We have argued previously that pCO2 peaked during the Late Cenomanian with the emplacement of the Caribbean Large Igneous Province immediately prior to OAE2. Subsequently, the widespread deposition of organic matter caused pCO2 drawdown, evidenced by a sharp fall in Δ13C and cooling, prior to a renewed pCO2 increase and warming in the Early Turonian. Factors influencing δ13Ccarb, δ13Corg and Δ13C trends in the Cenomanian will be discussed in the context of the palaeoceanographic and palaeoclimatic events that accompanied eustatic sea-level change in the earliest Late Cretaceous, culminating in OAE2 and the subsequent global climatic optimum.

  4. 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.

  5. Using stable isotopes of carbon and nitrogen as in-situ tracers for monitoring the natural attenuation of explosives

    National Research Council Canada - National Science Library

    Miyares, Paul H

    1999-01-01

    The use of carbon and nitrogen stable isotope measurements from TNT was examined as a possible tool for monitoring the natural attenuation of TNT incubation studies of spiked soil samples were conducted...

  6. The role of extracellular carbonic anhydrase activity in inorganic carbon utilization of Phaeocystis globosa (Prymnesiophyceae) : A comparison with other marine algae using the isotopic disequilibrium technique

    NARCIS (Netherlands)

    Elzenga, JTM; Prins, HBA; Stefels, J

    The utilization of inorganic carbon species by the marine microalga Phaeocystis globasa (Prymnesiophyceae) and several other algal species from different taxa, was investigated by determining the time course of C-14 incorporation in isotopic disequilibrium experiments. From these kinetic data,

  7. Global Links to Local Carbon Cycling Perturbation

    Science.gov (United States)

    Chen, J.; Montanez, I. P.; Wang, X.; Qi, Y.

    2016-12-01

    Carbon cycle perturbations recorded by stable carbon isotope excursions (CIEs) play an important role in understanding climate, oceanography, and the biosphere through time. Recent studies, however, reveal the influence of regional processes on apparent global CIEs. Deconvolving local/regional from global processes imprinted in the carbon isotopic records of sedimentary successions requires integrated sedimentologic, stratigraphic, and geochemical study. Here we present coupled C and Sr isotopic records of diagenetically screened micrite and brachiopods from late Mississippian shallow-marine, carbonate platform and contemporaneous carbonate slope successions from the east Paleotethys Ocean region (South China). These records reveal distinctly different signatures of the depositional response to the onset of Carboniferous glaciation. C and Sr isotopic compositions of the platform carbonates exhibit systematic fluctuations in step with inferred sea-level changes captured by depositional cycles. CIEs in the platform succession can be correlated to the contemporaneous C isotope record from the Antler carbonate ramp (Idaho, USA). In contrast, slope carbonate and conodont isotopic records exhibit minimal variability interpreted to record the open-ocean seawater composition. The isotopic disparity between successions is interpreted to record the influence of local depositional, but not diagenetic, processes operating on the carbonate platform in response to glacioeustasy. Variability in the nature of coupled isotopic and inferred sea level fluctuations is interpreted to record stepwise onset of the late Paleozoic ice age in the late Mississippian. Initial large magnitude shifts in C and Sr isotopic compositions of late Visean to early Serpukhovian carbonates correspond to 1 to 2 myr-scale cycles driven by the buildup of continental glaciers. Subsequent decreased magnitude of isotopic shifts coincident with a shift to shorter duration and smaller magnitude sea

  8. Carbon Isotope Composition of Mysids at a Terrestrial-Marine Ecotone, Clayoquot Sound, British Columbia, Canada

    Science.gov (United States)

    Mulkins, L. M.; Jelinski, D. E.; Karagatzides, J. D.; Carr, A.

    2002-04-01

    The relative contribution of summertime terrestrial versus marine carbon to an estuary on coastal British Columbia, Canada was explored using stable carbon isotopic (δ 13C values) analysis of mysid crustaceans (Malacostraca: Peracarida: Mysidacea). We hypothesized that landscape linkages between the forested upland and adjacent inshore marine waters, via river, groundwater and overland flows, may influence carbon content and metabolism in the coastal zone. We sampled 14 stations spatially distributed in a grid and found δ 13C compositions of mysids ranged from -15·2 to -18·4‰. There was, however, no obvious spatial distribution of δ 13C values relative to the estuarine gradient in Cow Bay. Heavy tidal mixing is suggested to disperse marine and terrestrial carbon throughout the entire bay. From a temporal perspective however, mysid δ 13C signatures became enriched over the sampling period (mid-July to mid-August), which is representative of a stronger marine influence. This may arise because mysids are exposed to greater marine-derived carbon sources later in the summer, a decrease in freshwater input (and hence terrestrial carbon), changes in phytoplankton or macrophyte community structure, or that mysids preferentially feed on marine food sources. Overall, the recorded isotopic values are characteristic of marine organic carbon signatures suggesting that in summer, despite the proximity to shore, little or no terrestrial carbon penetrates the food web at the trophic level of mysids. This notwithstanding we believe there is a strong need for additional study of carbon flows at the marine-terrestrial interface, especially for disturbed watersheds.

  9. Analytical Method for Carbon and Oxygen Isotope of Small Carbonate Samples with the GasBench Ⅱ-IRMS Device

    Directory of Open Access Journals (Sweden)

    LIANG Cui-cui

    2015-01-01

    Full Text Available An analytical method for measuring carbon and oxygen isotopic compositions of trace amount carbonate (>15 μg was established by Delta V Advantage isotope Ratio MS coupled with GasBench Ⅱ. Different trace amount (5-50 μg carbonate standard samples (IAEA-CO-1 were measured by GasBench Ⅱ with 12 mL and 3.7 mL vials. When the weight of samples was less than 40 μg and it was acidified in 12 mL vials, most standard deviations of the δ13C and δ18O were more than 0.1‰, which couldn’t satisfied high-precision measurements. When the weight of samples was greater than 15 μg and it was acidified in 3.7 mL vials, standard deviations for the δ13C and δ18O were 0.01‰-0.07‰ and 0.01‰-0.08‰ respectively, which satisfied high-precision measurements. Therefore, small 3.7 mL vials were used to increase the concentration of carbon dioxide in headspace, carbonate samples even less as 15 μg can be analyzed routinely by a GasBench Ⅱ continuous-flow IRMS. Meanwhile, the linear relationship between sample’s weight and peak’s area was strong (R2>0.993 2 and it can be used to determine the carbon content of carbonate samples.

  10. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate: Implications for their use as paleoclimatic proxy

    Science.gov (United States)

    Rodler, A.; Sánchez-Pastor, N.; Fernández-Díaz, L.; Frei, R.

    2015-09-01

    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 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 of chromate into the calcite lattice to investigate isotopic changes facilitated by the coprecipitation process. Our experiments indicate enrichment in Cr concentration in the precipitates compared to the solutions, consistent with previous reports of Cr enrichment in chemical sediments compared to ambient seawater. The fractionation of Cr isotopes during calcium carbonate coprecipitation was assumed to be small, based on previously published data of modern seawater and modern non-skeletal marine carbonates. However, results from this study for rapidly precipitated calcium carbonate in the presence of chromate show a tendency for preferential incorporation of heavy Cr isotopes in the precipitates resulting in increasing relative isotope difference between precipitate and initial solution (Δ53Cr[p-is]) from +0.06‰ to +0.18‰, with increasing initial Cr concentration of the solution. Sample precipitation in the presence of chromate also showed the presence of vaterite. Calcium carbonate crystals were also precipitated in a double diffusion silica hydrogel over a longer period of time resulting in samples consisting of micrometric-millimetric calcite crystals, which were again significantly enriched in heavy Cr isotopes compared to the initial solutions. They average, irrespective of the initial Cr concentration, a relative isotope difference (Δ53Cr[p-is]) of +0.29 ± 0.08‰ (2σ), whereas

  11. 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

  12. Salinity of the Early and Middle Eocene Arctic Ocean From Oxygen Isotope Analysis of Fish Bone Carbonate

    Science.gov (United States)

    Waddell, L. M.; Moore, T. C.

    2006-12-01

    Plate tectonic reconstructions indicate that the Arctic was largely isolated from the world ocean during the early and middle Eocene, with exchange limited to shallow, and possibly intermittent, connections to the North Atlantic and Tethys (via the Turgay Strait). Relative isolation, combined with an intensification of the hydrologic cycle under an Eocene greenhouse climate, is suspected to have led to the development of a low- salinity surface water layer in the Arctic that could have affected deep and intermediate convection in the North Atlantic. Sediment cores recently recovered from the Lomonosov Ridge by the IODP 302 Arctic Coring Expedition (ACEX) allow for the first assessment of the salinity of the Arctic Ocean during the early and middle Eocene. Stable isotope analysis performed on the structural carbonate of fish bone apatite from ~30 samples between the ages of ~55 and ~44 myr yielded δ18O values between -6.84‰ and -2.96‰ VPDB, with a mean value of -4.89‰. From the δ18O values we calculate that the Arctic Ocean was probably brackish during most of the early and middle Eocene, with an average salinity of 19 to 24‰. Negative excursions in the δ18O record (<-6‰) indicate three events during which the salinity of the Arctic surface waters was severely lowered: the Paleocene Eocene Thermal Maximum (PETM), the Azolla event at ~49 Ma, and a third previously unidentified event at ~46 Ma. During the PETM, low salinities developed under conditions of increased regional precipitation and runoff associated with extreme high latitude warmth and possible tectonic uplift in the North Atlantic. During the other two low-salinity events, sea level was lowered by ~20-30 m, implying a possible severing of Arctic connections to the world ocean. The most positive δ18O value (-2.96‰) occurs at ~45 Ma, the age of the youngest dropstone discovered in the ACEX sediments, and may therefore correspond to a climatic cooling rather than a high salinity event.

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

    Science.gov (United States)

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

    2017-06-01

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

  14. Carbon Isotope Environmental Forensics: Fingerprinting Gas From Domestic Water Wells From petroleum Fields of Alberta, Canada

    Science.gov (United States)

    Muehlenbachs, K.; Tilley, B.

    2008-12-01

    Sixty years of petroleum development has resulted in over 500,000 petroleum wells drilled in the Western Canada Sedimentary Basin, many in agricultural areas that rely on groundwater (GW). The impact on GW quality by petroleum development is increasingly becoming a societal and regulatory concern triggered by intensive, recent CBM development. To protect GW the production tubing of a resource well is encased by a larger diameter surface casing (SCV) that is set deeper than the depth of potable water. Because of poor cementing the SCVs and soils near the wells often contain gas heightening concern for integrity of GW. Carbon isotope analyses of thousands of SCV gases shows them only rarely to be sourced from the target zone of the resource well, but rather from an intermediate depth. It has long been known that many water wells produce methane and traces of ethane and it needs to be determined if the water wells have been impacted. Alberta now requires all water wells to be tested prior to drilling of nearby resource wells. Carbon isotope analyses are mandated on a proportion of all gases produced by water wells and many hundreds of gas analyses will be placed in a public data base. Carbon isotope values of gases vary within the basin and can be used to quantify natural gas contamination of GW. Two case studies will be presented where landowners have filed complaints about gas contamination of their water wells. Attributing specific contaminant sources to a given resource well has proven to be difficult in areas where there is ongoing CBM development. However, in one area, the problem gas can be attributed to previous conventional petroleum development rather than the current CBM drilling and production. Carbon isotope analyses of water wells in another area suggest a few per cent of CBM contamination in water wells. Unfortunately, lack of pre-drilling background water data prevents reliable quantification of the contamination.

  15. Compositional and stable carbon isotopic fractionation during non-autocatalytic thermochemical sulfate reduction by gaseous hydrocarbons

    Science.gov (United States)

    Xia, Xinyu; Ellis, Geoffrey S.; Ma, Qisheng; Tang, Yongchun

    2014-01-01

    The possibility of autocatalysis during thermochemical sulfate reduction (TSR) by gaseous hydrocarbons was investigated by examination of previously reported laboratory and field data. This reaction was found to be a kinetically controlled non-autocatalytic process, and the apparent lack of autocatalysis is thought to be due to the absence of the required intermediate species. Kinetic parameters for chemical and carbon isotopic fractionations of gaseous hydrocarbons affected by TSR were calculated and found to be consistent with experimentally derived values for TSR involving long-chain hydrocarbons. Model predictions based on these kinetic values indicate that TSR by gaseous hydrocarbon requires high-temperature conditions. The oxidation of C2–5 hydrocarbons by sulfate reduction is accompanied by carbon isotopic fractionation with the residual C2–5 hydrocarbons becoming more enriched in 13C. Kinetic parameters were calculated for the stable carbon isotopic fractionation of gaseous hydrocarbons that have experienced TSR. Model predictions based on these kinetics indicate that it may be difficult to distinguish the effects of TSR from those of thermal maturation at lower levels of hydrocarbon oxidation; however, unusually heavy δ13C2+ values (>−10‰) can be diagnostic of high levels of conversion (>50%). Stoichiometric and stable carbon isotopic data show that methane is stable under the investigated reaction conditions and is likely a product of TSR by other gaseous hydrocarbons rather than a significant reactant. These results indicate that the overall TSR reaction mechanism for oxidation of organic substrates containing long-chain hydrocarbons involves three distinct phases as follows: (1) an initial slow and non-autocatalytic stage characterized by the reduction of reactive sulfate by long-chain saturated hydrocarbons; (2) a second autocatalytic reaction phase dominated by reactions involving reduced sulfur species and partially oxidized hydrocarbons; (3

  16. Stable carbon isotope fractionation in the search for life on early Mars

    Science.gov (United States)

    Rothschild, L. J.; Desmarais, D.

