How to Make Eccentricity Cycles in Stratigraphy: the Role of Compaction

Science.gov (United States)

Liu, W.; Hinnov, L.; Wu, H.; Pas, D.

2017-12-01

Milankovitch cycles from astronomically driven climate variations have been demonstrated as preserved in cyclostratigraphy throughout geologic time. These stratigraphic cycles have been identified in many types of proxies, e.g., gamma ray, magnetic susceptibility, oxygen isotopes, carbonate content, grayscale, etc. However, the commonly prominent spectral power of orbital eccentricity cycles in stratigraphy is paradoxical to insolation, which is dominated by precession index power. How is the spectral power transferred from precession to eccentricity in stratigraphy? Nonlinear sedimentation and bioturbation have long been identified as players in this transference. Here, we propose that in the absence of bioturbation differential compaction can generate the transference. Using insolation time series, we trace the steps by which insolation is transformed into stratigraphy, and how differential compaction of lithology acts to transfer spectral power from precession to eccentricity. Differential compaction is applied to unique values of insolation, which is assumed to control the type of deposited sediment. High compaction is applied to muds, and progressively lower compaction is applied to silts and sands, or carbonate. Linear differential compaction promotes eccentricity spectral power, but nonlinear differential compaction elevates eccentricity spectral power to dominance and precession spectral power to near collapse as is often observed in real stratigraphy. Keywords: differential compaction, cyclostratigraphy, insolation, eccentricity

High resolution carbon isotope stratigraphy and glendonite occurrences of the Christopher Formation, Sverdrup Basin (Axel Heiberg Island, Canada): implications for mid Cretaceous high latitude climate change

Science.gov (United States)

Herrle, Jens O.; Schröder-Adams, Claudia J.; Galloway, Jennifer M.; Pugh, Adam T.

2013-04-01

Understanding the evolution of Canada's Arctic region, as a crucial component of Earth's climate system, is fundamental to assess short and long-term climate, environmental, and paleogeographic change. However, the stratigraphy and paleoenvironmental evolution of the Cretaceous Arctic is poorly constrained and a detailed bio- and chemostratigraphic correlation of major mid-Cretaceous paleoceanographic turning points such as Oceanic Anoxic Events, cold snaps, and biotic turnovers with key locations of the high- and low latitudes is missing. Here we present for the first time a high resolution bio- and carbon isotope stratigraphy of the Arctic Albian Christopher Formation of the Sverdrup Basin at Glacier Fiord in the southern part of Axel Heiberg Island, Canadian High Arctic. By using these techniques we developed a high temporal framework to record major environmental changes as it is indicated by the occurrence of glendonites and sandstone intervals of our studied Albian succession. The Albian Christopher Formation is a shale dominated marine unit with a thickness of approximately 1200 m. Several transgressive/ regressive cycles can be recognized by prograding shoreface units that break up mudrock deposition. In addition, glendonites are mainly found in the lower part of the Christopher Formation. Glendonites are pseudomorphs of calcite, after the metastable mineral ikaite, and have been often described from high latitude Permian, Jurassic and Cretaceous marine environments from the Canadian Arctic, Spitsbergen and Australia. The formation of glendonites takes place in the uppermost layer of the sediment and requires near-freezing temperatures, high salinity, and orthophosphate-rich bottom water. Although the presence of glendonites implies a range of paleoenvironmental conditions there is a consensus in the scientific literature that they reflect cooler paleoenvironmental conditions. Preliminary bio- and carbon isotope stratigraphic results suggest that the

Application of sequence stratigraphy to carbonate reservoir prediction, Early Palaeozoic eastern Warburton basin, South Australia

Energy Technology Data Exchange (ETDEWEB)

Xiaowen S.; Stuart, W.J.

1996-12-31

The Early Palaeozoic Warburton Basin underlies the gas and oil producing Cooper and Eromanga Basins. Postdepositional tectonism created high potential fracture porosities, complicating the stratigraphy and making reservoir prediction difficult. Sequence stratigraphy integrating core, cuttings, well-log, seismic and biostratigraphic data has recognized a carbonate-dominated to mixed carbonate/siliciclastic supersequence comprising several depositional sequences. Biostratigraphy based on trilobites and conodonts ensures reliable well and seismic correlations across structurally complex areas. Lithofacies interpretation indicates sedimentary environments ranging from carbonate inner shelf, peritidal, shelf edge, deep outer shelf and slope to basin. Log facies show gradually upward shallowing trends or abrupt changes indicating possible sequence boundaries. With essential depositional models and sequence analysis from well data, seismic facies suggest general reflection configurations including parallel-continuous layered patterns indicating uniform neuritic shelf, and mounded structures suggesting carbonate build-ups and pre-existing volcanic relief. Seismic stratigraphy also reveals inclined slope and onlapping margins of a possibly isolated platform geometry. The potential reservoirs are dolomitized carbonates containing oomoldic, vuggy, intercrystalline and fracture porosities in lowstand systems tracts either on carbonate mounds and shelf crests or below shelf edge. The source rock is a deep basinal argillaceous mudstone, and the seal is fine-grained siltstone/shale of the transgressive system tract.

Application of sequence stratigraphy to carbonate reservoir prediction, Early Palaeozoic eastern Warburton basin, South Australia

Energy Technology Data Exchange (ETDEWEB)

Xiaowen S.; Stuart, W.J.

1996-01-01

The Early Palaeozoic Warburton Basin underlies the gas and oil producing Cooper and Eromanga Basins. Postdepositional tectonism created high potential fracture porosities, complicating the stratigraphy and making reservoir prediction difficult. Sequence stratigraphy integrating core, cuttings, well-log, seismic and biostratigraphic data has recognized a carbonate-dominated to mixed carbonate/siliciclastic supersequence comprising several depositional sequences. Biostratigraphy based on trilobites and conodonts ensures reliable well and seismic correlations across structurally complex areas. Lithofacies interpretation indicates sedimentary environments ranging from carbonate inner shelf, peritidal, shelf edge, deep outer shelf and slope to basin. Log facies show gradually upward shallowing trends or abrupt changes indicating possible sequence boundaries. With essential depositional models and sequence analysis from well data, seismic facies suggest general reflection configurations including parallel-continuous layered patterns indicating uniform neuritic shelf, and mounded structures suggesting carbonate build-ups and pre-existing volcanic relief. Seismic stratigraphy also reveals inclined slope and onlapping margins of a possibly isolated platform geometry. The potential reservoirs are dolomitized carbonates containing oomoldic, vuggy, intercrystalline and fracture porosities in lowstand systems tracts either on carbonate mounds and shelf crests or below shelf edge. The source rock is a deep basinal argillaceous mudstone, and the seal is fine-grained siltstone/shale of the transgressive system tract.

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

Czech Academy of Sciences Publication Activity Database

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

2014-01-01

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

High-resolution stratigraphy with strontium isotopes.

Science.gov (United States)

Depaolo, D J; Ingram, B L

1985-02-22

The isotopic ratio of strontium-87 to strontium-86 shows no detectable variation in present-day ocean water but changes slowly over millions of years. The strontium contained in carbonate shells of marine organisms records the ratio of strontium-87 to strontium-86 of the oceans at the time that the shells form. Sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium-87 to strontium-86 with a resolution that is similar to that of other techniques used in age correlation. This method may prove valuable for many geological, paleontological, paleooceanographic, and geochemical problems.

Morphology, stratigraphy and oxygen isotope composition of fossil glacier ice at Ledyanaya Gora, Northwest Siberia, Russia

International Nuclear Information System (INIS)

Vaikmaee, R.; Michel, F.A.; Solomatin, V.I.

1993-01-01

Studies of the stratigraphy, sedimentology, structure and isotope composition of a buried massive ice body and its encompassing sediments at Ledyanaya Gora in northwestern Siberia demonstrate that the ice is relict glacier ice, probably emplaced during the Early Weichselian. Characteristics of this ice body should serve as a guide for the identification of other relict buried glacier ice bodies in permafrost regions. 31 refs., 9 figs., 2 tabs

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

DEFF Research Database (Denmark)

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

2013-01-01

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

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 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 differences in both short

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.

Early-Middle Pleistocene benthic turnover and oxygen isotope stratigraphy from the Central Mediterranean (Valle di Manche, Crotone Basin, Italy): Data and trends

OpenAIRE

Michele Azzarone; Patrizia Ferretti; Veronica Rossi; Daniele Scarponi; Luca Capraro; Patrizia Macrì; John W. Huntley; Costanza Faranda

2018-01-01

Ostracod faunal turnover and oxygen isotope data (foraminifera) along the Valle di Manche (VdM) section are herein compiled. Specifically, the material reported in this work includes quantitative palaeoecological data and patterns of ostracod fauna framed within a high-resolution oxygen isotope stratigraphy (δ18O) from Uvigerina peregrina. In addition, the multivariate ostracod faunal stratigraphic trend (nMDS axis-1 sample score) is calibrated using bathymetric distributions of extant mollus...

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

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

Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

Science.gov (United States)

Kocsis, László; Ounis, Anouar; Chaabani, Fredj; Salah, Neili Mohamed

2013-06-01

Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions. 87Sr/86Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaoui s.s. Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene-Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII-V and layers IV-0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) re-working and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher 87Sr/86Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re-working due to low sea level. Conversely, the sample with lower 87Sr/86Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The ɛNd values of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These δ18O data reflect elevated ambient temperature, which may link to the Early Eocene

Biosynthetic effects on the stable carbon isotopic compositions of agal lipids: Implications for deciphering the carbon isotopic biomarker record

NARCIS (Netherlands)

Sinninghe Damsté, J.S.; Schouten, S.; Klein Breteler, W.C.M.; Blokker, P.; Schogt, N.; Rijpstra, W.I.C.; Grice, K.; Baas, M.

1998-01-01

Thirteen species of algae covering an extensive range of classes were cultured and stable carbon isotopic compositions of their lipids were analysed in order to assess carbon isotopic fractionation effects during their biosynthesis. The fatty acids were found to have similar stable carbon isotopic

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.

Carbon Isotope Chemostratigraphy, the Baby and the Bathwater

Science.gov (United States)

Arthur, M. A.

2008-12-01

Secular variations in the carbon isotopic values of carbonate sediments and rocks and their individual components have been applied successfully to problems of stratigraphic correlation and for interpretation of past changes in the global carbon cycle. However, this methodology is not without problems. A major tenet of stable isotope chemostratigraphy involves sampling and analyzing multiple, widely separated sequences, and, if possible, multiple carbon-bearing components (e.g., carbonate and organic carbon) in order to demonstrate a global signal. In some cases, this methodology has been short-circuited in the zeal to reveal a new event or excursion, particularly for time intervals for which adequate sequences are somewhat rare. Likewise, although most carbonate researchers are quite aware of the possible importance of diagenesis, particularly in organic-carbon rich sequences or in shoal-water carbonate sequences with longer-term subaerial exposure events, such overprints commonly go unrecognized or are considered of minor impact. Studies of stable isotope variations in carbonate sequences should always employ textural and geochemical methodologies for detecting and even quantifying diagenesis, if possible. Although some diagenetically overprinted or misinterpreted geochemical data have undoubtedly appeared in the literature, there are many excellent examples of global carbon isotope variations in records expressed in pelagic biogenic carbonate, marine organic carbon, platform carbonates, and terrestrial organic matter. Arguably, one of the best-documented examples is the Cenomanian-Turonian (ca. 93 Ma) positive carbon isotope excursion. The amplitude of the Cenomanian-Turonian carbon isotope excursion is similar among all types of records, but there are subtle pattern differences that arise from differences in sedimentation rate among and within sequences. Organic carbon and carbonate carbon isotope signals also may differ in phasing and amplitude for certain

Paleomagnetism and integrated stratigraphy of the Upper Berriasian hemipelagic succession in the Barlya section Western Balkan, Bulgaria: Implications for lithogenic input and paleoredox variations

Czech Academy of Sciences Publication Activity Database

Grabowski, J.; Lakova, I.; Petrova, S.; Stoykova, K.; Ivanova, D.; Wójcik-Tabol, P.; Sobien, K.; Schnabl, Petr

2016-01-01

Roč. 461, 1 November (2016), s. 156-177 ISSN 0031-0182 R&D Projects: GA ČR(CZ) GA16-09979S Institutional support: RVO:67985831 Keywords : biostratigraphy * carbon isotope stratigraphy * climate * magnetic susceptibility * magnetostratigraphy * sea-level changes Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.578, year: 2016

Brachiopod biogeochemistry and isotope stratigraphy from the Rhaetian Eiberg section in Austria

DEFF Research Database (Denmark)

Korte, Christoph; Thibault, Nicolas Rudolph; Ullmann, Clemens Vinzenz

2017-01-01

The end-Triassic is characterized by one of the most severe biotic crises of the entire Phanerozoic, with strong carbon cycle perturbations potentially predating the biotic event. In order to improve and test the chemostratigraphic framework for the Rhaetian Stage, which culminated in the end......-Triassic extinction, a total of 675 and 108 carbonate δ13C and δ18O values have been measured from bulk rock carbonate and articulate brachiopod samples from the Rhaetian Eiberg quarry succession (Northern Calcareous Alps, Austria) respectively. Both brachiopod and bulk rock oxygen isotope trends are compatible...... the calcite composing the bulk rock micrite. Significant metabolic disequilibrium effects on brachiopod carbon isotope ratios are suggested by a clear negative correlation between δ13C values and Sr/Ca ratios of the samples. Consequently, chemostratigraphy based on brachiopod Δ13C data, especially with regard...

Lithostratigraphy, petrography, biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifer system of western Collier County, Florida

Science.gov (United States)

Edwards, L.E.; Weedman, S.D.; Simmons, R.; Scott, T.M.; Brewster-Wingard, G. L.; Ishman, S.E.; Carlin, N.M.