    1989-01-01

    The utility of measurements of C-13/C-12 ratios in organic vs inorganic deposits for searching for signs of life on early Mars is considered. It is suggested that three assumptions are necessary. First, if there was life on Mars, it caused the fractionation of carbon isotopes in analogy with past biological activity on earth. Second, the fractionation would be detectable. Third, if a fractionation would be observed, there exist no abiotic explanations for the observed fractionation pattern.

  17. Reaction cross sections of proton scattering from carbon isotopes (A=8-22) by means of the relativistic impulse approximation

    Science.gov (United States)

    Kaki, Kaori

    2017-09-01

    Reaction cross sections of carbon isotopes for proton scattering are calculated in a large energy region. Density distributions of carbon isotopes are obtained from relativistic mean-field results. Calculations are based on the relativistic impulse approximation, and results are compared with experimental data. A strong relationship between reaction cross section and root-mean-square radius is clearly shown for ^{12}C using a model distribution.

  18. Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, M.; Mohan, R.; Meloth, T.; Naik, S.S.; Sudhakar, M.

    SCIENCE, VOL. 100, NO. 6, 25 MARCH 2011 881 *For correspondence. (e-mail: manish@ncaor.org) Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean Manish Tiwari 1...: Carbon isotopes, foraminifera, oxygen iso- topes, Southern Ocean. PLANKTIC foraminifera thrive in various environments of the upper water column and are sensitive to changes occurring in the temperature, salinity, nutrients, food availability...

  19. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Directory of Open Access Journals (Sweden)

    Thomas Larsen

    Full Text Available Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13C patterns among amino acids (δ(13CAA could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13CAA patterns in contrast to bulk δ(13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs.

  20. Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)

    Science.gov (United States)

    Vigier, Nathalie; Rollion-Bard, Claire; Levenson, Yaël; Erez, Jonathan

    2015-01-01

    Past ocean pH and pCO2 are critical parameters for establishing relationships between Earth's climate and the carbon cycle. Previous pCO2 estimates are associated with large uncertainties and are debated. In this study, laboratory cultures of the foraminiferan genus Amphistegina were performed in order to examine the possible factors that control the Li isotope composition (δ7Li) of their shells. δ7Li is insensitive to temperature and pH variations but correlates positively with the Dissolved Inorganic Carbon (DIC) of seawater. Li/Ca ratio in the shells shows negative correlation with δ7Li, consistent with published data for planktonic foraminifera from core tops and from short periods during the Cenozoic. We propose that the sensitivity of δ7Li and Li/Ca ratio to DIC is a biological phenomenon and is related to biomineralization mechanisms in foraminifera. We used the published foraminiferal δ7Li records, and our experimental results, to determine the paleo-ocean DIC and pH for the last glacial-interglacial cycle. The results are consistent with published estimates of pH and pCO2 based on boron isotopes and ice cores. We suggest Li and its isotopes may serve as a new complementary proxy for the paleo-ocean carbonate chemistry.

  1. Effects of volatilization on carbon and hydrogen isotope ratios of MTBE.

    Science.gov (United States)

    Kuder, Tomasz; Philp, Paul; Allen, Jon

    2009-03-15

    Contaminant attenuation studies utilizing CSIA (compound-specific isotope analysis) routinely assume that isotope effects (IEs) result only from degradation. Experimental results on MTBE behavior in diffusive volatilization and dynamic vapor extraction show measurable changes in the isotope ratios of the MTBE remaining in the aqueous or nonaqueous phase liquid (NAPL) matrix. A conceptual model for interpretation of those IEs is proposed, based on the physics of liquid-air partitioning. Normal or inverse IEs were observed for different volatilization scenarios. The range of carbon enrichment factors (epsilon) was from +0.7 per thousand (gasoline vapor extraction) to -1 per thousand (diffusive volatilization of MTBE from gasoline), the range of hydrogen epsilon was from +7 per thousand (gasoline vapor extraction) to -12 per thousand (air sparging of aqueous MTBE). The observed IEs are lower than those associated with MTBE degradation. However, under a realistic scenario for MTBE vapor removal, their magnitude is within the detection limits of CSIA. The potential for interference of those IEs is primarily in confusing the interpretation of samples with a small extent of fractionation and where only carbon CSIA data are available. The IEs resulting from volatilization and biodegradation, respectively, can be separated by combined carbon and hydrogen 2D-CSIA.

  2. Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

    Directory of Open Access Journals (Sweden)

    Sonja Cerar

    2013-01-01

    Full Text Available Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1 Ljubljansko polje aquifer, with higher Ca2+ values, as limestone predominates in its recharge area, (2 northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3 central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4 Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.

  3. STRONTIUM ISOTOPE STRATIGRAPHY AS A CONTRIBUTION FOR DATING MIOCENE SHELF CARBONATES (S. MARINO FM., NORTHERN APENNINES

    Directory of Open Access Journals (Sweden)

    CLAUDIO ARGENTINO

    2017-01-01

    Full Text Available This paper provides new data on strontium isotope stratigraphy applied to the Miocene heterozoan shelfal carbonates of the S. Marino Fm. (Marecchia Valley, northern Apennines. Sr isotopic analyses were carried out on oyster shells, bryozoans and bulk-rocks from the lower-middle carbonate portion of the section. In the upper part of the succession that shows evidence of detrital influx,87Sr/86Sr analyses were performed on foraminifera tests, separating planktonic and benthic forms. Results were compared with calcareous nannofossil biostratigraphic data from the same levels, in order to test the reliability of Sr dating in mixed carbonate-siliciclastic sediments. Mean ages obtained from oysters range between 16.9 Ma and 16.3 Ma. Very similar results are obtained using bryozoans (16.5 Ma to 16.1 Ma and bulk-rocks (16.8 Ma to 16.2 Ma. These results allow to better constrain the age of the massive carbonate shelf, referable to the upper Burdigalian. In the upper carbonate-siliciclastic portion of the shelf, numerical ages obtained from planktonic and benthic foraminifera are in good agreement with nannofossil biozones (mean ages respectively around 15.3 Ma and 14.5 Ma although they display wide confidence intervals. These wide age uncertainties depend on the slow rate of change of marine 87Sr/86Sr through time that characterizes the interval between ~15 and ~13.5 Ma.

  4. Mechanisms controlling the carbon stable isotope composition of phytoplankton in karst reservoirs

    Directory of Open Access Journals (Sweden)

    Baoli Wang

    2013-02-01

    Full Text Available In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHYin freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton which assimilated more dissolved inorganic carbon (DIC, resulting in the increase of δ13CPHY, δ13CDIC and pH. When the concentration of dissolved carbon dioxide (CO2 was less than 10 mmol L–1, phytoplankton shifted to using HCO3– as a carbon source. This resulted in the sharp increase of δ13CPHY. The carbon stable isotope composition of phytoplankton tended to decrease with the increase of Bacillariophyta, which dominated in January and April, but tended to increase with the increase of Chlorophyta and Dinophyta, which dominated in July. Multiple regression equations suggested that the influence of biological factors such as taxonomic difference on δ13CPHY could be equal or more important than that of physical and chemical factors. Thus, the effect of taxonomic differences on δ13CPHY must be considered when explaining the δ13C of organic matter in lacustrine ecosystem.

  5. Isotopically Light Organic Carbon in Phanerozoic Black Shales: Diagenetic, Source, or Environmental Signal?

    Science.gov (United States)

    Meyers, P. A.

    2011-12-01

    A curious depletion of 13C in the organic matter of marine black shales has been widely recognized ever since the advent of carbon isotope measurements half a century ago. Paleozoic and Mesozoic black shales commonly have del13C values between -29 and -26 permil, whereas modern marine organic matter has values between -22 and -18 permil. The black shale values mimic those of continental organic matter, yet sedimentary settings and Rock-Eval results indicate that the organic matter is marine in origin. This presentation will overview and discuss hypotheses to explain the isotopically light values of the black shales. First, the preferential removal of isotopically heavier organic matter components such as carbohydrates by diagenesis will be examined and shown to be wanting. Second, the possible oxidation of isotopically light methane released from clathrates that would have altered the DIC pool available to phytoplankton will be considered and also be found unlikely. A third possibility - that greater concentrations of CO2 in the greenhouse atmospheres that corresponded with deposition of many black shales allowed greater discrimination against 13C during photosynthesis - will be evaluated from del13C values of bulk carbon and of algal and land-plant biomarker molecules. Finally, the possibility that stronger stratification of the surface ocean may have magnified photic zone recycling of organic matter and reincorporation of its isotopically light carbon into fresh biomass will be considered. Although the fourth possibility is contrary to the conditions of vertical mixing of nutrients that exist in modern upwelling systems and that are responsible for their high productivity, it is consistent with the strongly stratified conditions that accompanied the high productivity that produced the Pliocene-Pleistocene sapropels of the Mediterranean Sea. Because the sapropels and most Phanerozic black shales share del15N values near 0 permil, nitrogen fixation evidently was

  6. Stable carbon isotope ratios in Astrangia danae : evidence for algal modification of carbon pools used in calcification

    Science.gov (United States)

    Cummings, C. E.; McCarty, H. B.

    1982-06-01

    Stable carbon isotope ratios have been measured in skeletons of the temperature shallow water scleractinian coral, Astrangia danae. δ13C values ranging from -5.42 to -7.30%. revealed the expected depletion of 13C in skeletal carbonate relative to sea water bicarbonate. Differences among the ratios could not be attributed to collection site and were not correlated to skeletal morphology. Values of δ13C were directly related to zooxanthellae density for all colonies, so that as zooxanthellae concentration increased, δ13C valued increased. Colonies maintained under high temperature conditions were offset from the normal, exhibiting ratios less enriched in 13C than similar colonies from natural conditions. These trends supported the models of Weber and Goreau in which the carbon pools used in calcification are modified by algal photosynthesis. Direct evidence of physiological differences between symbiotic and asymbiotic colonies of A. danae has also been provided.

  7. Stable isotopic composition of pedogenic carbonate in soils of Minusinsk Hollow

    Science.gov (United States)

    Vasil'chuk, Jessica; Krechetov, Pavel; Budantseva, Nadine; Chizhova, Julia; Vasil'chuk, Yurij

    2016-04-01

    The purpose of the research is to characterize the isotopic composition of carbonate neoformations in soils and estimate its correlation with isotopic composition of water and parent material. The study site is located in the Minusinsk Hollow that is situated among Kuznetsk Alatau and Sayan Mountains. Three key-sites with in different parts of hollow, under mainly steppe vegetation with calciphilic grasses and diverse parent material were studied including: 1) Kazanovka Khakass state national reserve in foothills of Kuznetsk Alatau 2) Hankul salt lake that is considered as natural monument 3) region of Sayanogorsk aluminum smelter on a left bank of the Yenisei river. The samples of pedogenic and lithogenic carbonates as well as water samples were analyzed using the Delta-V mass spectrometer with a standard option of a gas bench according to standard methods. Carbonate coatings (also called pendants or cutans) is one of the most common types of carbonate neoformations occurring in the region. Fine coatings' layers one over another usually can be found on the bottom sides of rubble and gravel inside the soil profile colour varies from white to brownish and yellowish (probably depending on the impurities of organic matter). In Petric Calcisols, Chernozems and Kastanozems δ18O values of coatings vary in a rather small range from - 8.9 to - 10.1 ‰ PDB. This probably shows that their forming took place approximately in the same climatic conditions. While δ18O values of carbonate parent rocks are close to them and are vary from - 11.1 to - 11.9 ‰ PDB. Also, δ13C values of coatings strongly decrease from inner (older) to outer (younger) layers, that can indicate differences connected with the diffusion of organic material. River waters' δ18O values also show a small range from - 16.62 to - 17.66‰ SMOW, while salt lakes' waters due to the fractionation evaporation effects demonstrate much heavier values from - 4.73 to - 9.22‰ SMOW. The groundwater shows δ18O

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

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-11-01

    In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E) in East Asia, total suspended particles (TSP) were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during pollen emission episodes (range: -26.2‰ to -23.5‰, avg. -25.2 ± 0.9‰), approaching those of the airborne pollen (-28.0‰) collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C). Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

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

    Directory of Open Access Journals (Sweden)

    J. Jung

    2011-11-01

    Full Text Available In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E in East Asia, total suspended particles (TSP were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC, total nitrogen (TN, and stable carbon isotopic composition (δ13C of TC. The stable carbon isotopic composition of TC (δ13CTC was found to be lowest during pollen emission episodes (range: −26.2‰ to −23.5‰, avg. −25.2 ± 0.9‰, approaching those of the airborne pollen (−28.0‰ collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C. Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

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

    Science.gov (United States)

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

    2015-07-15

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

  11. Fatty acid and stable carbon isotope characterization of Camelina sativa oil: implications for authentication.

    Science.gov (United States)

    Hrastar, Robert; Petrisic, Marinka G; Ogrinc, Nives; Kosir, Iztok Joze

    2009-01-28

    The importance of authenticity characterization is an increasing and pressing requirement for all foods. Vegetable oil is one of the most studied foods because of its nutritional and medicinal properties in a correct diet. In this study, a total of 53 Camelina sativa samples, from all known growing areas, were chemically and isotopically characterized. The fatty acid content of camelina oil was determined by gas chromatography (GC), and the ratios of stable carbon isotopes ((13)C/(12)C) of individual fatty acids and seed/bulk oil were determined by gas chromatography-combustion-stable isotope ratio mass spectrometry (GC/C/IRMS) and elemental analysis-stable isotope ratio mass spectrometry (IRMS). A total of 17 different fatty acids were detected by GC, with omega3 R-linolenic acid (C(18:3n3)) being the most abundant (29.7-40.0 wt %). Oleic acid (C(18:1n9)), linoleic acid (C(18:2n6)) and eicosenoic acid (C(20:1n9)) all belong to the second group of major fatty acids. The stable carbon isotopic values (delta(13)C) fell into a range typical for C(3) plants. The use of delta(13)C(18:2n6) vs delta(13)C(18:3n3) correlation could show cases where impurity or adulteration is suspected, whereas principal component analysis clearly separates oil samples from different continents. Preliminary results on the camelina oil authentication procedure provide a basis for the investigation of geographical origin and the further distinction between camelina and camelina refined or other, less expensive oils.

  12. Autonomous excursions using tablets and smartphones

    Science.gov (United States)

    Marra, Wouter; Groothengel, Marin; van de Grint, Liesbeth; Karssenberg, Derek; Stouthamer, Esther

    2017-04-01

    Excursions and fieldworks are valuable components for geosciences education. However, field activities can be time consuming for teachers and pose a logistical challenge to fit in regular courses. Furthermore, the participation of students diminishes with group size in case of instructor-led outings. We are developing excursions that students can follow autonomously without a teacher present, using instructions, assignments and background information on tablets and smartphones. The goal of this approach is to increase the level of active participation, and to reduce logistical and time table issues. We developed a bike-excursion about the landscape and geology in the vicinity of our University. Such excursion was on the wish-list for several years, but posed a logistical challenge for the group of about 80 students in the available timeslot. In our approach, students had a time-window of two weeks in which they could finish the excursion in groups of 2. 8-Inch tablets with water- and shock-proof cases were available for this excursion. For the excursion we used three apps: 1) IZI-Travel for providing the route, spoken navigation instructions, spoken explanations at stops, location-related images, assignments as text, and multiple-choose questions. 2) PDF-Maps for providing geo-referenced maps. 3) ESRI Collector which the students used to digitize polygons on a map, and to collect geo-referenced photos with explanation. These data were answers to assignments and were later used in a tutorial on campus. The assignments where students had to collect data, and the small group size (pairs) increased the level of active participation. The use of a final tutorial on campus was important for the autonomous excursion, as it gave students the opportunity to discuss their observations and questions with their teacher. The developed teaching materials are available online to use and adapt for others. Parts could be useful for other universities and schools in the vicinity of

  13. Application of Nitrogen and Carbon Stable Isotopes ([delta]15N and [delta]13C) to Quantify Food Chain Length and Trophic Structure

    National Research Council Canada - National Science Library

    Matthew J Perkins; McDonald, Robbie; Veen, J; Kelly, Simon; Rees, Gareth; Bearhop, Stuart

    2014-01-01

      Increasingly, stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures...

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

    Science.gov (United States)

    McMahon, K. W.; Berumen, M. L.; Mateo, I.; Elsdon, T. S.; Thorrold, S. R.

    2011-12-01

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

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

    Science.gov (United States)

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

    2016-11-01

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

  16. 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.

  17. Stable isotopes of carbon dioxide in soil gas over massive sulfide mineralization at Crandon, Wisconsin

    Science.gov (United States)

    Alpers, C.N.; Dettman, D.L.; Lohmann, K.C.; Brabec, D.

    1990-01-01

    Stable isotope ratios of oxygen and carbon were determined for CO2 in soil gas in the vicinity of the massive sulfide deposit at Crandon, Wisconsin with the objective of determining the source of anomalously high CO2 concentrations detected previously by McCarthy et al. (1986). Values of ??13C in soil gas CO2 from depths between 0.5 and 1.0 m were found to range from -12.68??? to -20.03??? (PDB). Organic carbon from the uppermost meter of soil has ??13C between -24.1 and -25.8??? (PDB), indicating derivation from plant species with the C3 (Calvin) type of photosynthetic pathway. Microbial decomposition of the organic carbon and root respiration from C3 and C4 (Hatch-Slack) plants, together with atmospheric CO2 are the likely sources of carbon in soil gas CO2. Values of ??18O in soil-gas CO2 range from 32 to 38??? (SMOW). These ??18O values are intermediate between that calculated for CO2 gas in isotopic equilibrium with local groundwaters and that for atmospheric CO2. The ??18O data indicate that atmospheric CO2 has been incorporated by mixing or diffusion. Any CO2 generated by microbial oxidation of organic matter has equilibrated its oxygen isotopes with the local groundwaters. The isotopic composition of soil-gas CO2 taken from directly above the massive sulfide deposit was not distinguishable from that of background samples taken 1 to 2 km away. No enrichment of the ??13C value of soil-gas CO2 was observed, contrary to what would be expected if the anomalous CO2 were derived from the dissolution of Proterozoic marine limestone country rock or of Paleozoic limestone clasts in glacial till. Therefore, it is inferred that root respiration and decay of C3 plant material were responsible for most CO2 generation both in the vicinity of the massive sulfide and in the "background" area, on the occasion of our sampling. Interpretation of our data is complicated by the effects of rainfall, which significantly reduced the magnitude of the CO2 anomaly. Therefore, we cannot

  18. 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.

  19. Effects of caloric restriction on nitrogen and carbon stable isotope ratios in adult rat bone.

    Science.gov (United States)

    Robertson, Kimberly L; Rowland, Neil E; Krigbaum, John

    2014-10-15

    Stable isotope analysis is a valuable technique for dietary estimation in ecological and archaeological research, yet many variables can potentially affect tissue stable isotope signatures. Controlled feeding studies across a range of species have consistently demonstrated impacts of caloric restriction on tissue stable isotope ratios, but most have focused on juvenile, fasting, and/or starving individuals, and most have utilized soft tissues despite the importance of bone for paleodietary analyses. The goal of this study was to determine whether temporally defined, moderate food restriction could affect stable carbon and/or nitrogen isotope ratios in adult mammalian bone - a tissue that arguably reflects long-term dietary signals. Adult rats fed a standard laboratory diet were restricted to 45% of ad libitum intakes for 3 or 6 months. Relevant anatomical and physiological parameters were measured to confirm that the restriction protocol resulted in significant nutritional stress and to provide independent data to facilitate interpretation of stable isotope ratios. Femoral bone δ(13)Ccollagen, δ(15)Ncollagen, and δ(13)Capatite values were determined by isotope ratio mass spectrometry. Calorie-restricted animals exhibited a small, yet significant enrichment in (15)Ncollagen compared with control animals, reflecting protein-calorie stress. While the δ(13)Ccollagen values did not differ, the δ(13)Capatite values revealed less enrichment in (13)C than in controls, reflecting catabolism of body fat. Independent anatomical and physiological data from these same individuals support these interpretations. Results indicate that moderate caloric restriction does not appreciably undermine broad interpretations of dietary signals in adult mammalian bone. Significant variability among individuals or groups, however, is best explained by marked differences in energy intake over variable timescales. An inverse relationship between the δ(13)Capatite and δ(15)Ncollagen

  20. 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.

  1. Improved method for isotopic and quantitative analysis of dissolved inorganic carbon in natural water samples.

    Science.gov (United States)

    Assayag, Nelly; Rivé, Karine; Ader, Magali; Jézéquel, Didier; Agrinier, Pierre

    2006-01-01

    We present here an improved and reliable method for measuring the concentration of dissolved inorganic carbon (DIC) and its isotope composition (delta(13)C(DIC)) in natural water samples. Our apparatus, a gas chromatograph coupled to an isotope ratio mass spectrometer (GCIRMS), runs in a quasi-automated mode and is able to analyze about 50 water samples per day. The whole procedure (sample preparation, CO(2(g))-CO(2(aq)) equilibration time and GCIRMS analysis) requires 2 days. It consists of injecting an aliquot of water into a H(3)PO(4)-loaded and He-flushed 12 mL glass tube. The H(3)PO(4) reacts with the water and converts the DIC into aqueous and gaseous CO(2). After a CO(2(g))-CO(2(aq)) equilibration time of between 15 and 24 h, a portion of the headspace gas (mainly CO(2)+He) is introduced into the GCIRMS, to measure the carbon isotope ratio of the released CO(2(g)), from which the delta(13)C(DIC) is determined via a calibration procedure. For standard solutions with DIC concentrations ranging from 1 to 25 mmol . L(-1) and solution volume of 1 mL (high DIC concentration samples) or 5 mL (low DIC concentration samples), delta(13)C(DIC) values are determined with a precision (1sigma) better than 0.1 per thousand. Compared with previously published headspace equilibration methods, the major improvement presented here is the development of a calibration procedure which takes the carbon isotope fractionation associated with the CO(2(g))-CO(2(aq)) partition into account: the set of standard solutions and samples has to be prepared and analyzed with the same 'gas/liquid' and 'H(3)PO(4)/water' volume ratios. A set of natural water samples (lake, river and hydrothermal springs) was analyzed to demonstrate the utility of this new method.

  2. Palynology and Carbon isotope stratigraphy of the Triassic - Jurassic transition in the Salt Range (Pakistan)

    Science.gov (United States)

    Kuerschner, Wolfram Michael; Iqbal, Shahid; Wagreich, Michael; Jan, Irfan; Gier, Susanne

    2017-04-01

    The Triassic Jurassic transition is characterized by enhanced rates of biotic turnover in the marine and terrestrial realms. Negative C isotope anomalies have been reported that may indicate coeval disturbances in the biogeochemical cycles. However, most data are collected from sections located in the northern hemisphere. We present preliminary results of an integrated study on the palynology and the Carbon isotope composition of bulk sedimentary organic matter from a TJ section in the Salt Range (Pakistan). The studied Tethyan Salt Range sections consist of a succession of dolomites/green-black shales (Kingriali Formation) which is followed by a series of quartzose sandstone, shales, laterites and conglomerates/pebbly sandstones (Datta Formation). The shales of the Kingriali Formation yield well preserved palynomorph assemblages dominated by diverse bisccate pollen. Also prasinophytes (green algae) are common indicating a marine depositional environment. Of note is the presence of the dinoflagellate cysts Rhaetogonyaulax, Suessia and Baumontella which indicate a Rhaetian age for the Kingriali Formation. The continental siliciclastics which follow on top of the dolomites yield spore dominated assemblages. The first occurrence of Cerebropollenites thiergatii indicates the approximate position of the base of the Hettangian. Higher up in the section pollen assemblages from the shales of the Datta Formation yield monotonous pollen assemblages dominated by Classopollis turosus. While most samples analyzed for Carbon isotopes showed values around -25 permil only the shales of the uppermost Kingriali Formation show significant more negative values of about -30 permil. The established Carbon isotope record and palynostratigraphic events and their correlation with other TJ boundary sections will be discussed. Our results suggest a rather complete sedimentary record of the Triassic - Jurassic boundary in the studied Salt Range sections.

  3. Molecular isotopic engineering (MIE): industrial manufacture of naproxen of predetermined stable carbon-isotopic compositions for authenticity and security protection and intellectual property considerations

    Science.gov (United States)

    Jasper, J. P.; Farina, P.; Pearson, A.; Mezes, P. S.; Sabatelli, A. D.

    2016-05-01

    Molecular Isotopic Engineering (MIE) is the directed stable-isotopic synthesis of chemical products for reasons of product identification and of product security, and also for intellectual property considerations. We report here a generally excellent correspondence between the observed and predicted stable carbon-isotopic (δ13C) results for a successful directed synthesis of racemic mixture from its immediate precursors. The observed results are readily explained by the laws of mass balance and isotope mass balance. Oxygen- and hydrogen isotopic results which require an additional assessment of the effects of O and H exchange, presumably due to interaction with water in the reaction solution, are addressed elsewhere. A previous, cooperative study with the US FDA-DPA showed that individual manufacturers of naproxen could readily be differentiated by their stable-isotopic provenance (δ13C, δ18O, and δD ref. 1). We suggest that MIE can be readily employed in the bio/pharmaceutical industry without alteration of present manufacturing processes other than isotopically selecting and/or monitoring reactants and products.

  4. Carbon and Nitrogen Stable Isotope Values for Plants and Mammals in a Semi-Desert Region of Mongolia

    Directory of Open Access Journals (Sweden)

    Hannah Davie

    2014-12-01

    Full Text Available Little information exists on the isotopic signatures of plants and animals in Mongolia, limiting the application of stable isotope analysis to wildlife biology studies. Here we present plant and mammal carbon (δ 13 C and nitrogen (δ 15 N isotope values from a desert-steppe region of southeastern Mongolia. We analyzed 11 samples from 11 plant species and 93 samples from 24 mammal species across Ikh Nart Nature Reserve, and compared these numbers to isotope values reported from other areas of Mongolia. Our plant and mammal 13 C and 15 N values were similar to those from a similar arid steppe region and more enriched than those from less arid habitats. Habitat variation within and between study sites has an important infl uence on δ 13 C and δ 15 N variation. Our results supplement current knowledge of isotopic variation in Mongolia and provide a reference for future stable isotope research in Mongolia and similar Asian steppe ecosystems.

  5. Enhanced productivity rather than enhanced preservation led to increased organic carbon burial in the euxinic southern proto North Atlantic Ocean during the Cenomanian/Turonian Oceanic Anoxic Event

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Kuypers, M.M.M.; Pancost, R.D.; Nijenhuis, I.A.

    2002-01-01

    Three Cenomanian/Turonian (C/T, ∼93.5 Ma) black shale sections along a northeast-southwest transect in the southern part of the proto-North Atlantic Ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in δ¹³C values of both bulk organic matter (OM) and

  6. Sources of Variability in the Stable Carbon Isotopic Signatures of Fungal Methyl Chloride

    Science.gov (United States)

    Shaw, S. L.; Henn, M. R.; Chapela, I. H.; Conrad, M. S.; Goldstein, A. H.