1998-01-01

In 1996, seven cores were recovered in western Collier County, southwestern Florida, to acquire subsurface geologic and hydrologic data to support ground-water modeling efforts. This report presents the lithostratigraphy, X-ray diffraction analyses, petrography, biostratigraphy, and strontium-isotope stratigraphy of these cores. The oldest unit encountered in the study cores is an unnamed formation that is late Miocene. At least four depositional sequences are present within this formation. Calculated age of the formation, based on strontium-isotope stratigraphy, ranges from 9.5 to 5.7 Ma (million years ago). An unconformity within this formation that represents a hiatus of at least 2 million years is indicated in the Old Pump Road core. In two cores, Collier-Seminole and Old Pump Road, the uppermost sediments of the unnamed formation are not dated by strontium isotopes, and, based on the fossils present, these sediments could be as young as Pliocene. In another core (Fakahatchee Strand-Ranger Station), the upper part of the unnamed formation is dated by mollusks as Pliocene. The Tamiami Formation overlies the unnamed formation throughout the study area and is represented by the Ochopee Limestone Member. The unit is Pliocene and probably includes the interval of time near the early/late Pliocene boundary. Strontium-isotope analysis indicates an early Pliocene age (calculated ages range from 5.1 to 3.5 Ma), but the margin of error includes the latest Miocene and the late Pliocene. The dinocyst assemblages in the Ochopee typically are not age-diagnostic, but, near the base of the unit in the Collier-Seminole, Jones Grade, and Fakahatchee Strand State Forest cores, they indicate an age of late Miocene or Pliocene. The molluscan assemblages indicate a Pliocene age for the Ochopee, and a distinctive assemblage of Carditimera arata and Chione cortinaria in several of the cores specifically indicates an age near the early/late Pliocene boundary. Undifferentiated sands

Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

Science.gov (United States)

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

1986-01-01

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

Carbon isotope ratios of atmospheric carbon dioxide

International Nuclear Information System (INIS)

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

1982-01-01

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

Following Carbon Isotopes from Methane to Molecules

Science.gov (United States)

Freeman, K. H.

2017-12-01

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

Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

DEFF Research Database (Denmark)

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

2015-01-01

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

Carbon and Oxygen isotopic composition in paleoenvironmental determination

International Nuclear Information System (INIS)

Silva, J.R.M. da.

1978-01-01

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

Stable carbon isotope response to oceanic anoxic events

International Nuclear Information System (INIS)

Hu Xiumian; Wang Chengshan; Li Xianghui

2001-01-01

Based on discussion of isotope compositions and fractionation of marine carbonate and organic carbon, the author studies the relationship between oceanic anoxic events and changes in the carbon isotope fractionation of both carbonate and organic matter. During the oceanic anoxic events, a great number of organisms were rapidly buried, which caused a kind of anoxic conditions by their decomposition consuming dissolved oxygen. Since 12 C-rich organism preserved, atmosphere-ocean system will enrich relatively of 13 C. As a result, simultaneous marine carbonate will record the positive excursion of carbon isotope. There is a distinctive δ 13 C excursion during oceanic anoxic events in the world throughout the geological time. In the Cenomanian-Turonian anoxic event. this positive excursion arrived at ∼0.2% of marine carbonate and at ∼0.4% of organic matter, respectively. Variations in the carbon isotopic compositions of marine carbonate and organic carbon record the changes in the fraction of organic carbon buried throughout the geological time and may provide clues to the changes in rates of weathering and burial of organic carbon. This will provide a possibility of interpreting not only the changes in the global carbon cycle throughout the geological time, but also that in atmospheric p CO 2

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

The biostratigraphy of Sinemurian to lower Toarcian calcareous nannofossils has been investigated in the Sancerre-Couy core (Paris Basin), which contains a mixed assemblage of species with affinities to the northern and southern areas of the peri-tethyan realm, thus allowing for the use and calib......The biostratigraphy of Sinemurian to lower Toarcian calcareous nannofossils has been investigated in the Sancerre-Couy core (Paris Basin), which contains a mixed assemblage of species with affinities to the northern and southern areas of the peri-tethyan realm, thus allowing for the use...... 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...... between the different domains. In addition to the nine main bioevents used for the biozonation of the core, we document an additional 50 distinct bioevents, evaluate their reliability and discuss their potential significance by comparison to previous studies. A total of five significant negative organic...

Gluconeogenesis from labeled carbon: estimating isotope dilution

International Nuclear Information System (INIS)

Kelleher, J.K.

1986-01-01

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

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.

High-resolution carbonate isotopic study of the Mural Formation (Cerro Pimas section), Sonora, México: Implications for early Albian oceanic anoxic events

Science.gov (United States)

Madhavaraju, J.; Lee, Yong Il; Scott, R. W.; González-León, C. M.; Jenkyns, H. C.; Saucedo-Samaniego, J. C.; Ramasamy, S.

2018-03-01

The 420-m thick stratigraphic section of the Mural Formation that is exposed in the Cerro Pimas area of northern Sonora, Mexico, is composed of limestone lithofacies ranging from bioclastic wackestone to boundstone, whose biota is characterized by low diversity. Prominent age-diagnostic fossils are benthic foraminifera and long-ranging calcareous algae that indicate the Aptian/Albian boundary is close to the base of the Los Coyotes Member. The carbonates of this formation have negative to positive δ13C values (-4.63 to +2.6‰) and highly depleted δ18O values that range from -12.74 to -8.34‰. The absence of correlation between δ13C and δ18O values supports a primary marine origin for the δ13C values of these limestones. The carbon-isotopic curve of the Cerro Pimas stratigraphic section has well-defined δ13C segments (C8 - C15) that compare with published curves of similar age. In the lower part of the early Albian Los Coyotes Member, the presence of OAE 1b is indicated by an increase followed by a decrease in δ13C values, suggesting correlation with the Kilian Event. The middle part of the Los Coyotes Member has a significant negative carbon-isotope excursion correlated with the globally recognizable early Albian Paquier event. Moreover, another significant negative carbon-isotope shift is observed in the upper part of the Los Coyotes Member, which can be correlated with the Leenhardt Event. The occurrence of the Kilian, Paquier and Leenhardt Events (OAE 1b cluster) in the Cerro Pimas stratigraphy confirms the global nature of these early Albian disturbances of the carbon cycle.

Uppermost Cretaceous to middle Oligocene carbon and oxygen isotope stratigraphy of Southwest Pacific : holes 1121B and 1124C, ODP Leg 181

International Nuclear Information System (INIS)

Wei, K.-Y.; Mii, H.-S.; Shu, I-T.; Lin, Y.-J.

2005-01-01

Oxygen and carbon isotopic ratios of bulk sediments from ODP Leg 181, holes 1121B and 1124C, in the Southwest Pacific were measured. The isotopic signals are mainly contributed by calcareous nannofossils with minimal diagenetic alteration. A complete section of the late Paleogene age between 60.7 and 57.5 Ma was recovered from Hole 1121B. However, the Paleogene sedimentary sequence of Hole 1124C was truncated by three major hiatuses: late Paleocene to middle Eocene (59-42 Ma), middle Eocene to early Oligocene (40-33.5 Ma), and early Oligocene to middle Oligocene (31.3-27.5 Ma). The middle Eocene shows the most negative δ 18 O values (c. -0.8 permille) compared to the early Paleocene (c. -0.2 to -0.3 permille) and Oligocene (c. 0.6-0.9 permille). The δ 18 O pattern is consistent with previous understanding of the Paleogene paleoclimate: a warmth optimum in the early-middle Eocene followed by a major glaciation in the early Oligocene at c. 34 Ma. The hiatus of 33.5-40 Ma indicates that the Tasmanian Gateway had deepened enough by 33.5 Ma, allowing the breakthrough of cold, bottom water and consequently the formation of the Deep Western Boundary Current (DWBC). With the aid of independent biochronological and magnetochronological markers, the Paleocene carbon isotopic profiles were correlated with that of DSDP 577 in the North Pacific. Both sites record the early part of the Paleocene carbon isotopic maximum event, while only Hole 1124C extends back to the early Paleocene and latest Cretaceous. A short hiatus of 60.5-62.5 Ma age may exist. Although the Cretaceous/Tertiary boundary is not directly recorded, a significant cooling trend across the boundary is evident. The surface water became warmer after 64.5 Ma, and reached a stable warmth level during 64-59 Ma. A major cooling took place during c. 59-57 Ma in the late Paleocene. The temperature gradients between the two sites (ODP 1121 and 1124, paleolatitudes 64 degrees S versus 53 degrees S) are estimated to be c

Bio-chemostratigraphy of the Barremian-Aptian shallow-water carbonates of the southern Apennines (Italy: pinpointing the OAE1a in a Tethyan carbonate platform

Directory of Open Access Journals (Sweden)

M. Di Lucia

2012-01-01

Full Text Available Low biostratigraphic resolution and lack of chronostratigraphic calibration hinder precise correlations between platform carbonates and coeval deep-water successions. These are the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper carbon and strontium isotope stratigraphy are used to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to this calibration, the segment of decreasing δ¹³C values, leading to the negative peak that is generally taken as the onset of the Selli event, starts a few metres above the last occurrence of Palorbitolina lenticularis and Voloshinoides murgensis. The following rise of δ¹³C values, corresponding to the interval of enhanced accumulation of organic matter in deep-water sections, ends just below the first acme of Salpingoporella dinarica, which roughly corresponds to the segment of peak δ¹³C values. The whole carbon isotope excursion associated with the oceanic anoxic event 1a is bracketed in the Apenninic carbonate platform between the last occurrence of Voloshinoides murgensis and the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana. Since these bioevents have been widely recognized beyond the Apenninic platform, the calibration presented in this paper can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys. This calibration will be particularly useful to interpret the record of the Selli event in carbonate platform sections for which a reliable carbon isotope stratigraphy is not available.

A carbon isotope budget for an anoxic marine sediment

International Nuclear Information System (INIS)

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

1991-01-01

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

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

Science.gov (United States)

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

2017-12-19

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

Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

International Nuclear Information System (INIS)

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

1994-01-01

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

Isotopes in the earth sciences

Energy Technology Data Exchange (ETDEWEB)

Bowen, Robert

1988-01-01

This book examines significant aspects of isotope applications in geology and geochemistry commencing with basic matters, such as atomic structure, stable nuclides and their fractionation, as well as the various decay modes of unstable nuclides. Modern mass spectrometry techniques including electrostatic tandem accelerators are followed by a review of radioisotope dating technology. The relatively new method using the rare earth elements samarium and neodymium are covered. Other geochronometers, applicable to both rocks and minerals not dateable otherwise, are included. A review is given of isotopes in the atmosphere, hydrosphere and lithosphere of the Earth. Those of oxygen and hydrogen together with the cosmogenic radionuclides tritium and radiocarbon are discussed in relation to the biosphere. The role of isotopes of carbon, nitrogen and sulphur is described and extended to fossil fuels and rocks as well as meteorites. Related themes such as Phanerozoic oceans, oceanic palaeothermometry, snow and ice stratigraphy and geothermal waters are covered. The field of isotopic palaeoecology is discussed. Radioactive wastes, their accumulation, dangers and disposal are investigated with especial reference to their environmental impacts.

Hafnium isotope stratigraphy of ferromanganese crusts

Science.gov (United States)

Lee; Halliday; Hein; Burton; Christensen; Gunther

1999-08-13

A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in (87)Sr/(86)Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.

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

Science.gov (United States)

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

2004-01-01

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

Modeling the carbon isotope composition of bivalve shells (Invited)

Science.gov (United States)

Romanek, C.

2010-12-01

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

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

International Nuclear Information System (INIS)

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

1993-01-01

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

Carbon and oxygen isotope compositions of the carbonate facies

Indian Academy of Sciences (India)

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

Biomineralization and the carbon isotope record

International Nuclear Information System (INIS)

Degens, E.T.; Ittekkot, V.; Kazmierczak, J.

1986-01-01

The advent of biomineralization at the turn of the Precambrian/Cambrian boundary has been a major event in the Earth's evolutionary history. With this there has been a major shift from abiotic to biotic formation of minerals such as phosphates and carbonates and, subsequently, silica. The dominant factor which effected this shift is a change in ocean's chemistry with respect to its Ca 2+ and mineral nutrient contents. Mechanism controlling the biotic mineral formation is different from that controlling the abiotic one in that the former is enzymically controlled. It is suggested that this difference is also manifested in the stable carbon isotope fractionation between the two processes and has implication for the interpretation of stable carbon isotope record. (Author)

Influence of chemical structure on carbon isotope composition of lignite

Science.gov (United States)

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

2017-04-01

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

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

International Nuclear Information System (INIS)

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

1990-01-01

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

Short-term measurement of carbon isotope fractionation in plants

International Nuclear Information System (INIS)

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

1986-01-01

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

Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

International Nuclear Information System (INIS)

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

1982-01-01

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

Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

Energy Technology Data Exchange (ETDEWEB)

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

1982-02-10

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

Measurement of stable isotope ratio of organic carbon in water samples

International Nuclear Information System (INIS)

Fujii, Toshihiro; Otsuki, Akira

1977-01-01

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

Stable-carbon isotope variability in tree foliage and wood

International Nuclear Information System (INIS)

Leavitt, S.W.; Long, A.

1986-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-06-15

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

Chromium isotope fractionation during coprecipitation with calcium carbonate

DEFF Research Database (Denmark)

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

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

Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

Science.gov (United States)

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

2012-12-01

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

Study on quaternary stratigraphy and environmental changes in South Sea, Korea

Energy Technology Data Exchange (ETDEWEB)

Chang, Jeong-Hae; Lee, Chi-Won; Kim, Sung-Pil [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

1999-12-01

According to interpretation of seismic profiles crossing the drilled sites, there are five sequences, namely Unit I, Unit II, Unit III, Unit IV and Unit V from bottom, separable by a reflector with good lateral continuity. If we apply the conception of sequential stratigraphy to the sea level fluctuation caused depositional processes, based on the results of seismic profiles, it will be possible to figure out the late Quaternary depositional processes in the context of sea level changes. According to the sedimentological and seismic stratigraphic analysis, most of SSDP sites showed transgression and regression sequences. Chemical analyses of elements for the sediment samples of SSDP-102 core exhibit the geochemical factors which may influenced the sedimentary environments of the study area. The lower-most sedimentary sequence Unit III can be interpreted as an environment which was influenced dominantly by stronger chemical weathering under a semi-fresh water environment. Based on predominance of carbonate-originated Ca in the homogeneous mud sequence, a high productive surface water along with transgression may have controlled the upper-most sedimentary sequence Unit I. Scatter diagram represents oxygen and carbon isotopic values of benthic foraminifera (Asterorotalia concinna) which is analyzed. All 61 points has value between +1 and -1. If isotopic values of selected benthic foraminifera are equilibrium with surrounding values. These distributions indicate transitional between coastal environment affected by fresh water and open marine environment. (author). 24 refs., 8 tabs., 25 figs.