    2004-12-01

    The atmospheric budgets of the stratospheric ozone-depleting methyl halides are currently poorly constrained by known sources and sinks. Use of an isotopic mass balance technique may clarify these budgets by constraining the magnitudes of unknown or previously estimated fluxes, or by suggesting potential additional sources or sinks. The utility of this approach will depend not only on being able to measure the relevant source signatures and loss kinetic isotope effects contributing to their atmospheric budgets, but also on our ability to assess the variability in these terms. We investigated sources of variability in the isotopic signatures associated with one component of the methyl chloride budget: production by wood-rot fungi. Using controlled laboratory cultures, measurements of the stable carbon isotopic signatures of growth medium, biomass, respired CO2, CH3Cl, and the carbon mass balance were made over the growth cycle of Inonotus andersonii. Fractionations between medium and biomass (1 permil), as well as biomass and gases (5 permil), were nearly constant during exponential and stationary phase growth. However, the signatures varied across fungal species and type of substrate. A survey of several Phellinus and Inonotus strains grown on C3 plant-derived medium resulted in CH3Cl with delta13C values ranging from -48.2 to -26.4 permil. Other species, including freshly isolated P. robustus and I. andersonii monocultures produced CH3Cl, but in insufficient quantities to determine the isotopic signature. Similarly, field samples of live and blue oak woods rotting through action of these two species did produce CH3Cl when augmented with 10 mM KCl/water solution, but in insufficient quantities to determine isotopic signature. Growth of I. andersonii on C4 plant-derived medium resulted in a larger depletion in the delta13C value of CH3Cl as compared to substrate (18 permil) than for C3 plant-derived medium (7 permil). The amount of available oxygen also plays a role

  7. Use of carbon isotopes to identify and characterize microbial signatures in hydrothermal settings

    Science.gov (United States)

    Pancost, R. D.; Pressley, S.; Coleman, J.; Liane, B. G.; Mountain, B. W.

    2004-12-01

    To further explore the diversity of the microorganisms, their adaptations to extreme environmental conditions and their relationship with geothermal sinter formation, we examined the lipids preserved in six sinters of the Taupo Volcanic Zone (TVZ), New Zealand. These sinters contain microbial remains, but the process of mineralisation has rendered them largely unidentifiable. In contrast, lipids, including free fatty acids, 1,2-diacylglycerophospholipids, 1,2-di-O-alkylglycerols, glycerol dialkyl glycerol tetraethers and 1-O-alkylglycerols, are abundant and can be used as chemotaxonomic indicators. However, interpretation of lipid data and microbial signatures can be complicated by 1) allochthonous (pollen, leaves, fungal spores) inputs; 2) the presence of novel lipids or unknown origin; and 3) the production of the same compounds by a range of microorganisms. This is particularly true in hydrothermal settings, where microorganisms will biosynthesize compounds not commonly attributed to Bacteria or Archaea. Compound-specific carbon isotope analyses can help decipher the lipid signature by distinguishing different organic matter sources. For example, in all TVZ sinters, fatty acids with carbon numbers ranging from C22 to C32 are present; typically these are attributed to higher plants but they could also represent microbial adaptations to high temperatures. Consistent with the former interpretation, in three of four sinters, high-molecular-weight fatty acid carbon isotopic compositions range from -29 to -32 per mil. However, in a fourth sinter, in which fatty acids are most abundant, their carbon isotopic compositions range from -27 to -41 per mil in a pattern indicative of mixing of two different sources, one of which is almost certainly microbial. Carbon isotopic analyses also shed new light on the sources of novel compounds. Present at one hydrothermal site is a novel series of macrocyclic diethers, analogous to macrocyclic archaeol found in M. jannaschii but

  8. Using Oxygen and Carbon Isotopic Signatures in Order to Infer Climatic and Dietary Information in Roman Edessa, Greece

    Science.gov (United States)

    Michael, Dimitra-Ermioni; Dotsika, Elissavet

    2017-12-01

    Even though many isotopic studies have been conducted on ancient populations from Greece for the purpose of dietary reconstruction; mostly through carbon and nitrogen isotopic signals of bone collagen, less attention has been given to the utility of apatite signatures (oxygen and carbon) as dietary and palaeoenvironmental tools. Moreover, until recently the isotopic signal of tooth enamel for both the purposes of environmental and dietary reconstructions has been rarely assessed in ancient Greek societies. Therefore, the present study aims to provide with novel isotopic information regarding Edessa; a town in Northern Greece, during the Roman period. The current study primarily aims to explore the possible differentiation between the present climatic conditions in Edessa in relation to those occurring at the Roman period. Secondly, this study aims to reveal the significant utility of enamel isotopic signatures (carbon and oxygen) in palaeoenvironmental and palaeodietary studies regarding ancient human remains. The isotopic analyses have been conducted at the Stable Isotope and Radiocarbon Unit of INN, NCSR “Demokritos”. The population of Roman Edessa (2nd-4th c. AD) consists of 22 individuals, providing with 19 bone samples and 16 enamel ones. The mean enamel oxygen value is at -7.7 ±1.1 %0, the bone apatite mean oxygen value at -9.2 ±1.9 %0, and finally the mean carbon enamel value is at -11.7 ±1.2 %0. Oxygen values probably indicate that Edessa had a cooler climate during the Roman times in relation to present conditions, even though more research should be carried out in order to be more certain. In addition, the possible existence of non-local individuals has been revealed through the oxygen teeth enamel-bone apatite spacing. Finally, the carbon enamel signature has pointed out possible differentiations between the adult and the juvenile diet. Based on Edessa’s findings, the stated study strongly encourages the enamel oxygen and carbon isotopic signals

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

    Science.gov (United States)

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

    2010-01-01

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

  10. Insect outbreaks produce distinctive carbon isotope signatures in defensive resins and fossiliferous ambers

    Science.gov (United States)

    McKellar, Ryan C.; Wolfe, Alexander P.; Muehlenbachs, Karlis; Tappert, Ralf; Engel, Michael S.; Cheng, Tao; Sánchez-Azofeifa, G. Arturo

    2011-01-01

    Despite centuries of research addressing amber and its various inclusions, relatively little is known about the specific events having stimulated the production of geologically relevant volumes of plant resin, ultimately yielding amber deposits. Although numerous hypotheses have invoked the role of insects, to date these have proven difficult to test. Here, we use the current mountain pine beetle outbreak in western Canada as an analogy for the effects of infestation on the stable isotopic composition of carbon in resins. We show that infestation results in a rapid (approx. 1 year) 13C enrichment of fresh lodgepole pine resins, in a pattern directly comparable with that observed in resins collected from uninfested trees subjected to water stress. Furthermore, resin isotopic values are shown to track both the progression of infestation and instances of recovery. These findings can be extended to fossil resins, including Miocene amber from the Dominican Republic and Late Cretaceous New Jersey amber, revealing similar carbon-isotopic patterns between visually clean ambers and those associated with the attack of wood-boring insects. Plant exudate δ13C values constitute a sensitive monitor of ecological stress in both modern and ancient forest ecosystems, and provide considerable insight concerning the genesis of amber in the geological record. PMID:21429925

  11. Insect outbreaks produce distinctive carbon isotope signatures in defensive resins and fossiliferous ambers.

    Science.gov (United States)

    McKellar, Ryan C; Wolfe, Alexander P; Muehlenbachs, Karlis; Tappert, Ralf; Engel, Michael S; Cheng, Tao; Sánchez-Azofeifa, G Arturo

    2011-11-07

    Despite centuries of research addressing amber and its various inclusions, relatively little is known about the specific events having stimulated the production of geologically relevant volumes of plant resin, ultimately yielding amber deposits. Although numerous hypotheses have invoked the role of insects, to date these have proven difficult to test. Here, we use the current mountain pine beetle outbreak in western Canada as an analogy for the effects of infestation on the stable isotopic composition of carbon in resins. We show that infestation results in a rapid (approx. 1 year) (13)C enrichment of fresh lodgepole pine resins, in a pattern directly comparable with that observed in resins collected from uninfested trees subjected to water stress. Furthermore, resin isotopic values are shown to track both the progression of infestation and instances of recovery. These findings can be extended to fossil resins, including Miocene amber from the Dominican Republic and Late Cretaceous New Jersey amber, revealing similar carbon-isotopic patterns between visually clean ambers and those associated with the attack of wood-boring insects. Plant exudate δ(13)C values constitute a sensitive monitor of ecological stress in both modern and ancient forest ecosystems, and provide considerable insight concerning the genesis of amber in the geological record.

  12. Stable carbon isotopic signature of methane from high-emitting wetland sites in discontinuous permafrost landscape

    Science.gov (United States)

    Marushchak, Maija; Liimatainen, Maarit; Lind, Saara; Biasi, Christina; Martikainen, Pertti

    2017-04-01

    The rising methane concentration in the atmosphere during the past years has been associated with a concurrent change in the carbon isotopic signature: The atmospheric methane is getting more and more depleted in the heavy carbon isotope. The decreasing 13C/12C ratio indicates an increasing contribution of methane from biogenic sources, most importantly wetlands and inland waters, whose global emissions are still poorly constrained. From the climate change perspective, arctic and subarctic wetlands are particularly interesting due to the strong warming and permafrost thaw predicted for these regions that will cause changes in the methane dynamics. Coupling methane flux inventories with determination of the stable isotopic signature can provide useful information about the pathways of methane production, consumption and transport in these ecosystems. Here, we present data on the emissions and carbon isotopic composition of methane from subarctic tundra wetlands at the Seida study site, Northeast European Russia. In this landscape, underlain by discontinuous permafrost, waterlogged fens represent sites of high carbon turnover and high methane release. Despite they cover less than 15% of the region, their methane emissions comprise 98% of the regional mean (± SD) release of 6.7 (± 1.8) g CH4 m-2 y-1 (Marushchak et al. 2016). The methane emission from the studied fens was clearly depleted in 13C compared to the pore water methane. The bulk mean δ13CH4 (± SD) over the growing season was -68.2 (± 2.0) ‰ which is similar to the relatively few values previously reported from tundra wetlands. We explain the depleted methane emissions by the high importance of passive transport via aerenchymous plants, a process that discriminates against the heavier isotopes. This idea is supported by the strong positive correlation observed between the methane emission and the vascular leaf area index (LAI), and the inverse relationship between the δ13CH4 of emitted methane and LAI

  13. The carbon and oxygen isotope records of reef-dwelling foraminifers subjected to five varied pCO2 seawater

    Science.gov (United States)

    Hikami, M.; Ishimura, T.; Suzuki, A.; Nojiri, Y.; Kawahata, H.

    2013-12-01

    Ocean acidification (OA) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Reef dwelling foraminifera is one of the most important primary and carbonate producers in coral reef environments. Their shells are composed of high-Mg calcite and they are host to algal endosymbionts. In our previous culture experiment with two algal reef dwelling foraminifers, Amphisorus kudakajimensis and Calcarina gaudichaudii in the seawater of five different pCO2 conditions, net calcification of A. kudakajimensis was reduced under higher pCO2, whereas net calcification of C. gaudichaudii showed continued increasing trend with pCO2. These contrasting responses between the two species are possibly due to differences in calcification mechanisms and to links between calcification by the foraminifers and photosynthesis by the algal endosymbionts. But the factors affecting these calcification mechanisms are poorly understood. In this study, to get a better understanding of the effect of OA on their calcification, we cultured three reef dwelling foraminifers: Amphisorus hemprichii, belong to imperforate species, Baculogypsina sphaerulata, and C. gaudichaudii belong to perforate species, in the seawater of five different pCO2 conditions and we address the response of carbon and oxygen isotopes of the carbonate shells of foraminifers. The oxygen isotope ratio of cultured foraminiferal tests under five varied pCO2 seawater indicated no significant correlation to pCO2 values. On the other hand, the carbon isotope ratio of foraminiferal tests indicated heavy trend with rising pCO2 in all species. Alteration of carbonate chemistry result from ocean acidification may be effect strongly on carbon isotope composition relate to metabolic system (i.e. photosynthesis and respiration). In perforate species, both of oxygen and carbon isotope ratio were lighter than that

  14. Hydrogen isotopic compositions of organic compounds in plants reflect the plant's carbon metabolism

    Science.gov (United States)

    Cormier, M. A.; Kahmen, A.; Werner, R. A.