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

Science.gov (United States)

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

2011-12-01

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

Robust optical carbon dioxide isotope analyzer, Phase I

Data.gov (United States)

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

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.

Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

Science.gov (United States)

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

2013-12-01

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

Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

International Nuclear Information System (INIS)

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

2007-01-01

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

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

Science.gov (United States)

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

2016-02-01

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

Integrated stratigraphy and astronomical tuning of Smirra cores, lower Eocene, Umbria-Marche basin, Italy.

Science.gov (United States)

Lauretano, Vittoria; Turtù, Antonio; Hilgen, Frits; Galeotti, Simone; Catanzariti, Rita; Reichart, Gert Jan; Lourens, Lucas J.

2016-04-01

The early Eocene represents an ideal case study to analyse the impact of increase global warming on the ocean-atmosphere system. During this time interval, the Earth's surface experienced a long-term warming trend that culminated in a period of sustained high temperatures called the Early Eocene Climatic Optimum (EECO). These perturbations of the ocean-atmosphere system involved the global carbon cycle and global temperatures and have been linked to orbital forcing. Unravelling this complex climatic system strictly depends on the availability of high-quality suitable geological records and accurate age models. However, discrepancies between the astrochronological and radioisotopic dating techniques complicate the development of a robust time scale for the early Eocene (49-54 Ma). Here we present the first magneto-, bio-, chemo- and cyclostratigraphic results of the drilling of the land-based Smirra section, in the Umbria Marche Basin. The sediments recovered at Smirra provide a remarkably well-preserved and undisturbed succession of the early Palaeogene pelagic stratigraphy. Bulk stable carbon isotope and X-Ray Fluorescence (XRF) scanning records are employed in the construction of an astronomically tuned age model for the time interval between ~49 and ~54 Ma based on the tuning to long-eccentricity. These results are then compared to the astronomical tuning of the benthic carbon isotope record of ODP Site 1263 to evaluate the different age model options and improve the time scale of the early Eocene by assessing the precise number of eccentricity-related cycles comprised in this critical interval.

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.

Temperature dependence of carbon isotope fractionation in CAM plants

International Nuclear Information System (INIS)

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

1985-01-01

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

Temperature dependence of carbon isotope fractionation in CAM plants

Energy Technology Data Exchange (ETDEWEB)

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

1985-09-01

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

Oxygen isotope calibration of the onset of ice-rafting and history of glaciation in the North Atlantic region

Science.gov (United States)

Shackleton, N.J.; Backman, J.; Zimmerman, H.; Kent, D.V.; Hall, M.A.; Roberts, David G.; Schnitker, D.; Baldauf, J.G.; Desprairies, A.; Homrighausen, R.; Huddlestun, P.; Keene, J.B.; Kaltenback, A.J.; Krumsiek, K.A.O.; Morton, A.C.; Murray, J.W.; Westberg-Smith, J.

1984-01-01

We report here that DSDP Site 552A, cored with the hydraulic piston corer on the west flank of Rockall Bank, recovered an undisturbed sequence of alternating white deep-sea carbonate oozes and dark-coloured layers that are rich in glacial debris. Oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice-rafting occurred at about 2.4 Myr, and was preceded by a minor pulse of ice-rafting at about 2.5 Myr. The carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present-day North Atlantic deep water at least since 3.5 Myr. ?? 1984 Nature Publishing Group.

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

International Nuclear Information System (INIS)

Takeshita, Kenji; Kitamoto, Asashi

1985-01-01

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

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

Science.gov (United States)

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

2008-07-01

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

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

Science.gov (United States)

Bowen, G. J.; Abels, H.

2015-12-01

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

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

Modeling of the global carbon cycle - isotopic data requirements

International Nuclear Information System (INIS)

Ciais, P.

1994-01-01

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

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Forensic utility of the carbon isotope ratio of PVC tape backings

Science.gov (United States)

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

2008-12-01

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

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.

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

Science.gov (United States)

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

2017-08-01

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

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

International Nuclear Information System (INIS)

Torquato, J.R.F.

1980-01-01

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

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

DEFF Research Database (Denmark)

Hesselbo, Stephen P.; Korte, Christoph

2010-01-01

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

Biological fractionation of oxygen and carbon isotopes by recent benthic foraminifera

International Nuclear Information System (INIS)

Woodruff, F.; Douglas, R.G.

1980-01-01

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

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

International Nuclear Information System (INIS)

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

2009-01-01

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

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

Science.gov (United States)

Price, Gregory; Grimes, Stephen

2015-04-01

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

CO2-dependent carbon isotope fractionation in the dinoflagellate Alexandrium tamarense

Science.gov (United States)

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

2017-09-01

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

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

International Nuclear Information System (INIS)

O'Leary, M.H.

1988-01-01

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

What Drives Carbon Isotope Fractionation by the Terrestrial Biosphere?

Science.gov (United States)

Still, Christopher; Rastogi, Bharat

2017-11-01

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

A carbon isotope challenge to the snowball Earth.

Science.gov (United States)

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

2011-10-05

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

Monitoring in situ biodegradation of hydrocarbons by using stable carbon isotopes

International Nuclear Information System (INIS)

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

1991-01-01

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

New Carbonate Standard Reference Materials for Boron Isotope Geochemistry

Science.gov (United States)

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

2015-12-01

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

Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces

Directory of Open Access Journals (Sweden)

Shaena Montanari

2017-06-01

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

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

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

CERN Document Server

Franberg, Hanna; Köster, Ulli; Ammann, Markus

2008-01-01

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

Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-01

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

Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

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

International Nuclear Information System (INIS)

Lazeeva, G.S.

1986-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-05-05

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Science.gov (United States)

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

2003-12-01

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

Carboniferous-Permian sedimentology and stratigraphy of the Nordfjorden High and Loppa Spur, Arctic Norway

DEFF Research Database (Denmark)

Ahlborn, Morten

Abstract (shortened) Facies analysis of Late Paleozoic warm-water carbonates, were conducted in order to investigate the depositional evolution, cyclicity, internal architecture and sequence stratigraphy of the upper Gipsdalen Group carbonate platform on the Nordfjorden High in central Spitsberge...

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

International Nuclear Information System (INIS)

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

1985-01-01

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

Carbon Isotope Chemistry in Molecular Clouds

Science.gov (United States)

Robertson, Amy N.; Willacy, Karen

2012-01-01

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

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

Science.gov (United States)

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

1985-01-01

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

Carbon cycle history through the Middle Jurassic (Aalenian - Bathonian) of the Mecsek Mountains, Southern Hungary

Science.gov (United States)

Price, Gregory D.; Főzy, István; Galácz, András

2018-04-01

A carbonate carbon isotope curve from the Aalenian-Bathonian interval is presented from the Óbánya valley, of the Mecsek Mountains, Hungary. This interval is certainly less well constrained and studied than other Jurassic time slices. The Óbánya valley lies in the eastern part of the Mecsek Mountains, between Óbánya and Kisújbánya and provides exposures of an Aalenian to Lower Cretaceous sequence. It is not strongly affected by tectonics, as compared to other sections of eastern Mecsek of the same age. In parts, a rich fossil assemblage has been collected, with Bathonian ammonites being especially valuable at this locality. The pelagic Middle Jurassic is represented by the Komló Calcareous Marl Formation and thin-bedded limestones of the Óbánya Limestone Formation. These are overlain by Upper Jurassic siliceous limestones and radiolarites of the Fonyászó Limestone Formation. Our new data indicate a series of carbon isotope anomalies within the late Aalenian and early-middle Bajocian. In particular, analysis of the Komló Calcareous Marl Formation reveals a negative carbon isotope excursion followed by positive values that occurs near the base of the section (across the Aalenian-Bajocian boundary). The origin of this carbon-isotope anomaly is interpreted to lie in significant changes to carbon fluxes potentially stemming from reduced run off, lowering the fertility of surface waters which in turn leads to lessened primary production and a negative δ13C shift. These data are comparable with carbonate carbon isotope records from other Tethyan margin sediments. Our integrated biostratigraphy and carbon isotope stratigraphy enable us to improve stratigraphic correlation and age determination of the examined strata. Therefore, this study of the Komló Calcareous Marl Formation confirms that the existing carbon isotope curves serve as a global standard for Aalenian-Bathonian δ13C variation.

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

Science.gov (United States)

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

2013-01-01

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

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

OpenAIRE

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

2014-01-01

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

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

Science.gov (United States)

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

2015-11-01

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

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

Science.gov (United States)

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

2017-12-01

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

Relationships between tree height and carbon isotope discrimination

Science.gov (United States)

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

2011-01-01

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

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

International Nuclear Information System (INIS)

Iben, I. Jr.

1984-01-01

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

Volcanic stratigraphy: A review

Science.gov (United States)

Martí, Joan; Groppelli, Gianluca; Brum da Silveira, Antonio

2018-05-01

Volcanic stratigraphy is a fundamental component of geological mapping in volcanic areas as it yields the basic criteria and essential data for identifying the spatial and temporal relationships between volcanic products and intra/inter-eruptive processes (earth-surface, tectonic and climatic), which in turn provides greater understanding of the geological evolution of a region. Establishing precise stratigraphic relationships in volcanic successions is not only essential for understanding the past behaviour of volcanoes and for predicting how they might behave in the future, but is also critical for establishing guidelines for exploring economic and energy resources associated with volcanic systems or for reconstructing the evolution of sedimentary basins in which volcanism has played a significant role. Like classical stratigraphy, volcanic stratigraphy should also be defined using a systematic methodology that can provide an organised and comprehensive description of the temporal and spatial evolution of volcanic terrain. This review explores different methods employed in studies of volcanic stratigraphy, examines four case studies that use differing stratigraphic approaches, and recommends methods for using systematic volcanic stratigraphy based on the application of the concepts of traditional stratigraphy but adapted to the needs of volcanological environment.

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

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

Science.gov (United States)

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

2007-12-01

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

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-09-01

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

Soil Carbon: Compositional and Isotopic Analysis

Energy Technology Data Exchange (ETDEWEB)

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

2016-11-01

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

Revisiting the Ceara Rise, equatorial Atlantic Ocean: isotope stratigraphy of ODP Leg 154

Science.gov (United States)

Wilkens, Roy; Drury, Anna Joy; Westerhold, Thomas; Lyle, Mitchell; Gorgas, Thomas; Tian, Jun

2017-04-01

Isotope stratigraphy has become the method of choice for investigating both past ocean temperatures and global ice volume. Lisiecki and Raymo (2005) published a stacked record of 57 globally distributed benthic δ18O records versus age (LR04 stack). In this study LR04 is compared to high resolution records collected at all of the sites drilled during Ocean Drilling Program (ODP) Leg 154 on the Ceara Rise, in the western equatorial Atlantic Ocean. Newly developed software - the Code for Ocean Drilling Data (CODD) - is used to check data splices of the Ceara sites and better align out-of-splice data with in-splice data. CODD allows to depth and age scaled core images recovered from core table photos enormously facilitating data analysis. The entire splices of ODP Sites 925, 926, 927, 928 and 929 were reviewed. Most changes were minor although several large enough to affect age models based on orbital tuning. We revised the astronomically tuned age model for the Ceara Rise by tuning darker, more clay rich layers to Northern Hemisphere insolation minima. Then we assembled a regional composite benthic stable isotope record from published data. This new Ceara Rise stack provides a new regional reference section for the equatorial Atlantic covering the last 5 million years with an independent age model compared to the non-linear ice volume models of the LR04 stack. Comparison shows that the benthic δ18O composite is consistent with the LR04 stack from 0 - 4 Ma despite a short interval between 1.80 and 1.90 Ma, where LR04 exhibits 2 maxima but where Ceara Rise contains only 1. The interval between 4.0 and 4.5 Ma in the Ceara Rise compilation is decidedly different from LR04, reflecting both the low amplitude of the signal over this interval and the limited amount of data available for the LR04 stack. Our results also point out that precession cycles have been misinterpreted as obliquity in the LR04 stack as suggested by the Ceara Rise composite at 4.2 Ma.

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

Directory of Open Access Journals (Sweden)

A. Jahn

2015-08-01

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

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

Science.gov (United States)

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

2015-08-01

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

Boron isotope fractionation in magma via crustal carbonate dissolution.

Science.gov (United States)

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

2016-08-04

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

Boron isotope fractionation in magma via crustal carbonate dissolution

Science.gov (United States)

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

2016-08-01

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

Carbon isotope ratios in field Population II giant stars

International Nuclear Information System (INIS)

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

1986-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

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

NARCIS (Netherlands)

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

2002-01-01

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

Monitoring of carbon isotope composition of snow cover for Tomsk region

Science.gov (United States)

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

2016-11-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Rustad, James R.; Zarzycki, Piotr

2008-07-29

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

Astronomical tuning and carbon isotope stratigraphy of the Maastrichtian in Sopelana and Zumaia (Basque country, N-Spain)

Science.gov (United States)

Batenburg, S. J.; Gale, A. S.; Hilgen, F. J.; Hüsing, S. K.; Laskar, J.; Orue-Etxebarria, X.; Sprovieri, M.; Voigt, S.

2012-04-01

Astronomical tuning has led to significant refinement of the Geological Time Scale for the Cenozoic, however the Late Cretaceous time scale still has potential errors of ~0.5 Myr. The Basque sections of Sopelana and Zumaia (N-Spain) provide a high-resolution sedimentary archive encompassing the Maastrichtian up to the Cretaceous/Paleogene boundary. Rhythmic limestone-marl alternations, deposited in a hemipelagic setting, reflect the influence of the periodicities of eccentricity modulated precession. Starting from a K/Pg boundary age of 66.0 Ma, consecutive 405-kyr minima are tuned to the new astronomical solution La2011. This orbital tuning, together with the expression of individual precessional cycles, allows for unprecedented refinement of the Geologic Time Scale for the Maastrichtian with errors analysis of magnetic susceptibility and colour reflectance data. A cyclostratigraphic framework and orbital tuning of the Zumaia section has recently been obtained. This is extended further back in time by correlation to the Sopelana section by recognition of orbital patterns and marker beds. The total amount of time represented by the two sections is 5 Myr. The lower boundary falls within chron C32N1n, almost reaching the Campanian/Maastrichtian boundary. Magnetostratigraphic and biostratigraphic data allow for application of the cyclostratigraphic framework worldwide, and comparison to previously published Maastrichtian time scales. Additionally, we present an orbitally tuned bulk carbon isotope curve. The high resolution and large amplitude of shifts in δ13C on the 405-kyr and 1.2-Myr scales enables correlation to deep marine oceanic sites, several sections from the Boreal chalk sea and Italy and, importantly, the Campanian/Maastrichtian boundary GSSP at Tercis, France. This will provide a globally applicable cyclostratigraphic framework for the entire Maastrichtian. We will discuss the implications for the orbital pacing theory of the late Cretaceous climate

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

Science.gov (United States)

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

2016-01-01

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

Mars Stratigraphy Mission

Science.gov (United States)

Budney, C. J.; Miller, S. L.; Cutts, J. A.

2000-01-01

The Mars Stratigraphy Mission lands a rover on the surface of Mars which descends down a cliff in Valles Marineris to study the stratigraphy. The rover carries a unique complement of instruments to analyze and age-date materials encountered during descent past 2 km of strata. The science objective for the Mars Stratigraphy Mission is to identify the geologic history of the layered deposits in the Valles Marineris region of Mars. This includes constraining the time interval for formation of these deposits by measuring the ages of various layers and determining the origin of the deposits (volcanic or sedimentary) by measuring their composition and imaging their morphology.

Distinguishing ectomycorrhizal and saprophytic fungi using carbon and nitrogen isotopic compositions

Directory of Open Access Journals (Sweden)

Weiguo Hou

2012-05-01

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

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.

Stable isotope stratigraphy of Latest Miocene sequences in northwest Morocco: The Bou Regreg section

Science.gov (United States)

Hodell, David A.; Benson, Richard H.; Kennett, James P.; Rakic-El Bied, Kruna

1989-08-01

Oxygen and carbon isotopic ratios of foraminifers were measured from outcrop and drill core sequences from the Bou Regreg Section, northwest Morocco. This composite section was located at the western end of the Rifian Corridor during the late Miocene and thus potentially contains a record of water exchange between the Atlantic and Mediterranean during the late Tortonian and Messinian stages. Here we correlate isotopic and sedimentologic events in the Bou Regreg Section with Mediterranean and deep-sea sequences during the time leading up to and including the deposition of the Messinian evaporites. The late Miocene chron 6 carbon shift was identified in two Moroccan sequences, providing a valuable 6.3-Ma datum level. In both sections, the carbon shift coincides with the first occurrence of Globorotalia conomiozea and the Tortonian/Messinian boundary. Near this boundary, a major faunal turnover occurred in ostracod, planktonic foraminiferal, and nannofossil assemblages that indicates a cooling of surface and deep water in the Rifian Corridor. At 6.1 Ma, just above the Tortonian/Messinian boundary, mean ∂18O values of benthic foraminifers increased by 0.4-0.5‰ suggesting decreased temperature and/or increased continental ice volume. The faunal and isotopic changes are interpreted as reflecting a reversal in the direction of deep water flow through the Rifian Corridor that occurred between 6.3 and 6.1 Ma. At this time, cold, nutrient-rich waters filled the Mediterranean basins from intermediate depths of the Atlantic, and the production of Mediterranean Outflow Water ceased. The upwelling of nutrient-rich Atlantic intermediate water stimulated productivity in the Mediterranean, which led to the deposition of organic-rich strata such as those found in the Tripoli Formation. At ˜5.5 Ma, coincident with a coiling shift in Neogloboquadrina acostaensis, the variability of the benthic ∂18O signal increased markedly, and strong color variations appeared in the sediments

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-15

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

Stable isotope stratigraphy and larger benthic foraminiferal extinctions in the Melinau Limestone, Sarawak

Science.gov (United States)

Cotton, Laura J.; Pearson, Paul N.; Renema, Willem

2014-01-01

Important long-ranging groups of larger benthic foraminifera (LBF) are known to have become extinct during a period of global cooling and climate disruption at the Eocene-Oligocene transition (EOT) but the precise timing and mechanisms are uncertain. Recent study showed unexpectedly that the LBF extinction in Tanzania occurs very close to the Eocene/Oligocene boundary, as recognised by the extinction of the planktonic foraminiferal Family Hantkeninidae, rather than at the later period of maximum global ice growth and sea-level fall, as previously thought. Here we investigate the same phase of extinction in the Melinau Limestone of Sarawak, on the island of Borneo, Malaysia one of the most complete carbonate successions spanning the Eocene to Lower Miocene. Assemblages of LBF from the Melinau Limestone were studied extensively by Geoffrey Adams during the 1960s-80s, confirming a major extinction during the EOT, but the section lacked independent means of correlation. By analysing rock samples originally studied by Adams and now in the Natural History Museum, London, we provide new bulk stable isotope (δ13C and δ18O) records. This enables us to identify, albeit tentatively, the level of maximum stable isotope excursion and show that the LBF extinction event in the Melinau Limestone occurs below this isotope excursion, supporting the results from Tanzania and indicating that the extinction of LBF close to the Eocene/Oligocene boundary may be a global phenomenon.

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

Science.gov (United States)

Uchikawa, J.; Zeebe, R. E.

2011-12-01

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

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.

Control strategies for laser separation of carbon isotopes

Indian Academy of Sciences (India)

Unknown

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

Influence of diet on the distribution of carbon isotopes in animals

International Nuclear Information System (INIS)

DeNiro, M.J.; Epstein, S.

1978-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1981-01-01

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

Soil drying effects on the carbon isotope composition of soil respiration

Science.gov (United States)

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

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

Science.gov (United States)

Bukata, Andrew R; Kyser, T Kurtis

2007-02-15

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

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

International Nuclear Information System (INIS)

Aravena, R.; Dinel, H.

1993-01-01

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

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

Science.gov (United States)

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

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

Science.gov (United States)

Hassan, Afifa Afifi

1982-01-01

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

Isotopic Hg in an Allende carbon-rich residue

Science.gov (United States)

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

1990-01-01

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

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

International Nuclear Information System (INIS)

Ishizuka, Toshio

1978-01-01

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

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

Science.gov (United States)

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

2015-01-06

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

Carbon isotope analysis in apple nectar beverages

Directory of Open Access Journals (Sweden)

Ricardo Figueira

2013-03-01

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

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

NARCIS (Netherlands)

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

2013-01-01

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

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

International Nuclear Information System (INIS)

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

1977-01-01

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

Carbon cycle history through the Middle Jurassic (Aalenian – Bathonian of the Mecsek Mountains, Southern Hungary

Directory of Open Access Journals (Sweden)

Price Gregory D.

2018-04-01

Full Text Available A carbonate carbon isotope curve from the Aalenian–Bathonian interval is presented from the Óbánya valley, of the Mecsek Mountains, Hungary. This interval is certainly less well constrained and studied than other Jurassic time slices. The Óbánya valley lies in the eastern part of the Mecsek Mountains, between Óbánya and Kisújbánya and provides exposures of an Aalenian to Lower Cretaceous sequence. It is not strongly affected by tectonics, as compared to other sections of eastern Mecsek of the same age. In parts, a rich fossil assemblage has been collected, with Bathonian ammonites being especially valuable at this locality. The pelagic Middle Jurassic is represented by the Komló Calcareous Marl Formation and thin-bedded limestones of the Óbánya Limestone Formation. These are overlain by Upper Jurassic siliceous limestones and radiolarites of the Fonyászó Limestone Formation. Our new data indicate a series of carbon isotope anomalies within the late Aalenian and early-middle Bajocian. In particular, analysis of the Komló Calcareous Marl Formation reveals a negative carbon isotope excursion followed by positive values that occurs near the base of the section (across the Aalenian–Bajocian boundary. The origin of this carbon-isotope anomaly is interpreted to lie in significant changes to carbon fluxes potentially stemming from reduced run off, lowering the fertility of surface waters which in turn leads to lessened primary production and a negative δ13C shift. These data are comparable with carbonate carbon isotope records from other Tethyan margin sediments. Our integrated biostratigraphy and carbon isotope stratigraphy enable us to improve stratigraphic correlation and age determination of the examined strata. Therefore, this study of the Komló Calcareous Marl Formation confirms that the existing carbon isotope curves serve as a global standard for Aalenian–Bathonian δ13C variation.

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

International Nuclear Information System (INIS)

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

2012-01-01

CO 2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO 2 carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO 2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of C-13 in CO 2 . Using a set of reference gases of known CO 2 concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO 2 concentration, and 0.05 per thousand for δC-13 at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of C-13 on CO 2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO 2 concentration and 1.3 per thousand for δC-13, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO 2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source. (authors)

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

International Nuclear Information System (INIS)

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

1976-01-01

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

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

Indian Academy of Sciences (India)

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

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

Science.gov (United States)

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

2003-12-01

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

Stable carbon isotope biogeochemistry of lakes along a trophic gradient

NARCIS (Netherlands)

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

2014-01-01

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

C isotope fractionation during heterotrophic activity driven carbonate precipitation

Science.gov (United States)

Balci, Nurgul; Demirel, Cansu

2016-04-01

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

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

International Nuclear Information System (INIS)

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

2008-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-01-01

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

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

International Nuclear Information System (INIS)

2002-01-01

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

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

Science.gov (United States)

Zong, Yutong; Xiao, Qing; Lu, Shenggao

2018-02-01

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

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

Science.gov (United States)

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

2017-03-01

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

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

Science.gov (United States)

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

2014-01-01

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

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.

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.

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

Directory of Open Access Journals (Sweden)

Dorota Porowska

2015-10-01

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

Application of carbon isotope analyses in food technology

International Nuclear Information System (INIS)

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

2001-01-01

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

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

Science.gov (United States)

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

2018-02-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-05-15

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

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

International Nuclear Information System (INIS)

Qi Biao; Ding Lingling; Cui Jiehua; Wang Yanhong

2009-01-01

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

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

OpenAIRE

Petach, Tanya N.

2015-01-01

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

3. South American symposium on isotope geology. Extended abstracts

International Nuclear Information System (INIS)

2001-10-01

This publication include papers in the fields on Methodology, thermochronology, and geochronology; Evolution of cratonic South America; Magmatic processes; Environmental geology, hydrogeology, isotopic stratigraphy and paleoclimatology; Economic Geology and Evolution of the Andean margin of South America

Towards a climate event stratigraphy for New Zealand over the past 30,000 years

International Nuclear Information System (INIS)

Barrell, D.J.A.; Alloway, B.V.; Shulmeister, J.; Newnham, R.M.

2005-01-01

A poster summarizing a representative selection of evidence for environmental conditions and climate change in New Zealand during the last 30,000 years has been prepared as a 'first-step' contribution to the INTIMATE (INTegration of Ice-core, Marine and TerrEstrial records) initiative of the INQUA Paleoclimate Commission. This international initiative aims to establish a more detailed knowledge of the nature, timing and regional to global extent of climatic and environmental changes associated with the Last Termination. The poster depicts key New Zealand onshore and offshore records for the Last Glacial Maximum and the Last Glacial-Interglacial Transition, from a variety of latitudes and elevations. Inset maps show New Zealand's oceanographic setting, principal currents and water masses, extent of glaciers, and distribution of vegetation zones at approximately 22,000 calendar years ago and at modern times (incorporating the inferred vegetation distribution at c. 1250 AD, before deforestation associated with human settlement). A calendar-age timescale is based on a combination of volcanic ash (tephra) and radiometric dates. Paleoclimate records from ice cores from Antarctica and Greenland are presented for comparison with New Zealand records. High-resolution records are presented for sediment-filled volcanic craters in Auckland (total carbon, carbon isotopes and pollen), wetlands in northeast North Island, central North Island and western South Island (pollen), marine sediments off eastern North Island (oxygen isotopes), and stalagmites in caves in northwest South Island (carbon and oxygen isotopes). In addition, the poster includes a range of lower resolution or fragmentary records of climate events, based on glacial landforms and deposits (central Southern Alps, South Island), river terraces and deposits, loess deposits (eastern North and South Islands), and Aeolian quartz silt in non-quartzose, loess-like, andesitic tephric deposits of western North Island. The

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

Science.gov (United States)

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

2017-11-01

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

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

Directory of Open Access Journals (Sweden)

N. Brüggemann

2011-11-01

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

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

Directory of Open Access Journals (Sweden)

R. Schneider

2013-11-01

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

Descriptions of carbon isotopes within the energy density functional theory

International Nuclear Information System (INIS)

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

2014-01-01

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

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

International Nuclear Information System (INIS)

Tagami, Keiko; Uchida, Shigeo

2008-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1984-07-01

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

Isotopic Hg in an Allende carbon-rich residue

International Nuclear Information System (INIS)

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

1990-01-01

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

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

Science.gov (United States)

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C)

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Husson, Dorothée; Harlou, Rikke

2012-01-01

An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and d13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate d13C events and nannofossil bio-events...