    2015-12-01

    The main factors controlling δ2H of plant organic compounds are generally assumed to be the plant's source water and the evaporative deuterium enrichment of leaf water. Hydrogen isotope analyses of plant compounds from sediments or tree rings are therefore mainly applied to assess hydrological conditions at different spatial and temporal scales. However, the biochemical hydrogen isotope fractionation occurring during biosynthesis of plant organic compounds (ɛbio) also accounts for a large part of the variability observed in the δ2H values. Nevertheless, only few studies have directly addressed the physiological basis of this variability and even fewer studies have thus explored possible applications of hydrogen isotope variability in plant organic compounds for plant physiological research. Here we show two datasets indicating that the plant's carbon metabolism can have a substantial influence on δ2H values of n-alkanes and cellulose. First, we performed a controlled experiment where we forced plants into heterotrophic and autotrophic C-metabolism by growing them under four different light treatments. Second, we assessed the δ2H values of different parasitic heterotrophic plants and their autotrophic host plants. Our two datasets show a systematic shift in ɛbio of up to 80 ‰ depending on the plant's carbon metabolism (heterotrophic or autotrophic). Differences in n-alkane and cellulose δ2H values in plants with autotrophic vs. heterotrophic metabolisms can be explained by different NADPH pools that are used by the plants to build their compounds either with assimilates that originate directly from photosynthesis or from stored carbohydrates. Our results have significant implications for the calibration and interpretation of geological records. More importantly, as the δ2H values reflect the plant's carbon metabolism involved during the tissue formation, our findings highlight the potential of δ2H values as new tool for studying plant and ecosystem carbon

  15. Dynamics of carbon in deep soils inferred from carbon stable isotopes signatures : a worldwide meta-analysis

    Science.gov (United States)

    Balesdent, Jérôme; Basile-Doelsch, Isabelle; Chadoeuf, Joël; Cornu, Sophie; Derrien, Delphine; Fekiacova, Zuzana; Hatté, Christine

    2014-05-01

    The contribution of soil carbon deeper than 30 cm to the atmospheric carbon balance is still poorly understood. A very straightforward quantification of the gross exchange of carbon between the atmosphere and soil organic matter can be obtained at places where the 13C/12C signature of vegetation has been changed for known durations, due to switch of the photosynthetic metabolism (C3 or C4) or to Free Air Carbon Enrichment experiments. We compiled C and 13C profile data of 113 sites of this type, either gahered from the literature or from our own measurements. Each site comprised two profiles : one where the 13C/12C of the vegetation had been changed, and a reference profile with unchanged vegetation 13C/12C. An isotope mixing equation was used, which takes into account the natural isotope enrichments with depth and decay. Three main variables were calculated at any depth from 0 to 100 cm and in a few sites down to 200 cm : the carbon content, the proportion of new carbon (aged less than the duration of change t) and the amount of new carbon. The database concerned 23 countries, various climates (58% intertropical and 42% between 23° to 56° latitude) and various soil types and textures. Landuses and vegetation consisted in 26% of forests and woodlands, 35% of grasslands and 38% of cropped systems. The duration of the natural labelling t ranged from 2 years to ca. 4000 years. Peatlands, boreal, and desert environments were absent from the database. Non-linear regressions with time across the dataset yielded kinetic parameters of the age distribution on one hand and of the flux of new carbon incorporation (kg C m-2 yr-1) on the other, each calculated by 10 cm depth increments. On the average, the median ages of carbon increase from ca. 15 years at 0 cm to more than 1000 years at 100 cm. Turnover is on the average 2 to 3 times slower for the subsoil (30-100 cm) than for the topsoil (0-30 cm). Based on the incorporation of new C in the first decades, the carbon input

  16. CO{sub 2}-recycling by plants: how reliable is the carbon isotope estimation?

    Energy Technology Data Exchange (ETDEWEB)

    Siegwolf, R.T.W.; Saurer, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Koerner, C. [Basel Univ., Basel (Switzerland)

    1997-06-01

    In the study of plant carbon relations, the amount of the respiratory losses from the soil was estimated, determining the gradient of the stable isotope {sup 13}C with increasing plant canopy height. According to the literature 8-26% of the CO{sub 2} released in the forests by soil and plant respiratory processes are reassimilated (recycled) by photosynthesis during the day. Our own measurements however, which we conducted in grass land showed diverging results from no indicating of carbon recycling, to a considerable {delta}{sup 13}C gradient suggesting a high carbon recycling rate. The role of other factors, such as air humidity and irradiation which influence the {delta}{sup 13}C in a canopy as well, are discussed. (author) 3 figs., 4 refs.

  17. Eocene-Miocene carbon-isotope and floral record from brown coal seams in the Gippsland Basin of southeast Australia

    Science.gov (United States)

    Holdgate, Guy R.; McGowran, Brian; Fromhold, Tom; Wagstaff, Barbara E.; Gallagher, Stephen J.; Wallace, Malcolm W.; Sluiter, Ian R. K.; Whitelaw, Michael

    2009-01-01

    The carbon-isotope and palynological record through 580 m thick almost continuous brown coal in southeast Australia's Gippsland Basin is a relatively comprehensive southern hemisphere Middle Eocene to Middle Miocene record for terrestrial change. The carbon isotope δ 13C coal values of these coals range from - 27.7‰ to - 23.2. This isotopic variability follows gymnosperm/angiosperm fluctuations, where higher ratios coincide with heavier δ13C values. There is also long-term variability in carbon isotopes through time. From the Eocene greenhouse world of high gymnosperm-heavier δ13C coal values, there is a progressive shift to lighter δ13C coal values that follows the earliest (Oi1?) glacial events around 33 Ma (Early Oligocene). The overlying Oligocene-Early Miocene brown coals have lower gymnosperm abundance, associated with increased % Nothofagus (angiosperm), and lightening of isotopes during Oligocene cooler conditions. The Miocene palynological and carbon-isotope record supports a continuation to the Oligocene trends until around the late Early Miocene (circa 19 Ma) when a warming commenced, followed by an even stronger isotope shift around 16 Ma that peaked in the Middle Miocene when higher gymnosperm abundance and heavier isotopes prevailed. The cycle between the two major warm peaks of Middle Eocene and Middle Miocene was circa 30 Ma long. This change corresponds to a fall in inferred pCO 2 levels for the same period. The Gippsland data suggest a link between gymnosperm abundance, long-term plant δ13C composition, climatic change, and atmospheric pCO 2. Climatic deterioration in the Late Miocene terminated peat accumulation in the Gippsland Basin and no further significant coals formed in southeast Australia. The poor correspondence between this terrestrial isotope data and the marine isotope record is explained by the dominant control on δ13C by the gymnosperm/angiosperm abundance, although in turn this poor correspondence may reflect palaeoclimate

  18. Early History of Acapulco and Lodran Constrained by the Nanostructure and C, N Isotopic Composition of Their Carbons

    Science.gov (United States)

    Charon, E.; Aléon, J.; Rouzaud, J. N.

    2012-03-01

    New results of structure and C, N isotopes of carbons on A-L meteorites allows us to defend an original history of A-L parent body benefiting of previous interpretations implying shock after the peak temperature and seeding by an exogenous carbons.

  19. Biomarker and carbon isotopic constraints on bacterial and algal community structure and functioning in a turbid, tidal estuary

    NARCIS (Netherlands)

    Boschker, H.T.S.; Kromkamp, J.C.; Middelburg, J.J.

    2005-01-01

    We studied planktonic community structure and isotopic composition using compound-specific 13C analysis of phospholipid-derived fatty acids (PLFA) along the Scheldt estuary during a spring bloom. A comprehensive set of other carbon cycle parameters was also determined. Based on dissolved carbon

  20. Inorganic origin of carbon dioxide during low temperature thermal recovery of bitumen: Chemical and isotopic evidence

    Science.gov (United States)

    Hutcheon, Ian; Abercrombie, Hugh J.; Krouse, H. R.

    1990-01-01

    Carbon dioxide, produced at low temperatures, is the dominant gaseous species evolved during steam-assisted thermal recovery of bitumen at the Tucker Lake pilot, Cold Lake, Alberta. Two possible sources for the produced CO 2 are considered: pyrolysis of bitumen and dissolution of carbonate minerals. Data from natural systems and experiments by other authors suggest that clay-carbonate reactions are the dominant source of CO 2. Carbon isotope and chemical analyses of produced gas and water reveal that CO 2 and HCO 3- become more enriched in 13C, and concentrations of Ca 2+ and HCO 3- rise during production. Temperatures in the producing zone are estimated to be between 70 and 220°C using the Na/K and chalcedony chemical geothermometers, and show that production of 13C-enriched CO 2 and HCO 3- occurs as temperature decreases during production. This extends the temperature range at which CO 2 is known to be produced from carbonates to lower levels than previously noted. The δ 13C of calcite in the reservoir is enriched in δ 13C, giving values as high as + 17.4%. When the calcite isotopic compositions are combined with temperature data and temperature fractionation equations for calcite, CO 2, and HCO 3-, they show calcite to be the only viable source of CO 2. Bitumen pyrolysis may contribute small amounts of CO 2, probably by decarboxylation, early in the production cycle but cannot contribute significant volumes. The recognition of production of CO 2 by reactive calcite destruction at temperatures between 70 and 220°C suggests that this process may be responsible for the production of large quantities of CO 2 in natural systems, particularly in lithofeldspathic sands and shales with high carbonate content and abundant clays. Organic acids have been suggested to be the source of CO 2 in diagenetic fluids, but the results presented here suggest that this hypothesis requires more complete investigation.

  1. [Identification of using organic carbon isotopic composition of soil pollution process].

    Science.gov (United States)

    Guo, Qing-Jun; Chen, Tong-Bin; Yang, Jun; Strauss, Harald; Lei, Mei; Zhu, Guang-Xu; Li, Yan-Mei; Zhou, Xiao-Yong; Li, Xiao-Yan

    2011-10-01

    This study has taken advantage of the characteristics of concentration of soil organic matter (SOC) and delta13 C(SOC) values to provide proofs for environment quality assessment and to know more about polluted sources, sizes and processes in Beijing steel company area. delta13C values of SOC is good for tracing sources and documenting shifts in community composition and distribution. Two sections (Beijing steel company area and Yongledian, Tongzhou) which belong to two different soil types collected in Beijing, and organic carbon isotopic composition and total soil organic carbon were analyzed. These results shows that SOC of soil samples from Beijing steel company area are quite high, and even 9.7% at the surface sample, however SOC from unpolluted area (Yongledian area) is lower than those of industrial area. delta13 C(SOC) from soils of Beijing steel company area and Yongledian area respectively vary from -24.8 per thousand to -23.1 per thousand and -26.4 per thousand to -20.5 per thousand, the results are quite different. The results reflect that there are different organic carbon sources in different types' soil: Organic carbon from Beijing steel company area has been mainly affected by coal burning, soil organic carbon concentrations are quite high, and pollution can affect on soils 70 cm deep underground; and soils from Yongledian area, have been not polluted, and organic matter is from natural litter (C3 plants). Although there are different soil organic carbon concentrations and isotope compositions, two soil sections have similar variation trends. This study provides proofs for environment quality assessment and know more about polluted and natural sources, sizes in Beijing.

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    to differentiate these two groups of natural vanillin from vanillin produced otherwise. Vanilla flavors were also analyzed for ratios of hydrogen stable isotopes (delta H-2). A graphic representation of delta C-13 versus delta H-2 revealed that vanillin extracted from pods grown in adjacent geographic origins......Authenticity and traceability of vanilla flavors were investigated using gas chromatographyisotope ratio mass spectrometry (GC-IRMS). Vanilla flavors produced by chemical synthesis (n = 2), fermentation (n = 1), and extracted from two different species of the vanilla orchid (n = 79) were analyzed....... The authenticity of the flavor compound vanillin was evaluated on the basis of measurements of ratios of carbon stable isotopes (delta C-13). It was found that results of delta C-13 for vanillin extracted from Vanilla planifolia and Vanilla tahitensis were significantly different (t test) and that it was possible...

  3. Neutron-rich isotope production using a uranium carbide - carbon nanotubes SPES target prototype

    Science.gov (United States)

    Corradetti, S.; Biasetto, L.; Manzolaro, M.; Scarpa, D.; Carturan, S.; Andrighetto, A.; Prete, G.; Vasquez, J.; Zanonato, P.; Colombo, P.; Jost, C. U.; Stracener, D. W.

    2013-05-01

    The SPES (Selective Production of Exotic Species) project, under development at the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL), is a new-generation Isotope Separation On-Line (ISOL) facility for the production of radioactive ion beams by means of the proton-induced fission of uranium. In the framework of the research on the SPES target, seven uranium carbide discs, obtained by reacting uranium oxide with graphite and carbon nanotubes, were irradiated with protons at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL). In the following, the yields of several fission products obtained during the experiment are presented and discussed. The experimental results are then compared to those obtained using a standard uranium carbide target. The reported data highlights the capability of the new type of SPES target to produce and release isotopes of interest for the nuclear physics community.

  4. The thermal dependence of carbon stable isotope incorporation and trophic discrimination in the domestic cricket, Acheta domesticus.