Biostratigraphy and sequence stratigraphy of the Sarvak Formation at Fahliyan Anticline (South of Yasuj)

International Nuclear Information System (INIS)

Ahmadi, A.; Vaziri-Moghaddam, A.; Sayrafian, A.; Taheri, A.

2016-01-01

In this study, bio stratigraphy, depositional environment and sequence stratigraphy of the Sarvak Formation at Fahliyan Anticline was studied. 8 species of benthic foraminifera (4 genera) and 8 species of planktonic foraminifera (11 genera) in the study area were recognized. 6 biozones have been recognized by distribution of the foraminifera, which in stratigraphic order are: Favusella washitensis Zone, Orbitolina-Alveolinids Assemblage Zone, Rudist debris Zone, Oligostegina flood Zone, Whiteinella archaeocretacea Zone and Helvetoglobotruncana helvetica Zone. On the basis of these, the age of Albian–Turonian was considered for the Sarvak Formation. Based on petrography and analysis of microfacies features 9 different microfacies types have been recognized, which can be grouped into 3 depositional environments: lagoon, shoal and open marine. The Sarvak Formation represents sedimentation on a carbonate ramp. Sequence stratigraphy analysis led to identification of 4 third-order sequences.

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-05-15

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

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

Science.gov (United States)

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

2015-04-01

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

Paleozoic stratigraphy of two areas in southwestern Indiana

International Nuclear Information System (INIS)

Droste, J.B.

1976-09-01

Two areas recommended for evaluation as solid waste disposal sites lie along the strike of Paleozoic rocks in southwestern Indiana. Thin Pennsylvanian rocks and rocks of the upper Mississippian are at the bedrock surface in maturely dissected uplands in both areas. The gross subsurface stratigraphy beneath both areas is the same, but facies and thickness variation in some of the subsurface Paleozoic units provide for some minor differences between the areas. Thick middle Mississippi carbonates grade downward into clastics of lower Mississippian (Borden Group) and upper Devonian (New Albany Shale) rocks. Middle Devonian and Silurian rocks are dominated by carbonate lithologies. Upper Ordovician (Maquoketa Group) overly carbonates of middle Ordovician age. Thick siltstone and shale of the Borden Group-New Albany Shale zone and Maquoketa Group rocks should be suitable for repository development

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

Science.gov (United States)

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

2009-01-01

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

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

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

Soil moisture effects on the carbon isotopic composition of soil respiration

Science.gov (United States)

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

Carbon isotopes and concentrations in mid-oceanic ridge basalts

International Nuclear Information System (INIS)

Pineau, F.; Javoy, M.

1983-01-01

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

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

Science.gov (United States)

Vieira, Veronica

1997-01-01

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

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

Science.gov (United States)

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

2018-03-01

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

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

Science.gov (United States)

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

2006-12-01

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

Descriptions of carbon isotopes within the energy density functional theory

Energy Technology Data Exchange (ETDEWEB)

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

2014-10-24

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

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

Science.gov (United States)

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

2000-12-01

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

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

Science.gov (United States)

Porowska, Dorota

2015-05-01

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

Revisiting the Ceara Rise, equatorial Atlantic Ocean: isotope stratigraphy of ODP Leg 154 from 0 to 5 Ma

Science.gov (United States)

Wilkens, Roy H.; Westerhold, Thomas; Drury, Anna J.; Lyle, Mitchell; Gorgas, Thomas; Tian, Jun

2017-07-01

Isotope stratigraphy has become the method of choice for investigating both past ocean temperatures and global ice volume. Lisiecki and Raymo (2005) published a stacked record of 57 globally distributed benthic δ18O records versus age (LR04 stack). In this study LR04 is compared to high-resolution records collected at all of the sites drilled during ODP Leg 154 on the Ceara Rise, in the western equatorial Atlantic Ocean. Newly developed software is used to check data splices of the Ceara Rise sites and better align out-of-splice data with in-splice data. Core images recovered from core table photos are depth and age scaled and greatly assist in the data analysis. The entire splices of ODP sites 925, 926, 927, 928 and 929 were reviewed. Most changes were minor although several were large enough to affect age models based on orbital tuning. A Ceara Rise composite record of benthic δ18O is out of sync with LR04 between 1.80 and 1.90 Ma, where LR04 exhibits two maxima but Ceara Rise data contain only one. The interval between 4.0 and 4.5 Ma in the Ceara Rise compilation is decidedly different from LR04, reflecting both the low amplitude of the signal over this interval and the limited amount of data available for the LR04 stack. A regional difference in benthic δ18O of 0.2 ‰ relative to LR04 was found. Independent tuning of Site 926 images and physical property data to the Laskar et al. (2004) orbital solution and integration of available benthic stable isotope data from the Ceara Rise provides a new regional reference section for the equatorial Atlantic covering the last 5 million years.

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.

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

Science.gov (United States)

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

2017-12-01

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

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

NARCIS (Netherlands)

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

2014-01-01

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

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

Science.gov (United States)

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

2015-01-01

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

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

International Nuclear Information System (INIS)

Maass, J.

1981-01-01

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

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

Science.gov (United States)

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

2017-02-01

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

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

Directory of Open Access Journals (Sweden)

H. Graven

2017-12-01

Full Text Available The isotopic composition of carbon (Δ14C and δ13C in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850–2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6 for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

Science.gov (United States)

Graven, Heather; Allison, Colin E.; Etheridge, David M.; Hammer, Samuel; Keeling, Ralph F.; Levin, Ingeborg; Meijer, Harro A. J.; Rubino, Mauro; Tans, Pieter P.; Trudinger, Cathy M.; Vaughn, Bruce H.; White, James W. C.

2017-12-01

The isotopic composition of carbon (Δ14C and δ13C) in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850-2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

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

International Nuclear Information System (INIS)

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

1991-01-01

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

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

Science.gov (United States)

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

2018-05-01

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

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

Science.gov (United States)

Warwick, Peter D.; Ruppert, Leslie F.

2016-01-01

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

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

The thermal history of char as disclosed by carbon isotope ratios

DEFF Research Database (Denmark)

Egsgaard, Helge; Ambus, Per; Ahrenfeldt, Jesper

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

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

International Nuclear Information System (INIS)

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

1993-01-01

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

Control strategies for laser separation of carbon isotopes

Indian Academy of Sciences (India)

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

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

International Nuclear Information System (INIS)

Helie, J-F

2009-01-01

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

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

Science.gov (United States)

Hodgin, E. B.

2015-12-01

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

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

International Nuclear Information System (INIS)

Sun Fengmei; Yu Hongxia; Wu Wei; Yang Shuming

2009-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1984-01-01

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

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

Science.gov (United States)

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

2015-04-01

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

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

International Nuclear Information System (INIS)

Guo Qingjun; Liu Congqiang; Harald Strauss; Tatiana Goldberg

2003-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

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

International Nuclear Information System (INIS)

LaZerte, B.D.

1983-01-01

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

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

International Nuclear Information System (INIS)

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

1998-01-01

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

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

NARCIS (Netherlands)

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

2017-01-01

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

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

DEFF Research Database (Denmark)

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

2011-01-01

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

Soil moisture effects on the carbon isotope composition of soil respiration

Science.gov (United States)

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

2010-01-01

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

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

International Nuclear Information System (INIS)

Stemmerik, L.; Magaritz, M.

1989-01-01

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

A carbon isotope survey of South African honey

International Nuclear Information System (INIS)

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

1987-01-01

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

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

International Nuclear Information System (INIS)

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

1981-01-01

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

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

Science.gov (United States)

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

2007-01-01

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

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

Science.gov (United States)

Goevert, Dennis; Conrad, Ralf

2008-11-01

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

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

DEFF Research Database (Denmark)

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

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

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

Science.gov (United States)

Jin, Biao; Nijenhuis, Ivonne; Rolle, Massimo

2018-06-01

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

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

Directory of Open Access Journals (Sweden)

J. Jung

2011-11-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2002-07-01

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

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

International Nuclear Information System (INIS)

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

1988-01-01

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

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

NARCIS (Netherlands)

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

2004-01-01

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

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

International Nuclear Information System (INIS)

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

2002-01-01

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

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

International Nuclear Information System (INIS)

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

1985-01-01

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

Diamond carbon sources: a comparison of carbon isotope models

International Nuclear Information System (INIS)

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

1990-01-01

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

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

Science.gov (United States)

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

2015-08-01

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

High-resolution C and O stable isotope geochemistry of the early Aptian OAE1a at Cau (Prebetic Zone, Spain): Preliminary results from sediment core.

Science.gov (United States)

Alejandro Ruiz-Ortiz, Pedro; Aguado, Roque; Castro, José Manuel; Gallego, David; de Gea, Ginés Alfonso; Jarvis, Ian; Molina, José Miguel; Nieto, Luis Miguel; Pancost, Richard; Quijano, María Luisa; Reolid, Matías; Rodriguez, Rafael; Skelton, Peter; Weisser, Helmut

2017-04-01

The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. The Aptian OAE1a (120 Ma), represents an excellent example, recorded in all the main ocean basins, associated to massive burial of organic matter in marine sediments [1]. Much research has been done on the OAE1a from different sections in the world over the last decades, including the definition of the C-isotope stratigraphy of the event [2]. Notwithstanding, higher-resolution studies across the entire event will be crucial to shed light into the precise timing and rates of the different environmental and biotic changes that occurred. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian palaeomargin. The Lower Aptian of the Cau section is represented by a hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous studies of the Lower Aptian of the Cau section have focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry [3], [4], and in the reconstruction of pCO2 from organic geochemistry proxies [5]. All these studies reveal that the Cau section represents an excellent site to investigate the OAE 1a, based on its unusual high thickness and stratigraphic continuity, the quality and preservation of fossils and the geochemical signatures. Here we present the first results of a high-resolution carbonate C-isotope study based on the the analysis of three new research cores drilled at Cau in autumn 2015 [6]. These new data represent an important advance in the knowledge of the C-isotope record of the OAE 1a, presenting a more continuous record at a higher resolution than previous studies. This leads to the refining of the

Revisiting the Ceara Rise, equatorial Atlantic Ocean: isotope stratigraphy of ODP Leg 154 from 0 to 5 Ma

Directory of Open Access Journals (Sweden)

R. H. Wilkens

2017-07-01

Full Text Available Isotope stratigraphy has become the method of choice for investigating both past ocean temperatures and global ice volume. Lisiecki and Raymo (2005 published a stacked record of 57 globally distributed benthic δ18O records versus age (LR04 stack. In this study LR04 is compared to high-resolution records collected at all of the sites drilled during ODP Leg 154 on the Ceara Rise, in the western equatorial Atlantic Ocean. Newly developed software is used to check data splices of the Ceara Rise sites and better align out-of-splice data with in-splice data. Core images recovered from core table photos are depth and age scaled and greatly assist in the data analysis. The entire splices of ODP sites 925, 926, 927, 928 and 929 were reviewed. Most changes were minor although several were large enough to affect age models based on orbital tuning. A Ceara Rise composite record of benthic δ18O is out of sync with LR04 between 1.80 and 1.90 Ma, where LR04 exhibits two maxima but Ceara Rise data contain only one. The interval between 4.0 and 4.5 Ma in the Ceara Rise compilation is decidedly different from LR04, reflecting both the low amplitude of the signal over this interval and the limited amount of data available for the LR04 stack. A regional difference in benthic δ18O of 0.2 ‰ relative to LR04 was found. Independent tuning of Site 926 images and physical property data to the Laskar et al. (2004 orbital solution and integration of available benthic stable isotope data from the Ceara Rise provides a new regional reference section for the equatorial Atlantic covering the last 5 million years.

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

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).

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

International Nuclear Information System (INIS)

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

1990-01-01

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

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

International Nuclear Information System (INIS)

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

1993-01-01

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

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

African Journals Online (AJOL)

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

Biostratigraphy and carbon isotope stratigraphy of uppermost Cretaceous-lower Cenozoic Muzzle Group in middle Clarence valley, New Zealand

International Nuclear Information System (INIS)

Hollis, C.J.; Field, B.D.; Jones, C.M.; Strong, C.P.; Wilson, G.J.; Dickens, G.R.

2005-01-01

Muzzle Group strata exposed along southeast-flowing tributaries of the Clarence River valley, Marlborough, record hemipelagic-pelagic sedimentation across a high latitude (c. 55 degrees S), terrigenous sediment-starved, continental margin from latest Cretaceous to middle Eocene times. Studies of dinoflagellates, foraminifera, calcareous nannofossils, and radiolarians have been integrated with bulk carbonate δ 13 C profiles to establish the chronostratigraphy for two stratigraphic sections along Bluff and Muzzle Streams, middle Clarence valley. The two sections comprise similar successions. Uppermost Cretaceous (upper Haumurian) micritic limestone of Mead Hill Formation is overlain unconformably by Teredo Limestone, a c. 0.25 m thick bed of highly glauconitic, calcareous sandstone. This unit, the basal member of Amuri Limestone, is overlain conformably by c. 15 m thick Lower Limestone, micritic limestone that is glauconitic at base and progressively more marl-rich in its upper part. Lower Limestone grades up into Lower Marl, a poorly exposed, 40-70 m thick unit of alternating marl and micritic limestone beds. Biostratigraphy indicates that the base of Amuri Limestone is younger at Bluff Stream (earliest Eocene, early Waipawan) than at Muzzle Stream (late Paleocene, late Teurian). In the condensed (12 m) upper Paleocene-lower Eocene Amuri Limestone sequence at Muzzle Stream, a trend in δ 13 C from high (≥2.4 permille) to low (≤1 permille) values is consistent with global records across three major climate or carbon cycle perturbations: the late Paleocene carbon isotope maximum (PCIM, 59-56 Ma), the initial Eocene thermal maximum (IETM, 55.5 Ma), and the early Eocene climatic optimum (EECO, 53-50 Ma). Probably only the upper PCIM is preserved in the 4 m thick siliceous limestone interval overlying Teredo Limestone. The IETM is well-defined by a 1 permille negative δ 13 C excursion at the base of a 0.8 m thick marl-rich unit (Dee Marl), 5 m above the base of

Correlation between high resolution sequence stratigraphy and mechanical stratigraphy for enhanced fracture characteristic prediction

Science.gov (United States)

Al Kharusi, Laiyyan M.

Sequence stratigraphy relates changes in vertical and lateral facies distribution to relative changes in sea level. These relative changes in carbonates effect early diagenesis, types of pores, cementation and dissolution patterns. As a result, in carbonates, relative changes in sea level significantly impact the lithology, porosity, diagenesis, bed and bounding surfaces which are all factors that control fracture patterns. This study explores these relationships by integrating stratigraphy with fracture analysis and petrophysical properties. A special focus is given to the relationship between mechanical boundaries and sequence stratigraphic boundaries in three different settings: (1) Mississippian strata in Sheep Mountain Anticline, Wyoming, (2) Mississippian limestones in St. Louis, Missouri, and (3) Pennsylvanian limestones intermixed with elastics in the Paradox Basin, Utah. The analysis of these sections demonstrate that a fracture hierarchy exists in relation to the sequence stratigraphic hierarchy. The majority of fractures (80%) terminate at genetic unit boundaries or the internal flooding surface that separates the transgressive from regressive hemicycle. Fractures (20%) that do not terminate at genetic unit boundaries or their internal flooding surface terminate at lower order sequence stratigraphic boundaries or their internal flooding surfaces. Secondly, the fracture spacing relates well to bed thickness in mechanical units no greater than 0.5m in thickness but with increasing bed thickness a scatter from the linear trend is observed. In the Paradox Basin the influence of strain on fracture density is illustrated by two sections measured in different strain regimes. The folded strata at Raplee Anticline has higher fracture densities than the flat-lying beds at the Honaker Trail. Cemented low porosity rocks in the Paradox Basin do not show a correlation between fracture pattern and porosity. However velocity and rock stiffness moduli's display a slight

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

International Nuclear Information System (INIS)

Ishida, T.

1975-01-01

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

High resolution sequence stratigraphy in China

International Nuclear Information System (INIS)

Zhang Shangfeng; Zhang Changmin; Yin Yanshi; Yin Taiju

2008-01-01

Since high resolution sequence stratigraphy was introduced into China by DENG Hong-wen in 1995, it has been experienced two development stages in China which are the beginning stage of theory research and development of theory research and application, and the stage of theoretical maturity and widely application that is going into. It is proved by practices that high resolution sequence stratigraphy plays more and more important roles in the exploration and development of oil and gas in Chinese continental oil-bearing basin and the research field spreads to the exploration of coal mine, uranium mine and other strata deposits. However, the theory of high resolution sequence stratigraphy still has some shortages, it should be improved in many aspects. The authors point out that high resolution sequence stratigraphy should be characterized quantitatively and modelized by computer techniques. (authors)

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.

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

Science.gov (United States)

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

2014-09-01

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

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

Science.gov (United States)

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

2010-12-01

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

Strontium isotopes in carbonate deposits at Crater Flat, Nevada

International Nuclear Information System (INIS)

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

1991-01-01

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

Strontium isotopes in carbonate deposits at Crater Flat, Nevada

International Nuclear Information System (INIS)

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

1991-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

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

International Nuclear Information System (INIS)

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

2006-01-01

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

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

International Nuclear Information System (INIS)

Atekwana, Eliot A.; Seeger, Eric J.

2015-01-01

The major ionic and dissolved inorganic carbon (DIC) concentrations and the stable carbon isotope composition of DIC (δ"1"3C_D_I_C) were measured in a freshwater aquifer contaminated by produced water brine with petroleum hydrocarbons. Our aim was to determine the effects of produced water brine contamination on the carbonate evolution of groundwater. The groundwater was characterized by three distinct anion facies: HCO_3"−-rich, SO_4"2"−-rich and Cl"−-rich. The HCO_3"−-rich groundwater is undergoing closed system carbonate evolution from soil CO_2_(_g_) and weathering of aquifer carbonates. The SO_4"2"−-rich groundwater evolves from gypsum induced dedolomitization and pyrite oxidation. The Cl"−-rich groundwater is contaminated by produced water brine and undergoes common ion induced carbonate precipitation. The δ"1"3C_D_I_C of the HCO_3"−-rich groundwater was controlled by nearly equal contribution of carbon from soil CO_2_(_g_) and the aquifer carbonates, such that the δ"1"3C of carbon added to the groundwater was −11.6‰. In the SO_4"2"−-rich groundwater, gypsum induced dedolomitization increased the "1"3C such that the δ"1"3C of carbon added to the groundwater was −9.4‰. In the produced water brine contaminated Cl"−-rich groundwater, common ion induced precipitation of calcite depleted the "1"3C such that the δ"1"3C of carbon added to the groundwater was −12.7‰. The results of this study demonstrate that produced water brine contamination of fresh groundwater in carbonate aquifers alters the carbonate and carbon isotopic evolution. - Highlights: • We studied carbonate and δ"1"3C evolution in groundwater contaminated by produced water brine. • Multiple processes affect the carbonate and δ"1"3C evolution of the groundwater. • The processes are carbonate weathering, dedolomitization and common ion induce calcite precipitation. • The δ"1"3C added to DIC was −11.6‰ for weathering, −9.4‰ for dedolomitization

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

Science.gov (United States)

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

2018-04-01

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

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

Czech Academy of Sciences Publication Activity Database

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

2015-01-01

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

Variability in carbon isotope fractionation of trichloroethene during degradation by persulfate activated with zero-valent iron: Effects of inorganic anions

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-01

Stable carbon isotope analysis has the potential to be used for assessing the performance of in situ remediation of organic contaminants. Successful application of this isotope technique requires understanding the magnitude and variability in carbon isotope fractionation associated with the reactions under consideration. This study investigated the influence of inorganic anions (sulfate, bicarbonate, and chloride) on carbon isotope fractionation of trichloroethene (TCE) during its degradation by persulfate activated with zero-valent iron. The results demonstrated that the significant carbon isotope fractionation (enrichment factors ε ranging from − 3.4 ± 0.3 to − 4.3 ± 0.3 ‰) was independent on the zero-iron dosage, sulfate concentration, and bicarbonate concentration. However, the ε values (ranging from − 7.0 ± 0.4 to − 13.6 ± 1.2 ‰) were dependent on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during TCE degradation by persulfate activated with zero-valent iron. The dependence of ε values on chloride concentration, indicated that TCE degradation mechanisms may be different from the degradation mechanism caused by sulfate radical (SO{sub 4}·{sup −}). Ignoring the effect of chloride on ε value may cause numerous uncertainties in quantitative assessment of the performance of the in situ chemical oxidation (ISCO). - Highlights: • Significant C isotope fractionation for TCE degradation by Fe{sup 0} activated persulfate. • The enrichment factors was independent of Fe{sup 0}, SO{sub 4}{sup 2−}, or HCO{sub 3}{sup −} concentration. • Cl{sup −} significantly influenced the carbon isotope fractionation.

Variability in carbon isotope fractionation of trichloroethene during degradation by persulfate activated with zero-valent iron: Effects of inorganic anions

International Nuclear Information System (INIS)

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

2016-01-01

Stable carbon isotope analysis has the potential to be used for assessing the performance of in situ remediation of organic contaminants. Successful application of this isotope technique requires understanding the magnitude and variability in carbon isotope fractionation associated with the reactions under consideration. This study investigated the influence of inorganic anions (sulfate, bicarbonate, and chloride) on carbon isotope fractionation of trichloroethene (TCE) during its degradation by persulfate activated with zero-valent iron. The results demonstrated that the significant carbon isotope fractionation (enrichment factors ε ranging from − 3.4 ± 0.3 to − 4.3 ± 0.3 ‰) was independent on the zero-iron dosage, sulfate concentration, and bicarbonate concentration. However, the ε values (ranging from − 7.0 ± 0.4 to − 13.6 ± 1.2 ‰) were dependent on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during TCE degradation by persulfate activated with zero-valent iron. The dependence of ε values on chloride concentration, indicated that TCE degradation mechanisms may be different from the degradation mechanism caused by sulfate radical (SO_4·"−). Ignoring the effect of chloride on ε value may cause numerous uncertainties in quantitative assessment of the performance of the in situ chemical oxidation (ISCO). - Highlights: • Significant C isotope fractionation for TCE degradation by Fe"0 activated persulfate. • The enrichment factors was independent of Fe"0, SO_4"2"−, or HCO_3"− concentration. • Cl"− significantly influenced the carbon isotope fractionation.

Measurements of flux and isotopic composition of soil carbon dioxide

International Nuclear Information System (INIS)

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

2002-01-01

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

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

International Nuclear Information System (INIS)

Grossmann, E.L.

1984-01-01

Carbon and oxygen isotopic analyses have been performed on live-stained aragonitic and calcitic benthic foraminifera and dissolved inorganic carbon from the Southern California Borderland to examine carbon isotopic fractionation in foraminifera. Temperature, salinity and pH data have also been collected to permit accurate determination of the delta 13 C of bicarbonate ion and thus aragonite-HCO 3 - and calcite-HCO 3 - isotopic enrichment factors (epsilonsub(ar-b) and epsilonsub(cl-b), respectively). Only species which precipitate in 18 O equilibrium have been considered. epsilonsub (ar-b) values based on Hoeglundina elegans range from 1.9 per mille at 2.7 deg C to 1.1 per mille at 9.5 deg C. The temperature dependence of epsilonsub(ar-b) is considerably greater than the equilibrium equation would predict and may be due to a vital effect. The calcitic foraminifera Cassidulina tortuosa, Cassidulina braziliensis, and Cassidulina limbata, Bank and Terrace dwellers, have similar delta 13 C values and yield an average epsilonsub(cl-b) value of -0.2 +- 0.1 per mille between 8 deg and 10 deg C. Calcitic Uvigerina curticosta, Uvigerina peregrina, and megalospheric B, argentea, Slope and Basin dwellers, are -0.7 +- 0.1 per mille enriched relative to ambient bicarbonate for 3 to 9 deg C. (author)

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

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

International Nuclear Information System (INIS)

Deitz, V.R.

1985-01-01

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

Fractionation of carbon isotopes by thermophilic methanogenic bacteria

International Nuclear Information System (INIS)

Ivanov, M.V.; Belyaev, S.S.; Zyakun, A.M.; Bondar, V.A.; Shipin, O.P.; Laurinavichus, K.S.

1985-01-01

The authors investigated the pattern of fractionation of stable carbon isotopes by the thermophilic methane-forming bacteria under different growth conditions and at various rates of formation of methane. A pure culture of Methanobacterium thermoautotrophicum was used in the experiments under the following growth conditions: temperature 65-70 0 C; pH 7.2-7.6; NaCl content 0-0.9 g/liter. The methanogenic bacteria were cultivated in 0.15 liter flasks in mineral medium. A mixture of CO 2 and H 2 in a 1:4 ratio by volume served as the sole carbon and energy source. In all experiments, not more than 5% of the initial CO 2 level was utilized. The rate of methane generation was altered by adjusting the physicochemical growth parameters (temperature from 45-70 0 C, salinity from 0.9 to 40 g/liter NaCl, pH from 6.3 to 7.2). Methane in the samples was quantitatively determined in a chromatograph which had a flame-ionization detector and a column containing Porapak Q sorbent at T = 120 0 C. The carrier gas was CO 2 . The average specific rate of methane formation was calculated as ml CH 4 per mg dry biomass of bacteria per h. Soluble mineral carbon was isolated form the acidified culture liquid in the form of CO 2 and was quantitatively determined in a Chrom-4 chromatography provided with a katharometer and a column containing activated charcoal at T = 150 0 . The gas carrier was helium. The isotopic composition of carbon was determined in a CH-7 mass-spectrometer and was expressed in 13 C values (per thousand) with respect to the international PDB standard

Rates of carbonate soil evolution from carbon, U- and Th-series isotope studies: Example of the Astian sands (SE France)

Science.gov (United States)

Barbecot, Florent; Ghaleb, Bassam; Hillaire-Marcel, Claude

2015-04-01

In carbonate rich soils, C-isotopes (14C, 13C) and carbonate mass budget may inform on centennial to millennial time scale dissolution/precipitation processes and weathering rates, whereas disequilibria between in the U- and Th-decay series provide tools to document high- (228Ra-228Th-210Pb) to low- (234U, 230Th, 231Pa, 226Ra) geochemical processes rate, covering annual to ~ 1Ma time scales, governing both carbonate and silicate soil fractions. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in soils developed over Astian sands formation (up to ~ 30% carbonate) from the Béziers area (SE France). A >20 m thick unsaturated zone was sampled firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes and 14C-measurements, were complemented with 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements. Whereas the upper 7 m depict geochemical and isotopic features forced by dissolution/precipitation processes leading to variable radioactive disequilibria, but overall deficits in more soluble elements of the decay series, the lower part of the sequence shows strong excesses in 234U and 230Th over parent isotopes (i.e., 238U and 234U, respectively). These features might have been interpreted as the result of successive phases of U-loss and gains. However, 226Ra and 230Th are in near-equilibrium, thus leading to conclude at a more likely slow enrichment process in both 234Th(234U) and 230Th, which we link to dissolved U-decay during groundwater recharge events. In addition, 210Pb deficits (vs parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to gaseous 222Rn-diffusion over the cliff outcrop. Based on C-isotope and chemical analysis, reaction rates at 14C-time scale are distinct from those estimates at the short- or long-lived U-series isotopes

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

Determination of carbon isotope ratios in plant starch via selective enzymatic hydrolysis

International Nuclear Information System (INIS)

Schimmelmann, A.; DeNiro, M.J.