    Science.gov (United States)

    Cloyed, Carl S; Eason, Perri K; Dell, Anthony I

    2018-02-09

    Stable isotopes are valuable tools in physiological and ecological research, as they can be used to estimate diet, habitat use, and resource allocation. However, in most cases a priori knowledge of two key properties of stable isotopes is required, namely their rate of incorporation into the body (incorporation rate) and the change of isotope values between consumers and resources that arises during incorporation of the isotopes into the consumer's tissues (trophic discrimination). Previous studies have quantified these properties across species and tissue types, but little is known about how they vary with temperature, a key driver of many biological rates and times. Here, we explored for the first time how temperature affects both carbon incorporation rate and trophic discrimination via growth rates, using the domestic cricket, Acheta domesticus. We raised crickets at 16 °C, 21 °C, and 26 °C and showed that temperature increased carbon isotope incorporation rate, which was driven by both an increased growth rate and catabolism at higher temperatures. Trophic discrimination of carbon isotopes decreased at higher temperatures, which we attributed to either lower activation energies needed to synthesize non-essential amino acids at higher temperatures or the increased utilization of available resources of consumers at higher temperatures. Our results demonstrate that temperature is a key driver of both carbon isotope incorporation rate and trophic discrimination, via mechanisms that likely persist across all ectotherms. Experiments to determine incorporation rates and trophic discrimination factors in ectotherms must include temperature as a major factor, and natural variation in temperature might have significant effects on these isotopic properties that then can affect inferences made from isotope values. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-05-01

    In order to investigate the carbon episodes at Gosan background super-site (33.17° N, 126.10° E) in East Asia during spring of 2007 and 2008, total suspended particles (TSP) were collected and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The carbon episodes at the Gosan site were categorized as long-range transported anthropogenic pollutant (LTP) from Asian continent, Asian dust (AD) accompanying with LTP, and local pollen episodes. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during the pollen episodes (range: -26.2 ‰ to -23.5 ‰, avg.: -25.2 ± 0.9 ‰), followed by the LTP episodes (range: -23.5 ‰ to -23.0 ‰, avg.: -23.3 ± 0.3 ‰) and the AD episodes (range: -23.3 to -20.4 %, avg.: -21.8 ± 2.0 ‰). The δ13CTC of the airborne pollens (-28.0 ‰) collected at the Gosan site showed value similar to that of tangerine fruit (-28.1 ‰) produced from Jeju Island. Based on the carbon isotope mass balance equation and the TN and TC regression approach, we found that ∼40-45 % of TC in the TSP samples during the pollen episodes was attributed to airborne pollens from Japanese cedar trees planted around tangerine farms in Jeju Island. The δ13C of citric acid in the airborne pollens (-26.3 ‰) collected at the Gosan site was similar to that in tangerine fruit (-27.4 ‰). The negative correlation between the citric acid-carbon/TC ratios and δ13CTC were obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollens and then transported to the Gosan site. Based on the thermal evolution pattern of organic aerosols during the carbon episodes, we found that organic aerosols originated from East China are more volatile on heating and are more likely to form pyrolized organic carbon than the pollen-enriched organic aerosols and organic

  6. Late Miocene to Pliocene carbon isotope record of differential diet change among East African herbivores

    Science.gov (United States)

    Uno, Kevin T.; Cerling, Thure E.; Harris, John M.; Kunimatsu, Yutaka; Leakey, Meave G.; Nakatsukasa, Masato; Nakaya, Hideo

    2011-01-01

    Stable isotope and molecular data suggest that C4 grasses first appeared globally in the Oligocene. In East Africa, stable isotope data from pedogenic carbonate and fossil tooth enamel suggest a first appearance between 15–10 Ma and subsequent expansion during the Plio-Pleistocene. The fossil enamel record has the potential to provide detailed information about the rates of dietary adaptation to this new resource among different herbivore lineages. We present carbon isotope data from 452 fossil teeth that record differential rates of diet change from C3 to mixed C3/C4 or C4 diets among East African herbivore families at seven different time periods during the Late Miocene to the Pliocene (9.9–3.2 Ma). Significant amounts of C4 grasses were present in equid diets beginning at 9.9 Ma and in rhinocerotid diets by 9.6 Ma, although there is no isotopic evidence for expansive C4 grasslands in this part of the Late Miocene. Bovids and hippopotamids followed suit with individuals that had C4-dominated (>65%) diets by 7.4 Ma. Suids adopted C4-dominated diets between 6.5 and 4.2 Ma. Gomphotheriids and elephantids had mostly C3-dominated diets through 9.3 Ma, but became dedicated C4 grazers by 6.5 Ma. Deinotheriids and giraffids maintained a predominantly C3 diet throughout the record. The sequence of differential diet change among herbivore lineages provides ecological insight into a key period of hominid evolution and valuable information for future studies that focus on morphological changes associated with diet change. PMID:21464327

  7. Stable carbon and oxygen isotopes as an indicator for soil degradation

    Science.gov (United States)

    Alewell, C.; Schaub, M.; Seth, B.

    2009-04-01

    Analyses of soil organic carbon content (SOC) and stable carbon and oxygen isotope signatures (^13C) of soils were assessed for their suitability to detect early stage soil erosion. Results were validated with Cs-137 measurements. We investigated the soils in the alpine Urseren Valley (Southern Central Switzerland) which are highly impacted by soil erosion. Hill slope transects from uplands (cambisols) to adjacent wetlands (histosols and histic to mollic gleysols) differing in their intensity of visual soil erosion and reference wetlands without erosion influence were sampled. Carbon isotopic signature and SOC content of soil depth profiles were determined. A close correlation of ^13C and carbon content (r > 0.80) is found for upland soils not affected by soil erosion, indicating that depth profiles of ^13C of these upland soils mainly reflect decomposition of SOC. Long term disturbance of an upland soil is indicated by decreasing correlation of ^13C and SOC (r ? 0.80) which goes parallel to increasing (visual) damage at the site. Early stage soil erosion in hill slope transects from uplands to adjacent wetlands is documented as an intermediate ^13C value (27.5 ) for affected wetland soil horizons (0 - 12 cm) between upland (aerobic metabolism, relatively heavier ^13C of 26.6 ) and wetland isotopic signatures (anaerobic metabolism, relatively lighter ^13C of 28.6 ). Cs-137 measurements confirmed stable isotope analysis. Stable oxygen isotope signature (^18O) of soil is the result of a mixture of the components within the soil with varying ^18O signatures. Thus, ^18O of soils should provide information about the soil's substrate, especially about the relative contribution of organic matter versus minerals. As there is no standard method available for measuring soil ^18O, the method for measurement of single components using High Temperature Conversion Elemental Analyzer (TC/EA) was adapted. We measured ^18O in standard materials (IAEA 601, IAEA 602, Merck Cellulose

  8. The relationship between needle sugar carbon isotope ratios and tree rings of larch in Siberia.

    Science.gov (United States)

    Rinne, K T; Saurer, M; Kirdyanov, A V; Loader, N J; Bryukhanova, M V; Werner, R A; Siegwolf, R T W

    2015-11-01

    Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream metabolic processes and isotopic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ(13)C) of leaf assimilates and tree rings. For the first time, we compared the seasonal δ(13)C variability of leaf sucrose with intra-annual, high-resolution δ(13)C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends of the sucrose and tree ring δ(13)C records with little or no indication for the use of 'old' photosynthates formed during the previous year(s). The comparison of leaf sucrose δ(13)C values with that in other leaf sugars and in tree rings elucidates the cause for the reported (13)C-enrichment of sink organs compared with leaves. We observed that while the average δ(13)C of all needle sugars was 1.2‰ more negative than δ(13)C value of wood, the δ(13)C value of the transport sugar sucrose was on an average 1.0‰ more positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of sugars (leaf and phloem) with intra-annual tree ring δ(13)C measurements for deepening our understanding about the mechanisms controlling the isotope variability in tree rings under different environmental conditions. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Improved quantification of microbial CH4 oxidation efficiency in arctic wetland soils using carbon isotope fractionation

    Directory of Open Access Journals (Sweden)

    I. Preuss

    2013-04-01

    Full Text Available Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4. The observed accelerated warming of the arctic will cause deeper permafrost thawing, followed by increased carbon mineralization and CH4 formation in water-saturated tundra soils, thus creating a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4 signatures were measured and the fractionation factors for the processes of oxidation (αox and diffusion (αdiff were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (such as landfill cover soils have assumed a gas transport dominated by advection (αtrans = 1. In tundra soils, however, diffusion is the main gas transport mechanism and diffusive stable isotope fractionation should be considered alongside oxidative fractionation. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3. CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18. Furthermore, it was found that αox differs widely between sites and horizons (mean αox = 1.017 ± 0.009 and needs to be determined on a case by case basis. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by

  10. Zinc and sulfur isotope variation in sphalerite from carbonate-hosted zinc deposits, Cantabria, Spain

    Science.gov (United States)

    Pašava, Jan; Tornos, Fernando; Chrastný, Vladislav

    2014-10-01

    We studied zinc and sulfur isotopes and the chemical composition of sphalerite samples from Picos de Europa (Aliva mine) and sphalerite and hydrozincite samples from La Florida mine, two carbonate-hosted Mississippi Valley-type (MVT) deposits located in northern Spain; despite being close, they are hosted in carbonatic rocks of different ages, Lower Carboniferous and Lower Cretaceous, respectively. The two generations of sphalerite at Picos de Europa show different δ66Zn values (stage 1 sphalerite +0.24 per mil and stage 2 sphalerite from -0.75 to +0.08 per mil). Both generations also differ in the sulfur isotope composition (stage 1 has δ34S = +6.6 and stage 2 has δ34S = -0.9 to +2.9 per mil) and the chemical composition (stage 1 sphalerite, compared to stage 2 sphalerite, is significantly enriched in Pb, As, Mn, Sb, slightly enriched in Ag, Ni, and Cu and depleted in Co, Ga, Tl, Te, Ge, and Sn). We suggest that Zn isotope fractionation was controlled predominantly by pH and T changes. High Zn isotope values reflect rapid precipitation of sphalerite from higher-temperature acidic fluids that carried Zn mostly as chloride species after interaction with carbonate rocks while lower Zn isotope values most likely resulted from a longer precipitation process from fluid at higher pH and decreasing T that carried dominantly Zn sulfide species. At La Florida, sphalerite samples show light 66Zn-depleted signatures with δ66Zn values from -0.80 to -0.01 per mil (mostly between -0.80 and -0.24 per mil) and δ34S values from +10.7 to +15.7 per mil without any relationship between the δ66Zn and δ34S values. Here, the variation in Zn isotope values is interpreted as related to mixing of fluids from two reservoirs. The Zn was carried by a single deep-seated and higher T (~250-320 °C) fluid, and precipitation took place after mixing with a connate S-rich fluid in a system with mH2S > mZn2+ as a result of change in pH, T, and Zn predominant species. The light δ66Zn

  11. Integrating bio-, chemo- and sequence stratigraphy of the Late Ordovician, Early Katian: A connection between onshore and offshore facies using carbon isotope analysis: Kentucky, Ohio, USA

    Science.gov (United States)

    Young, Allison; Brett, Carlton; McLaughlin, Patrick

    2017-04-01

    , and mineralized surfaces. They also contain well studied fossil assemblages and event beds, which at the scale of an outcrop, allow for detailed paleoenvironmental interpretation. The offshore record of this interval, known almost exclusively from a few drill cores, displays an abrupt transition to distal, siliciclastic dominated facies, recording a more dysoxic and organic rich interval. Internal correlation of these shales has relied mostly on limited graptolite biostratigraphic and geochemical analysis. Here we seek to establish age relationships across a major facies transition between these two interrelated paleoenvironmental settings using high resolution whole rock carbon isotope analysis to integrate new and previous work on lithostratigraphy, biostratigraphy, and sequence stratigraphy of a series of cores and outcrops. Results to date demonstrate the persistence of carbon isotopic patterns (including the globally recognized GICE positive carbon isotopic excursion) permitting extension of correlation into basinal facies where tracking of stratigraphic sequences becomes difficult. A complicated relationship across the region is emerging involving both rapid facies transitions and submarine erosional cutout of units toward the center of the Sebree Trough. This study demonstrates the utility of an integrated stratigraphic approach for establishing high resolution regional correlations allowing for interpretations across a major facies transitions.

  12. Organic Geochemistry of the Hamersley Province: Relationships Among Organic Carbon Isotopes, Molecular Fossils, and Lithology

    Science.gov (United States)

    Eigenbrode, Jennifer L.

    2012-01-01

    Molecular fossils are particularly valuable ancient biosignatures that can provide key insight about microbial sources and ecology in early Earth studies. In particular, hopanes carrying 2-methyl or 3-methyl substituents are proposed to be derived from cyanobacteria and oxygen-respiring methanotrophs, respectively, based on both their modem occurrences and their Proterozoic and Phanerozoic sedimentary distributions. Steranes are likely from ancestral eukaryotes. The distribution of methylhopanes, steranes, and other biomarkers in 2.72-2.56 billion-year-old rocks from the Hamersley Province, Western Australia show relationships to lithology, facies, and isotopes of macromolecular carbon, and other biomarkers. These observations support biomarker syngenicity and thermal maturity. Moreover, ecological signatures are revealed, including a surprising relationship between isotopic values for bulk macromolecular carbon and the biomarker for methanotrophs. The record suggests that cyanobacteria were likely key organisms of shallow-water microbial ecosystems providing molecular oxygen, fixed carbon, and possibly fixed nitrogen, and methanotrophs were not alone in recycling methane and other C-13-depleted substrates.

  13. Deep-water carbonate dissolution in the northern South China Sea during Marine Isotope Stage 3

    Directory of Open Access Journals (Sweden)

    Na Wang

    2016-01-01

    Full Text Available The production, transportation, deposition, and dissolution of carbonate profoundly form part of the global carbon cycle and affect the amount and distribution of dissolved inorganic carbon (DIC and alkalinity (ALK, which drive atmospheric CO2 changes during glacial/interglacial cycles. These processes may provide significant clues for better understanding of the mechanisms that control the global climate system. In this study, we calculate and analyze the foraminiferal dissolution index (FDX and the fragmentation ratios of planktonic foraminifera for the 60–25 ka B.P. time-span, based on samples from Core 17924 and ODP Site 1144 in the northeastern South China Sea (SCS, so as to reconstruct the deep-water carbonate dissolution during Marine Isotope Stage 3 (MIS 3. Our analysis shows that the dissolution of carbonate increases gradually in Core 17924, whereas it remains stable at ODP Site 1144. This difference is caused by the deep-sea carbonate ion concentration ([CO32−] that affected the dissolution in Core 17924 where the depth of 3440 m is below the saturation horizon. However, the depth of ODP Site 1144 is 2037 m, which is above the lysocline where the water is always saturated with calcium carbonate; the dissolution is therefore less dependent of chemical changes of the seawater. The combined effect of the productivity and the deep-water chemical evolution may decrease deep-water [CO32−] and accelerate carbonate dissolution. The fall of the sea-level increased the input of DIC and ALK to the deep ocean and deepened the carbonate saturation depth, which caused an increase of the deep-water [CO32−]. The elevated [CO32−] partially neutralized the reduced [CO32−] contributed by remineralization of organic matter and slowdown of thermohaline. These consequently are the fundamental reasons for the difference in dissolution rate between these two sites.