1983-01-01

A method for the determination of the carbon isotope ratios in bipolymers hydrolyzed by enzymatic action consists of separating the monomer by passage through a dialysis membrane and then combusting the monomer prior to isotopic analysis. The method is described for application to the analysis of starch, but it should find application for polymers than can be degraded quantitatively to monomers and/or oligomers using specific hydrolytic enzymes

Differential utilization of allochthonous and autochthonous carbon by aquatic insects of two shrub-steppe desert spring-streams: A stable carbon isotope analysis and critique of the method

Energy Technology Data Exchange (ETDEWEB)

Mize, A. L. [Old Dominion Univ., Norfolk, VA (United States)

1993-06-01

The purpose of this study is to assess whether the carbon supporting stream food webs comes principally from terrestrial sources or is produced within the stream. Lacking data to resolve the allochthonous/autochthonous issue with any finality, stream ecologists have alternately postulated that stream carbon was principally autochthonous or principally allochthonous. Others argued that autochthonous and allochthonous carbon resources cannot be separated and that the allochthonous/autochthonous dependence issue is unresolvable. Many investigators have seized upon stable carbon isotopes technology as the tool to resolve the controversy. Unfortunately most investigators have conceded that the results are rarely quantitative and that the qualitative relationships are ambiguous. This study points out the fallacies of trying to conjure single isotopic values for either allochthonous or autochthonous carbon. It suggests that stable carbon isotope technology is not reliable in establishing specific consumer/food source relations and that it is not suitable for assessing allochthonous/autochthonous carbon dependence in freshwater streams.

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

Automated determination of the stable carbon isotopic composition (δ13C) of total dissolved inorganic carbon (DIC) and total nonpurgeable dissolved organic carbon (DOC) in aqueous samples: RSIL lab codes 1851 and 1852

Science.gov (United States)

Révész, Kinga M.; Doctor, Daniel H.

2014-01-01

The purposes of the Reston Stable Isotope Laboratory (RSIL) lab codes 1851 and 1852 are to determine the total carbon mass and the ratio of the stable isotopes of carbon (δ13C) for total dissolved inorganic carbon (DIC, lab code 1851) and total nonpurgeable dissolved organic carbon (DOC, lab code 1852) in aqueous samples. The analysis procedure is automated according to a method that utilizes a total carbon analyzer as a peripheral sample preparation device for analysis of carbon dioxide (CO2) gas by a continuous-flow isotope ratio mass spectrometer (CF-IRMS). The carbon analyzer produces CO2 and determines the carbon mass in parts per million (ppm) of DIC and DOC in each sample separately, and the CF-IRMS determines the carbon isotope ratio of the produced CO2. This configuration provides a fully automated analysis of total carbon mass and δ13C with no operator intervention, additional sample preparation, or other manual analysis. To determine the DIC, the carbon analyzer transfers a specified sample volume to a heated (70 °C) reaction vessel with a preprogrammed volume of 10% phosphoric acid (H3PO4), which allows the carbonate and bicarbonate species in the sample to dissociate to CO2. The CO2 from the reacted sample is subsequently purged with a flow of helium gas that sweeps the CO2 through an infrared CO2 detector and quantifies the CO2. The CO2 is then carried through a high-temperature (650 °C) scrubber reactor, a series of water traps, and ultimately to the inlet of the mass spectrometer. For the analysis of total dissolved organic carbon, the carbon analyzer performs a second step on the sample in the heated reaction vessel during which a preprogrammed volume of sodium persulfate (Na2S2O8) is added, and the hydroxyl radicals oxidize the organics to CO2. Samples containing 2 ppm to 30,000 ppm of carbon are analyzed. The precision of the carbon isotope analysis is within 0.3 per mill for DIC, and within 0.5 per mill for DOC.

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

Science.gov (United States)

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

2017-12-01

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

Synchronisation of palaeoenvironmental records over the last 60,000 years, and an extended INTIMATE event stratigraphy to 48,000 b2k

DEFF Research Database (Denmark)

Blockley, S.P.E.; Lane, C.S.; Hardiman, M.

2012-01-01

study period back to 60,000 years. As a first step, the INTIMATE event stratigraphy has now been extended to include 8000-48,000 b2k based on a combined NGRIP and GRIP isotope profile against a GICC05 chronology and key tephra horizons from Iceland and continental European volcanic sources. In this lead...

Assessment of primary production in a eutrophic lake from carbon and nitrogen isotope ratios of a carnivorous fish

International Nuclear Information System (INIS)

Yoshioka, Takahito

1991-01-01

The carbon and nitrogen isotope ratios of Hypomesus transpacificus (a pond smelt) in a eutrophic lake, Lake Suwa, were measured from April to September in 1986 and 1987. The differences in the isotope ratios between these two years were observed. The stable isotopes were transferred from phytoplankton to zooplankton and pond smelt, associated with organic matters. Therefore, the difference in the isotope ratios in two years seemed to reflect the differences of the proceeding of primary production. It was suggested that the carbon and nitrogen isotope ratios of animal, whose trophic level is far from primary producer, can be the qualitative indicators for assessing the primary production in a lake ecosystem. (author)

Stable isotope (δ"1"3C and δ"1"5N) based interpretation of organic matter source and paleoenvironmental conditions in Al-Azraq basin, Jordan

International Nuclear Information System (INIS)

Ahmad, Khaldoun; Davies, Caroline

2017-01-01

This study examines the stable isotopes of carbon and nitrogen from cored lacustrine sediments of the Al-Azraq, an arid lake basin on the Jordan Plateau. Lacustrine sediments contain valuable records of paleoenvironmental conditions, recording local and regional responses to environmental change. Previous paleo-reconstructions on the Jordan Plateau are based on archaeology, pollen, mineralogy, and stratigraphy. The application of organic geochemistry analyses to these lake sediments identifies multiple sources of organic matter, biological production, and contributes to understanding the paleoenvironments of the Al-Azraq basin during the mid-Pleistocene period. Organic carbon concentration (Corg) provides an overview of the organic matter distribution. Carbon isotopic composition (δ13Corg) and nitrogen isotopic composition (δ15N) are indicators of organic matter sources and paleoproductivity. Magnetic susceptibility (MGSUS) measured the concentration of ferromagnetic minerals and indicated aeolian inputs. Organic geochemistry differentiated five paleoenvironmental zones with specific sources of organic matter, both aquatic and terrestrial. It identified a long period of climate wetter than the present, punctuated by a short intense period of aridity. Diagenesis plays an important role in the decomposition of organic matter and studies indicate this degradation can alter the isotopic signals of organic matter. Analyses of the isotopic signals and statistical analyses demonstrate diagenesis is not a factor in the Al-Azraq sediments in all but Zone 4 of the paleoenvironmental zones. This Zone is defined by less negative carbon isotopic composition and the presence of thick primary gypsum layers, in addition to the influx of high peaks of aeolian sediment as reflected in the magnetic susceptibility data. Stable isotope geochemistry provides detailed information on the paleoenvironments of lake sediments, and is applicable to typically challenging arid basin sediments

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

DEFF Research Database (Denmark)

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

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...... food in the diet was estimated at 21% from the mean δ(13) C value, 25% from the mean δ(15) N value, and 23% from the FFQ. CONCLUSION: Nail samples for analysis of stable isotopes of carbon and nitrogen were convenient to collect during a large population health survey among the Inuit. Isotope...

The stratigraphy of Mars

Science.gov (United States)

Tanaka, Kenneth L.

1986-01-01

A global stratigraphy of Mars was developed from a global geologic map series derived from Viking images; the stratigraphy is composed of three maps. A new chronostratigraphic classification system which consists of lower, middle, and upper Noachian, Hesperian, and Amazonian systems is described. The crater-density boundaries of the chronostratigraphic units and the absolute ages of the Martian epochs aer estimated. The relative ages of major geologic units and featues are calculated and analyzed. The geologic history of Mars is summarized on the maps in terms of epochs.

Tests of intestinal absorption using carbon-14-labeled isotopes

International Nuclear Information System (INIS)

Fromm, H.; Sarva, R.P.

1983-01-01

Beta radiation-emitting isotopes are being used increasingly in diagnostic gastroenterology for the study of absorption. The major reason for the popularity of radioisotopes is that their use is convenient for patient and physician alike. They often obviate naso- or orointestinal intubation and the collection, storage, and analysis of stool. The radioactivity used for the studies of digestive and absorptive processes is small and is not hazardous. In spite of the safety of the radiolabeled compounds, their use is restricted in children and pregnant women. Therefore, for most tests, promising alternative methods that make use of the stable isotope of carbon, /sup 13/C, instead of the radioactive /sup 14/C have been developed. The analysis of stable isotopes requires more sophisticated technology than that of radioactive compounds, however. Only a few centers presently are equipped and staffed to analyze stable isotopes on a routine basis. In contrast, the analysis of radioactive isotopes has become a routine procedure in almost ever major laboratory. The last decade has brought the development of several radioactive absorption tests. The clinically most useful tests relate to the study of bile acid, fat, lactose, and xylose absorption. All of these tests utilize the excretion rate of /sup 14/CO/sub 2/ in breath after ingestion of a /sup 14/C-labeled compound as a measure of the rate of its absorption or malabsorption

The application of carbon isotope discrimination of charred wheat grains to reconstruct Late Holocene climate change and identify water management strategy in northwest China

Science.gov (United States)

Wang, W.; An, C.; Duan, F.; Zhao, Y.; Cao, Z.

2017-12-01

The AMS 14C dating and corresponding carbon stable isotope datum of charred wheat grains from archaeological sites in northwest China especially Hexi Corridor and Xinjiang have been collected widely to study its potential roles in reconstructing past climate change and identifying water management strategies through comparison with integrated regional humidity index, carbon isotope data of wheat grown under modern irrigation environment from study area and Mediterranean charred wheat carbon isotope data. The results suggest (1) carbon isotope discrimination values of charred wheat both in Hexi corridor and Xinjiang could respond well to regional moisture change, and there are also good positive correlation relationship between them (2) in contrast to consistent relationship between decreased carbon isotope discrimination values of charred wheat and dry climate condition, increased carbon isotope discrimination values does not represent wetter regional climate completely and may also reveal effects of human irrigation activities. The higher carbon isotope discrimination value of charred wheat which occurred in the Hexi Corridor from 4000 to 3850 a BP, 2100 a BP and 550 a BP and in Tianshan area of Xinjiang from 3730 a BP could be likely to be related with human activities (3) the carbon isotope discrimination value of charred wheat may have a certain limit which is generally not beyond 19‰. And this upper limit could influence its availability in reflecting abrupt change of precipitation/humidity especially rapid wetter trend. We conclude that carbon isotope analysis of charred wheat grains could be a good tool for reconstructing past climate change and identifying ancient irrigation practices.

A study on the isotope effects in the reduction of carbon dioxide by zinc

International Nuclear Information System (INIS)

Senegacnik, M.

1957-06-01

We have determined the isotope effects which occur in the reduction of carbon dioxide by zinc. It has been shown that in the case of irreversible surface reactions, Bernstein's equation which permits the calculation of the fractionation factor is still valid. These experimental factors are in good agreement with those obtained by calculating the partition functions of the adsorbed activated complexes. In the reaction mechanism used, the model of the activated complex corresponds to the dissociation of one of the carbon oxygen bonds CO 2 → CO + O. Perturbations arising from the slight reversibility of the reaction Zn + CO 2 ↔ ZnO + CO on the isotope effects on the carbon and oxygen atoms have also been calculated. (author) [fr

Simulation of carbon isotope discrimination of the terrestrial biosphere

Science.gov (United States)

Suits, N. S.; Denning, A. S.; Berry, J. A.; Still, C. J.; Kaduk, J.; Miller, J. B.; Baker, I. T.

2005-03-01

We introduce a multistage model of carbon isotope discrimination during C3 photosynthesis and global maps of C3/C4 plant ratios to an ecophysiological model of the terrestrial biosphere (SiB2) in order to predict the carbon isotope ratios of terrestrial plant carbon globally at a 1° resolution. The model is driven by observed meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), constrained by satellite-derived Normalized Difference Vegetation Index (NDVI) and run for the years 1983-1993. Modeled mean annual C3 discrimination during this period is 19.2‰; total mean annual discrimination by the terrestrial biosphere (C3 and C4 plants) is 15.9‰. We test simulation results in three ways. First, we compare the modeled response of C3 discrimination to changes in physiological stress, including daily variations in vapor pressure deficit (vpd) and monthly variations in precipitation, to observed changes in discrimination inferred from Keeling plot intercepts. Second, we compare mean δ13C ratios from selected biomes (Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal) to the observed values from Keeling plots at these biomes. Third, we compare simulated zonal δ13C ratios in the Northern Hemisphere (20°N to 60°N) to values predicted from high-frequency variations in measured atmospheric CO2 and δ13C from terrestrially dominated sites within the NOAA-Globalview flask network. The modeled response to changes in vapor pressure deficit compares favorably to observations. Simulated discrimination in tropical forests of the Amazon basin is less sensitive to changes in monthly precipitation than is suggested by some observations. Mean model δ13C ratios for Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal biomes compare well with the few measurements available; however, there is more variability in observations than in the simulation, and modeled δ13C values for tropical forests are heavy relative to observations

Factors controlling shell carbon isotopic composition of land snail Acusta despecta sieboldiana estimated from lab culturing experiment

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Zhang, N.; Yamada, K.; Suzuki, N.; Yoshida, N.

2014-05-01

The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail species, Acusta despecta sieboldiana collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on previous works and on results obtained in this study, a simple but credible framework is presented for discussion of how each source and environmental parameter can affect shell carbonate δ13C values. According to this framework and some reasonable assumptions, we have estimated the contributions of different carbon sources for each snail individual: for cabbage (C3 plant) fed groups, the contributions of diet, atmospheric CO2 and ingested limestone respectively vary as 66-80%, 16-24%, and 0-13%. For corn (C4 plant) fed groups, because of the possible food stress (lower consumption ability of C4 plant), the values vary respectively as 56-64%, 18-20%, and 16-26%. Moreover, we present new evidence that snails have discrimination to choose C3 and C4 plants as food. Therefore, we suggest that food preferences must be considered adequately when applying δ13C in paleo-environment studies. Finally, we inferred that, during egg laying and hatching of our cultured snails, carbon isotope fractionation is controlled only by the isotopic exchange of the calcite-HCO3--aragonite equilibrium.