  14. Factors controlling carbon isotopic composition of land snail shells estimated from lab culturing experiment

    Science.gov (United States)

    Zhang, Naizhong; Yamada, Keita; Yoshida, Naohiro

    2014-05-01

    Carbon isotopic composition (δ13C) of land snail shell carbonate is widely applied in reconstructing the C3/C4 vegetation distribution of paleo-environment, which is considered to reflect variations of some environmental parameters [1][2][3]. Land snail shell carbon has three potential sources: diet, atmospheric CO2 and ingested carbonate (limestone) [4]. However, their relative contributions to shell carbonate have not been understood well yet [4][5][6][7][8]. More researches are necessary before we could apply this tool in paleo-environment reconstruction, especially inter-lab culturing experiment. A kind of land snail species, Acusta despecta sieboldiana, was collected at Yokohama, Japan and cultured under suitable environment to lay eggs. The second generations were growing up from eggs to adults around 6-12 months at the temperature of 20°, 25° and 30°, respectively. All of the snails at 25° and 30° and most of those at 20° were fed by cabbage (C3 plant) during their life span while others were fed by corn (C4 plant). To investigate the effect of ingested carbonate, some of them were fed by Ca3(PO4)2 powder while others were fed by CaCO3 powder. δ13C of shells were analyzed by an Isotope Ratio Mass Spectrometry (Thermo Finnigan MAT 253); δ13C of food and snail tissue were measured by a Cavity Ring-Down Spectroscopy (Picarro G1121-i). At the same time, δ13C of eggshell and new born snails were analyzed by a Continuous Flow Isotope Ratio Mass Spectrometry (GasBench II). We confirmed that diet, atmospheric CO2 and ingested limestone could be important sources controlling shell δ13C values. And the temperature could affect shell carbonate δ13C values, too. A simple but credible frame was raised to discuss the mechanism of how each possible source and environmental parameter could affect shell carbonate δ13C values based on previous works [4][6][8] and this study. According to this frame and some reasonable assumptions, we have estimated the

  15. The fractionation factors of stable carbon and hydrogen isotope ratios for VOCs

    Science.gov (United States)

    Kawashima, H.

    2014-12-01

    Volatile organic compounds (VOCs) are important precursors of ozone and secondary organic aerosols in the atmosphere, some of which are carcinogenic, teratogenic, or mutagenic. VOCs in ambient air originate from many sources, including vehicle exhausts, gasoline evaporation, solvent use, natural gas emissions, and industrial processes, and undergo intricate chemical reactions in the atmosphere. To develop efficient air pollution remediation strategies, it is important to clearly identify the emission sources and elucidate the reaction mechanisms in the atmosphere. Recently, stable carbon isotope ratios (δ13C) of VOCs in some sources and ambient air have been measured by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). In this study, we measured δ13C and stable hydrogen isotope ratios (δD) of atmospheric VOCs by using the gas chromatography/thermal conversion/isotope ratio mass spectrometry coupled with a thermal desorption instrument (TD-GC/TC/IRMS). The wider δD differences between sources were found in comparison with the δ13C studies. Therefore, determining δD values of VOCs in ambient air is potentially useful in identifying VOC sources and their reactive behavior in the atmosphere. However, to elucidate the sources and behavior of atmospheric VOCs more accurately, isotopic fractionation during atmospheric reaction must be considered. In this study, we determined isotopic fractionation of the δ13C and δD values for the atmospheric some VOCs under irradiation conditions. As the results, δ13C for target all VOCs and δD for most VOCs were increasing after irradiation. But, the δD values for both benzene and toluene tended to decrease as irradiation time increased. We also estimated the fractionation factors for benzene and toluene, 1.27 and 1.05, respectively, which differed from values determined in previous studies. In summary, we were able to identify an inverse isotope effect for the δD values of benzene and toluene

  16. Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, Scott, F.; Levey, Douglas, J.; Greenberg, Catheryn, H.; Martinez del Rio, Carlos

    2003-02-28

    Pearson, S.F., D.J. Levey, C.H. Greenberg, and C.M. del Rio. 2003. Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird. Oecologia. 135:516-523. The use of stable isotopes to infer diet requires quantifying the relationship between diet and tissues and, in particular, knowing of how quickly isotopes turnover in different tissues and how isotopic concentrations of different food components change (discriminate) when incorporated into consumer tissues. We used feeding trials with wild-caught yellow-rumped warblers (Dendroica coronata) to determine d15N and d13C turnover rates for blood, d15N and d13C diet-tissue discrimination factors, and diet-tissue relationships for blood and feathers. After 3 weeks on a common diet, 36 warblers were assigned to one of four diets differing in the relative proportion of fruit and insects. Plasma half-life estimates ranged from 0.4 to 0.7 days for d13C and from 0.5 to 1.7 days for d15N. Half-life did not differ among diets. Whole blood half-life for d13C ranged from 3.9 to 6.1 days. Yellow-rumped warbler tissues were enriched relative to diet by 1.7.3.6% for nitrogen isotopes and by 1.2 to 4.3% for carbon isotopes, depending on tissue and diet. Consistent with previous studies, feathers were the most enriched and whole blood and plasma were the least enriched or, in the case of carbon, slightly depleted relative to diet. In general, tissues were more enriched relative to diet for birds with high percentages of insects. For all tissues, carbon and nitrogen isotope discrimination factors increased with carbon and nitrogen concentrations of diets. The isotopic signature of plasma increased linearly with the sum of the isotopic signature of the diet and the discrimination factor. Because the isotopic signature of tissues depends on both elemental concentration and isotopic signature of the diet, attempts to reconstruct diet from stable isotope signatures

  17. Covariant C and O Isotope Trends in Some Terrestrial Carbonates and ALH 84001: Possible Linkage Through Similar Formation Processes

    Science.gov (United States)

    Volk, Kathryn E.; Niles, Paul B.; Socki, Richard A.

    2011-01-01

    Carbonate minerals found on the surface of Mars and in martian meteorites indicate that liquid water has played a significant role in the planet's history. These findings have raised questions regarding the history of the martian hydrosphere and atmosphere as well as the possibility of life. Sunset Crater, Arizona is a dry environment with relatively high evaporation and brief periods of precipitation. This environment resembles Mars and may make Sunset Crater a good analog to martian carbonates. In this study we sought to identify discrete micro-scale isotopic variation within the carbonate crusts in Sunset Crater to see if they resembled the micro-scale isotope variation found in ALH 84001 carbonates. Sunset Crater carbonate formation may be used as a martian analog and ultimately provide insight into carbonate formation in ALH 84001.

  18. Using stable isotopes of nitrogen and carbon to study seabird ecology: applications in the Mediterranean seabird community

    Directory of Open Access Journals (Sweden)

    Manuela G. Forero

    2003-07-01

    Full Text Available The application of the stable isotope technique to ecological studies is becoming increasingly widespread. In the case of seabirds, stable isotopes of nitrogen and carbon have been mainly used as dietary tracers. This approach relieson the fact that food web isotopic signatures are reflected in the tissues of the consumer. In addition to the study of trophic ecology, stable isotopes have been used to track the movement of seabirds across isotopic gradients, as individuals moving between isotopically distinct foodwebs can carry with them information on the location of previous feeding areas. Studies applying the stable isotope methodology to the study of seabird ecology show a clear evolution from broad and descriptive approaches to detailed and individual-based analyses. The purpose of this article is to show the different fields of application of stable isotopes to the study of the seabird ecology. Finally, we illustrate the utility of this technique by considering the particularities of the Mediterranean seabird community, suggesting different ecological questions and conservation problems that could be addressed by using the stable isotope approach in this community.

  19. Tracing Organic Carbon from the Terrestrial to Marine Environment via Coupled Stable Carbon Isotope and Lignin Analyses

    Science.gov (United States)

    Childress, L. B.; Blair, N. E.; Leithold, E. L.

    2010-12-01

    The Waipaoa sedimentary system of New Zealand offers an opportunity to study the impacts of tectonic, climatic and anthropogenic forcings on the export of organic carbon from land and its preservation in the seabed. The dominant sources of organic carbon from the watershed are sedimentary rocks, aged soils, and flora. Marine C is added to sediment mid-shelf. Differential export and burial of the organic C from the different sources provides an organic geochemical record of changes in terrestrial and marine processes. Analyses of four marine sediment cores collected near the mouth of the Waipaoa River by the MATACORE in 2006 reveal both downcore (temporal) as well as across shelf (spatial) trends in carbon isotope and lignin parameters. These trends, coupled with measurements from soil profiles, rocks and riverine suspended sediments reveal changes in organic carbon sources that relate to terrestrial mass wasting processes and plant succession. As examples, approximately 4 kyr ago an event characterized by increased woody gymnosperm input was captured. This event may have been initiated by extensive landsliding of forested terrain. Upcore from that interval, a shift to non-woody angiosperms is documented. This succession coincides with a period of volcanic eruptions and later, human intrusion.

  20. In situ carbon isotope analysis of Archean organic matter with SIMS

    Science.gov (United States)

    Williford, K. H.; Ushikubo, T.; Lepot, K.; Hallmann, C.; Spicuzza, M. J.; Eigenbrode, J. L.; Summons, R. E.; Valley, J. W.

    2011-12-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to μm). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 μm using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 μm spot size with two Faraday cup detectors was 0.4%, and 0.8% for analyses using 1 μm and 3 μm spot sizes with a Faraday cup (for 12C) and an electron multiplier (for 13C). Eight coals, two ambers, a shungite, and a graphite were evaluated for μm-scale isotopic heterogeneity, and LCNN anthracite (δ13C = -23.56 ± 0.1%, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a 13CH/13C measurement included in every analysis and a 12CH measurement made immediately after every analysis. The total range of the H/C effect observed for the Archean samples analyzed was anthracite. Samples from the ABDP-9 (n=3; Mount McRae Shale, ~2.5 Ga), RHDH2a (n=2; Carrawine Dolomite and Jeerinah Fm, ~2.6 Ga), WRL1 (n=3; Wittenoom Fm, Marra Mamba Iron Formation, and Jeerinah Fm

  1. Spatially Resolved, In Situ Carbon Isotope Analysis of Archean Organic Matter

    Science.gov (United States)

    Williford, Kenneth H.; Ushikubo, Takayuki; Lepot, Kevin; Hallmann, Christian; Spicuzza, Michael J.; Eigenbrode, Jennifer L.; Summons, Roger E.; Valley, John W.

    2011-01-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to micron). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 micron using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 micron spot size with two Faraday cup detectors was 0.4 %, and 0.8 % for analyses using 1 micron and 3 micron spot sizes with a Faraday cup (for C-12) and an electron multiplier (for C-13). Eight coals, two ambers, a shungite, and a graphite were evaluated for micron-scale isotopic heterogeneity, and LCNN anthracite (delta C-13 = -23.56 +/- 0.1 %, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a C-13H/C-13 measurement included in every analysis. Matrix effects of variable C/SiO2 were evaluated by measuring mm to sub-micron graphite domains in quartzite from Bogala mine, Sri Lanka. Apparent instrumental bias and C-12 count rate are correlated in this case, but this may be related to a crystal orientation effect in graphite. Analyses of amorphous

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

    Science.gov (United States)

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

    2012-07-01

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

  3. Isotopic geochemistry of the Bamble granulite facies (Norway) and the origin of the deep crust carbonic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Pineau, F.; Javoy, M. (Paris-6 Univ., 75 (France)); Behar, F. (Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison); Touret, J. (Paris-6 Univ., 75 (France). Lab. de Spectroscopie des Plasmas)

    1981-01-01

    Various carbonaceous species found in granulite facies rocks from the Bamble area (Norway) have been separated and isotopically analyzed in order to specify mantle or crustal origin. Quartz crystals in the acidic rocks contain CO/sub 2/ fluid inclusions with isotopically light carbon, which can be related to mixtures of organic carbon common in the Scandinavian basement with minor amounts of CO/sub 2/ from decarbonatation of carbonates. These inclusions are supposed to represent the memory of prograde metamorphism. Acidic rocks as well as intrusive amphibolitized mafic rocks (hyperites) contain abundant late synmetamorphic carbonates, which, after their /sup 18/O composition, were precipitated or reequilibrated down to 400 deg C. Their delta/sup 13/C points to growing mantle influence just after the metamorphic paroxysm. The hyperites also contain large amounts of non carbonate carbon, released only upon fusion of the sample. This carbon is considered to represent carbon dissolved in the melt at the time of emplacement and trapped in the silicate network (interstitial defects or scapolite) during crystallization. Its concentration and isotopic composition is explained in terms of equilibrium with heavy carbonic fluid and partial outgassing under a few kbars.

  4. Carbon isotopes of Middle-Lower Jurassic coal-derived alkane gases from the major basins of northwestern China

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jinxing [PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083 (China); Department of Earth Science, Zhejiang University, Hangzhou 310027 (China); Faculty of Natural Resources and Information Technology, University of Petroleum, Beijing, 102200 (China); Zou, Caineng; Ni, Yunyan; Liu, Quanyou; Yang, Chun [PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083 (China); Li, Jian; Hu, Guoyi [PetroChina Research Institute of Petroleum Exploration and Development-Langfang Branch, Hebei 065007 (China); Zhang, Xiaobao [Lanzhou Institute of Geology, CAS, Lanzhou 730000 (China); Hu, Anping [Department of Earth Science, Zhejiang University, Hangzhou 310027 (China)

    2009-11-01

    Coal-derived hydrocarbons from Middle-Lower Jurassic coal-bearing strata in northwestern China are distributed in the Tarim, Junggar, Qaidam, and Turpan-Harmi basins. The former three basins are dominated by coal-derived gas fields, distributed in Cretaceous and Tertiary strata. Turpan-Harmi basin is characterized by coal-derived oil fields which occur in the coal measures. Based on analysis of gas components and carbon isotopic compositions from these basins, three conclusions are drawn in this contribution: 1) Alkane gases with reservoirs of coal measures have no carbon isotopic reversal, whereas alkane gases with reservoirs not of coal measures the extent of carbon isotopic reversal increases with increasing maturity; 2) Coal-derived alkane gases with high {delta}{sup 13}C values are found in the Tarim and Qaidam basins ({delta}{sup 13}C{sub 1}: - 19.0 to - 29.9 permille; {delta}{sup 13}C{sub 2}: - 18.8 to - 27.1 permille), and those with lowest {delta}{sup 13}C values occur in the Turpan-Harmi and Junggar basins ({delta}{sup 13}C{sub 1}: - 40.1 to - 44.0 permille; {delta}{sup 13}C{sub 2}: - 24.7 to - 27.9 permille); and 3) Individual specific carbon isotopic compositions of light hydrocarbons (C{sub 5-8}) in the coal-derived gases are lower than those in the oil-associated gases. The discovered carbon isotopic reversal of coal-derived gases is caused by isotopic fractionation during migration and secondary alteration. The high and low carbon isotopic values of coal-derived gases in China may have some significance on global natural gas research, especially the low carbon isotope value of methane may provide some information for early thermogenic gases. Coal-derived methane typically has much heavier {delta}{sup 13}C than that of oil-associated methane, and this can be used for gas-source rock correlation. The heavy carbon isotope of coal-derived ethane is a common phenomenon in China and it shed lights on the discrimination of gas origin. Since most giant gas

  5. Inorganic markers, carbonaceous components and stable carbon isotope from biomass burning aerosols in northeast China

    Science.gov (United States)

    Cao, F.; Zhang, Y.; Kawamura, K.

    2015-12-01

    To better characterize the sources of fine particulate matter (i.e. PM2.5) in Sanjiang Plain, Northeast China, aerosol chemical composition such total carbon (TC), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and inorganic ions were studied as well as stable carbon isotopic composition (δ13C) of TC. Intensively open biomass burning episodes were identified from late September to early October by satellite fire and aerosol optical depth maps. During the biomass burning episodes, concentrations of PM2.5, OC, EC, and WSOC increased by a factor of 4-12 compared to non-biomass-burning periods. Non-sea-salt potassium is strongly correlated with PM2.5, OC, EC and WSOC, suggesting an important contribution of biomass burning emission. The enrichment in both the non-sea-salt potassium and chlorine is significantly larger than other inorganic species, indicating that biomass burning aerosols in Sanjiang Plain is mostly fresh and less aged. In addition, WSOC to OC ratio is relatively lower compared to that reported in biomass burning aerosols in tropical regions, supporting that biomass burning aerosols in Sanjiang Plain is mostly primary and secondary organic aerosols is not significant. A lower average δ13C value (-26.2‰) is found for the biomass-burning aerosols, suggesting a dominant contribution from combustion of C3 plants in the studied region.

  6. Lead isotope ratios in a soil from a coal carbonization plant

    Energy Technology Data Exchange (ETDEWEB)

    Mercedes Diaz-Somoano; Montserrat Calvo; M. Antonia Lopez Anton; Isabel Suarez-Ruiz; Roberto Garcia; Sabino R. Moinelo; M. Rosa Martinez-Tarazon [Instituto Nacional del Carbon (CSIC), Oviedo (Spain)

    2007-05-15

    In the present work, lead isotope ratios were used to ascertain the enhancement of lead concentration in a soil derived from an experimental coking plant that processed 30 tons of coal per day over a period of 30 years. Isotope ratios were also used in this work to evaluate whether lead originated by this industrial activity may be leached and transported deep into the soil. It was found that variation in Pb concentrations in soil samples from the A Horizon, at various distances (7-35 m) from the coking battery, ranged between 17 and 349 {mu}g g{sup -1}, whereas in samples taken 50 m away, the concentration was less than 34 {mu}g g{sup -1}. This implies that all the operations involved in coal carbonization are responsible for the increase in the total amount of Pb in the thin top layer of the soil, although the concentration of lead was lower than the intervention limit values established for contaminated soils by Dutch Standards (530 {mu}g g{sup -1}). To establish the origin of pollution in this soil, lead isotope ratios of samples taken at different points were determined. The relationships between {sup 206}Pb/{sup 204}Pb and {sup 207}Pb/{sup 204}Pb indicated a mixture of natural and anthropogenic Pb. Although lead from industrial activity is present in the thin top layer, its presence decreased drastically between 0 and 30 cm depth. 18 refs., 5 figs., 3 tabs.

  7. Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland

    Science.gov (United States)

    Derry, Louis A.; Keto, Lisette S.; Jacobsen, Stein B.; Knoll, Andrew H.; Swett, Keene

    1989-01-01

    Precambrian Sr isotope stratigraphy was investigated by determining variations in Sr-87/Sr-86 ratios in the Upper Proterozoic carbonate succession from Svalbard and East Greenland. Data from this study were combined with those from literature to construct a curve of Sr-87/Sr-86 versus time for Upper Proterozoic seawater. The curve for the Upper Riphean-Vandian showed that the isotopic composition of Sr in seawater was low (Delta Sr-87 of about -500) between 900 and 650 Ma but rose rapidly to about +30 by 600 Ma (this range of long-term variation exceeds the total Phanerozoic variation). The very low values of Delta Sr-87 inferred for the Riphean require that, for this time, the submarine hydrothermal water flux was a large fraction of the Sr input to the oceans, while the rise in Delta Sr-87 in the Upper Proterozoic seawater reflects both a change in the ratio of hydrothermal and continental fluxes of Sr to the oceans, and a change in the isotopic composition of Sr from continental sources.

  8. Carbon isotope ratio (delta13C) values of urinary steroids for doping control in sport.

    Science.gov (United States)

    Cawley, Adam T; Trout, Graham J; Kazlauskas, Rymantas; Howe, Christopher J; George, Adrian V

    2009-03-01

    The detection of steroids originating from synthetic precursors in relation to their chemically identical natural analogues has proven to be a significant challenge for doping control laboratories accredited by the World Anti-Doping Agency (WADA). Endogenous steroid abuse may be confirmed by utilising the atomic specificity of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) that enables the precise measurement of differences in stable isotope ratios that arise as a result of fractionation patterns inherent in the source of steroids. A comprehensive carbon isotope ratio (delta(13)C) profiling study (n=1262) of urinary ketosteroids is reported that demonstrates the inter-individual variation that can be expected from factors such as diet, ethnicity, gender and age within and between different populations (13 countries). This delta(13)C distribution is shown by principal component analysis (PCA) to provide a statistical comparison to delta(13)C values observed following administration of testosterone enanthate. A limited collection of steroid diol data (n=100; consisting of three countries) is also presented with comparison to delta(13)C values of excreted testosterone to validate criteria for WADA accredited laboratories to prove doping offences.

  9. Carbon, Nitrogen, and Mercury Isotope Evidence for the Biogeochemical History of Mercury in Hawaiian Marine Bottomfish.

    Science.gov (United States)

    Sackett, Dana K; Drazen, Jeffrey C; Popp, Brian N; Choy, C Anela; Blum, Joel D; Johnson, Marcus W

    2017-11-22

    The complex biogeochemical cycle of Hg makes identifying primary sources of fish tissue Hg problematic. To identify sources and provide insight into this cycle, we combined carbon (δ13C), nitrogen amino acid (δ15NPhe), and Hg isotope (Δ199Hg, Δ201Hg, δ202Hg) data for six species of Hawaiian marine bottomfish. Results from these isotopic systems identified individuals within species that likely fed from separate food webs. Terrestrial freshwater inputs to coastal sediments were identified as the primary source of tissue Hg in the jack species, Caranx ignobilis, which inhabit shallow marine ecosystems. Thus, coastal C. ignobilis were a biological vector transporting Hg from freshwater environments into marine ecosystems. Depth profiles of Hg isotopic compositions for bottomfish (excludung C. ignobilis) were similar, but not identical, to profiles for open-ocean pelagic fishes, suggesting that in both settings inorganic Hg, which was ultimately transformed to monomethylmercury (MeHg) and bioaccumulated, was dominantly from a single source. However, differences between pelagic fish and bottomfish profiles were attributable to mass-dependent fractionation in the benthos prior to incorporation into the food web. Results also confirmed that bottomfish relied, at least in part, on a benthic food web and identified the incorporation of deeper water oceanic MeHg sources into deeper water sediments prior to food web uptake and transfer.

  10. Notes on the temperature dependence of carbon isotope fractionation by aerobic CH(4)-oxidising bacteria.

    Science.gov (United States)

    Nihous, Gerard C

    2010-06-01

    While the importance of environmental analyses based on isotope discrimination has been growing, uncertainties remain about underlying phenomena. Published results on the temperature dependence of carbon isotope fractionation during methane oxidation in various media show different trends. A decrease in fractionation is generally expected with temperature, but some data for methane oxidation in aqueous media show an inverse relationship. This apparent contradiction was probed by representing the first methane oxidation step as three elementary processes: the adsorption of methane on the bacterial cell wall, the desorption of methane from the wall, and the conversion of methane into methanol mediated by methane monooxygenase (MMO) enzymes. Assuming that the proportion of vacant adsorption sites is stationary, a formula for the composite fractionation factor alpha was obtained. It was shown that alpha not only expresses the fractionation that may occur in each elementary process, but that it also depends on the ratio of the kinetic rates for conversion into methanol and desorption. This result and experimental data were used to estimate the activation energy for the desorption of methane from methanotroph cell wall in aqueous medium ( approximately 200 kJ/mol). Simple Rosso models of bacterial maximal-specific growth rate were then used to demonstrate that alpha and the isotope fractionation from the MMO-mediated conversion into methanol alone could vary in opposite ways as temperature changes, but that care must be exercised when using fitted relationships across wide temperature ranges.

  11. Comparison of stable carbon isotope ratios in the whole wood, cellulose and lignin of Oak tree-rings

    CSIR Research Space (South Africa)

    Loader, NJ

    2003-08-01

    Full Text Available ; Libby et al., 1976; Farmer and Baxter, 1974), but since Wilson and Grinsted (1977) demonstrated that di?erent com- ponents of wood di?er isotopically, most studies have concentrated on analysis of cellulose, as the dominant and most easily isolated....V., 1990. Environmental infor- mation in the isotopic record in trees. Phil Trans. R. Soc. London A 330, 427^439. Farmer, J.G., Baxter, M.S., 1974. Atmospheric carbon dioxide levels as indicated by the stable isotope record in wood. Nature 247, 273...

  12. Chemical changes and carbon isotope variations in a cross-section of a large Miocene gymnospermous log

    Science.gov (United States)

    Bates, A.L.; Spiker, E. C.

    1992-01-01

    The cross-sectional radius of a 3-m (diam.) brown coal gymnospermous log of Miocene age, previously analyzed for carbohydrate and lignin methoxyl content by solid-state 13C nuclear magnetic resonance spectroscopy, was examined using stable carbon isotopic ratios in order to determine if the isotopic composition could be related to chemical changes or to radial position. This study found a possible relationship between ??13C-values and radial position; however, these changes cannot be linked to carbohydrate content and are probably attributable to changing growth conditions during the lifetime of the tree. An apparent linear relationship between the changes in carbohydrate content after sodium para-periodate treatment and corresponding changes in the ??13C-values indicates constant isotopic fractionation between lignin and carbohydrates along the cross-sectional radius. This result indicates that diagenesis has not produced any significant change in the lignin-carbohydrate carbon isotopic fractionation or, alternatively, that diagenesis has erased any fractionation pattern that once existed. A sample of fresh wood from another gymnospermous species was analyzed by the same methods and found to have lignin-carbohydrate carbon isotopic fractionation significantly different from that of the Miocene log section samples, suggesting that differences may be species-related or that the complex mixture of carbohydrates in the fresh wood was isotopically different from that of the degraded wood, and the whole Miocene log was uniformly altered. ?? 1992.

  13. Isotopic evidence of enhanced carbonate dissolution at a coal mine drainage site in Allegheny County, Pennsylvania, USA

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Shikha; Sack, Andrea; Adams, James P.; Vesper, Dorothy; J Capo, Rosemary C.; Hartsock, Angela; Edenborn, Harry M.

    2013-01-01

    Stable isotopes were used to determine the sources and fate of dissolved inorganic C (DIC) in the circumneutral pH drainage from an abandoned bituminous coal mine in western Pennsylvania. The C isotope signatures of DIC (δ{sup 13}C{sub DIC}) were intermediate between local carbonate and organic C sources, but were higher than those of contemporaneous Pennsylvanian age groundwaters in the region. This suggests a significant contribution of C enriched in {sup 13}C due to enhanced carbonate dissolution associated with the release of H{sub 2}SO{sub 4} from pyrite oxidation. The Sr isotopic signature of the drainage was similar to other regional mine waters associated with the same coal seam and reflected contributions from limestone dissolution and cation exchange with clay minerals. The relatively high δ{sup 34}S{sub SO4} and δ{sup 18}O{sub SO4} isotopic signatures of the mine drainage and the presence of presumptive SO{sub 4}-reducing bacteria suggest that SO{sub 4} reduction activity also contributes C depleted in {sup 13}C isotope to the total DIC pool. With distance downstream from the mine portal, C isotope signatures in the drainage increased, accompanied by decreased total DIC concentrations and increased pH. These data are consistent with H{sub 2}SO{sub 4} dissolution of carbonate rocks, enhanced by cation exchange, and C release to the atmosphere via CO{sub 2} outgassing.

  14. Isotopic investigations of contemporary carbonate sedimentation in lakes from N Poland

    Science.gov (United States)

    Piotrowska, Natalia; Gabryś, Alicja; Tylmann, Wojciech; Bonk, Alicja

    2015-04-01

    The study area of NE Poland is a region of most pron