Factors controlling shell carbon isotopic composition of land snail Acusta despecta sieboldiana estimated from laboratory culturing experiment

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Zhang, N.; Yamada, K.; Suzuki, N.; Yoshida, N.

2014-10-01

The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail subspecies, Acusta despecta sieboldiana, collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on results obtained from previous works and this study, a simple but credible framework is presented to illustrate how each source and environmental parameter affects shell carbonate δ13C values. According to this framework and some reasonable assumptions, we estimated the contributions of different carbon sources for each snail individual: for cabbage-fed (C3 plant) groups, the contributions of diet, atmospheric CO2, and ingested limestone vary in the ranges of 66-80, 16-24, and 0-13%, respectively. For corn-fed (C4 plant) groups, because of the possible food stress (less ability to consume C4 plants), the values vary in the ranges of 56-64, 18-20, and 16-26%, respectively. Moreover, according to the literature and our observations, the subspecies we cultured in this study show preferences towards different plant species for food. Therefore, we suggest that the potential food preference should be considered adequately for some species in paleoenvironment studies. Finally, we inferred that only the isotopic exchange of the calcite-HCO3--aragonite equilibrium during egg laying and hatching of our cultured snails controls carbon isotope fractionation.

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

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

2015-12-01

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

Ion beam trajectory simulation of carbon isotopes in cyclotron DECY-13

International Nuclear Information System (INIS)

Pramudita Anggraita

2014-01-01

A simulation on the ion beam trajectories of various carbon isotopes "1"2C, "1"3C, and "1"4C in DECY-13 cyclotron has been carried out using Scilab 5.4.1 software. Calculations in the simulation were carried out in 3 dimensions. The simulation shows trajectory separations, which provide possibility for "1"4C measurement such as in carbon dating at accelerating voltage frequency of about 72 MHz. (author)

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope and Water Chemistry Characterizations

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Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike; Bissada, Adry K.

2013-01-01

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41 deg 32'N, 120 deg 5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4(2-), respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth

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

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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.

Carbon Monoxide Stable Isotopes: Extraction Technique Development and Urban Atmospheric Analysis

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Vimont, Isaac Josef

We have developed an extraction system to analyze isotopes of carbon monoxide (CO). We then analyzed CO isotopes for two years at Indianapolis, IN, USA. These measurements were done at three towers, one of which measured incoming, background air into the city. We quantitatively removed the background signal and determined the urban CO mole fraction and isotopic enhancements. During the winter months, we constrained the isotopic signature and concluded that the majority of CO produced during the winter was produced by fossil fuel combustion. We found that the Indianapolis fossil fuel signature differed from that of studies done in Europe. Further, we performed a limited traffic study to look at CO isotopes from traffic. While this was not conclusive, it did support our hypothesis that a larger fraction of the Indianapolis vehicle fleet may have malfunctioning catalytic systems, which biases the isotopic results, particularly for delta18O. We used the wintertime fossil fuel isotopic signature to help constrain the summertime budget. It was hypothesized that a second source of CO was significant during the summer months. Oxidation of biogenically produced volatile organic compounds (BVOC's) was one possible source. Oxidized BVOC's were consistent with the changes between our winter and summer isotopic source signatures. We then used the isotopic signatures to determine that between zero and sixty percent of the summertime CO budget was produced from oxidized VOC's. This provided the first direct evidence of a larger percentage of urban CO being produced by oxidized VOC's.

Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

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Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

2017-12-08

sequence stratigraphic cycles that compose the Eocene to Miocene Oldsmar, Avon Park, and Arcadia Formations. The mapping of these seismic-reflection and well data has produced a refined Cenozoic sequence stratigraphic, seismic stratigraphic, and hydrogeologic framework of southeastern Florida. The upward transition from the Oldsmar Formation to the Avon Park Formation and the Arcadia Formation embodies the evolution from (1) a tropical to subtropical, shallow-marine, carbonate platform, represented by the Oldsmar and Avon Park Formations, to (2) a broad, temperate, mixed carbonate-siliciclastic shallow marine shelf, represented by the lower part of the Arcadia Formation, and to (3) a temperate, distally steepened carbonate ramp represented by the upper part of the Arcadia Formation.In the study area, the depositional sequences and seismic sequences have a direct correlation with hydrogeologic units. The approximate upper boundary of four principal permeable units of the Floridan aquifer system (Upper Floridan aquifer, Avon Park permeable zone, uppermost major permeable zone of the Lower Floridan aquifer, and Boulder Zone) have sequence stratigraphic and seismic-reflection signatures that were identified on cross sections, mapped, or both, and therefore the sequence stratigraphy and seismic stratigraphy were used to guide the development of a refined spatial representation of these hydrogeologic units. In all cases, the permeability of the four permeable units is related to stratiform megaporosity generated by ancient dissolution of carbonate rock associated with subaerial exposure and unconformities at the upper surfaces of carbonate depositional cycles of several hierarchical scales ranging from high-frequency cycles to depositional sequences. Additionally, interparticle porosity also contributes substantially to the stratiform permeability in much of the Upper Floridan aquifer. Information from seismic stratigraphy allowed 3D geomodeling of hydrogeologic units�

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

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

2016-04-01

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

Assessment of Bacterial Degradation of Aromatic Hydrocarbons in the Environment by Analysis of Stable Carbon Isotope Fractionation

International Nuclear Information System (INIS)

Meckenstock, Rainer U.; Morasch, Barbara; Kaestner, Matthias; Vieth, Andrea; Richnow, Hans Hermann

2002-01-01

13 C/ 12 C stable carbon isotope fractionation was used to assess biodegradation in contaminated aquifers with toluene as a model compound. Different strains of anaerobic bacteria (Thauera aromatica, Geobacter metallireducens, and the sulfate-reducing strain TRM1) showed consistent 13 C/ 12 C carbon isotope fractionation with fractionation factors between αC = 1.0017 and 1.0018. In contrast, three cultures of aerobic organisms, using different mono- and dioxygenase enzyme systems to initiate toluene degradation, showed variable isotope fractionation factors of αC = 1.0027 (Pseudomonasputida strain mt-2), αC = 1.0011 (Ralstonia picketii), andαC = 1.0004 (Pseudomonas putida strain F1). The great variability of isotope fractionation between different aerobic bacterial strains suggests that interpretation of isotope data in oxic habitats can only be qualitative. A soil column was run as a model system for contaminated aquifers with toluene as the carbon source and sulfate as the electron acceptor and samples were taken at different ports along the column. Microbial toluene degradation was calculated based on the 13 C/ 12 C isotope fractionation factors of the batch culture experiments together with the observed 13 C/ 12 C isotope shifts of the residual toluene fractions. The calculated percentage of biodegradation, B, correlated well with the decreasing toluene concentrations at the sampling ports and indicated the increasing extent of biodegradation along the column. The theoretical toluene concentrations as calculated based on the isotope values matched the measured concentrations at the different sampling ports indicating that the Rayleigh equation can be used to calculate biodegradation in quasi closed systems based on measured isotope shifts. A similar attempt was performed to assess toluene degradation in a contaminated, anoxic aquifer. A transect of groundwater wells was monitored along the main direction of the groundwater flow and revealed decreasing

Stable carbon isotopes as an indicator for soil degradation in an alpine environment (Urseren Valley, Switzerland).

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Schaub, Monika; Alewell, Christine

2009-05-01

Analyses of soil organic carbon (SOC) content and stable carbon isotope signatures (delta(13)C) of soils were assessed for their suitability to detect early stage soil erosion. 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 visible 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 delta(13)C and carbon content (r > 0.80) is found for upland soils not affected by soil erosion, indicating that depth profiles of delta(13)C of these upland soils mainly reflect decomposition of SOC. Long-term disturbance of an upland soil is indicated by decreasing correlation of delta(13)C and SOC (r soil erosion in hill slope transects from uplands to adjacent wetlands is documented as an intermediate delta(13)C value (-27.5 per thousand) for affected wetland soil horizons (0-12 cm) between upland (aerobic metabolism, relatively heavier delta(13)C of -26.6 per thousand) and wetland isotopic signatures (anaerobic metabolism, relatively lighter delta(13)C of -28.6 per thousand). Carbon isotopic signature and SOC content are found to be sensitive indicators of short- and long-term soil erosion processes. Copyright (c) 2009 John Wiley & Sons, Ltd.

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

International Nuclear Information System (INIS)

Pichlmayer, F.

1986-06-01

For carbon isotope investigations with a moderate precision demand of about 0.2 per mil in the isotope ratio fast and reliable results are attained by on line combination of the ANA 1500 Elemental Analyzer and the MAT 251 Isotope Mass Spectrometer. The crucial point hereof is the gas splitting device. By proper design and adjustment of the analytical parameters, good sample efficiency and a sharp CO 2 bulk within the He stream is reached. The main characteristics of this combined equipment are described and some isotopic results of organic and anorganic carbon in lake sediment-samples are given as well as deltasup1 3 C-analyses of spiritous liquors. (Author)

Environmental isotope hydrology

International Nuclear Information System (INIS)

1973-01-01

Environmental isotope hydrology is a relatively new field of investigation based on isotopic variations observed in natural waters. These isotopic characteristics have been established over a broad space and time scale. They cannot be controlled by man, but can be observed and interpreted to gain valuable regional information on the origin, turnover and transit time of water in the system which often cannot be obtained by other techniques. The cost of such investigations is usually relatively small in comparison with the cost of classical hydrological studies. The main environmental isotopes of hydrological interest are the stable isotopes deuterium (hydrogen-2), carbon-13, oxygen-18, and the radioactive isotopes tritium (hydrogen-3) and carbon-14. Isotopes of hydrogen and oxygen are ideal geochemical tracers of water because their concentrations are usually not subject to change by interaction with the aquifer material. On the other hand, carbon compounds in groundwater may interact with the aquifer material, complicating the interpretation of carbon-14 data. A few other environmental isotopes such as 32 Si and 238 U/ 234 U have been proposed recently for hydrological purposes but their use has been quite limited until now and they will not be discussed here. (author)

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

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

2012-12-01

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

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

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

2017-04-01

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

A free-air system for long-term stable carbon isotope labeling of adult forest trees

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Stable carbon (C) isotopes, in particular employed in labeling experiments, are an ideal tool to broaden our understanding of C dynamics in trees and forest ecosystems. Here, we present a free-air exposure system, named isoFACE, designed for long-term stable C isotope labeling in...

Some carbonates from Lagoa Real uranium province, State of Bahia: studies on fluid inclusion and stable isotope

International Nuclear Information System (INIS)

Fuzikawa, K.

1982-01-01

The geochemical conditions of the uraniferous carbonates of Lagoa Real province were studied using the fluid inclusions method and the isotopic determinations of the carbon and oxygen of these carbonates. (A.B.) [pt

Biomarkers, carbon isotopic composition and source rock potentials of Awgu coals, middle Benue trough, Nigeria

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Adedosu, Taofik A.; Sonibare, Oluwadayo O.; Tuo, Jincai; Ekundayo, Olusegun

2012-05-01

Coal and carbonaceous shale samples were collected from two boreholes (BH 94 and BH 120) in Awgu formation of Middle Benue Trough, Nigeria. Source rock potentials of the samples were studied using biomarkers and carbon isotopic composition. Biomarkers in the aliphatic fractions in the samples were studied using Gas Chromatography-Mass Spectrometry (GC-MS). The Carbon isotope analysis of individual n-alkanes in the aliphatic fraction was performed using Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometer (GC-IRMS). The abundance of hopanes, homohopanes (C31-C35), and C29 steranes in the samples indicate terrestrial plant, phytoplankton and cyanobacteria contributions to the organic matter that formed the coal. High (Pr/Ph) ratio (3.04-11.07) and isotopic distribution of individual alkanes showed that the samples consisted of mixed terrestrial/marine organic matter deposited under oxic condition in lacustrine-fluvial/deltaic depositional environment. The maturity parameters derived from biomarker distributions showed that the samples are in the main phase of oil window.

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

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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.

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

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

2010-05-01

European basins show that the climate became more humid during the Late Berriasian (Hallam et al., 1991, Schnyder et al., 2009). The aim of this project is to precisely characterize and date paleoenvironmental and paleoclimatic change during the latest Berriasian-Early Valanginian time interval in order to decipher if they can be viewed as precursor events, linked with the late Early Valanginian δ13C event. Three key sections have been studied: Capriolo (N Italy), Montclus (SE France) and Musfallen (E Switzerland) located in the Lombardian and Vocontian basins and on the Helvetic platform, respectively. Phosphorus and stable-isotope analyses have been performed, in addition to clay-mineralogy and facies determinations. The three sections show similar and comparable trends: The phosphorus content (in ppm) is higher in Late Berriasian sediments (compared to Early Berriasian and Valanginian deposits) and this period is also characterised by a decrease in δ13C values. This is interpreted as the result of enhanced continental weathering, which would be coeval with a change to a more humid climate during the Late Berriasian (Schnyder et al., 2009). References: Bornemann, A. and Mutterlose, J. (2008). "Calcareous nannofossil and d13C records from the Early Cretaceous of the Western Atlantic ocean: evidence of enhanced fertilization accross the Berriasian-Valanginian transition." palaios 23: 821-832. Duchamp-Alphonse, S., Gardin, S., Fiet, N., Bartolini, A., Blamart, D. and Pagel, M. (2007). "Fertilization of the northwestern Tethys (Vocontian basin, SE France) during the Valanginian carbon isotope perturbation: Evidence from calcareous nannofossils and trace element data." Palaeogeography, Palaeoclimatology, Palaeoecology 243(1-2): 132-151. Föllmi, K.B., Weissert, H., Bisping, M. & Funk, H. 1994: Phosphogenesis, carbon-isotope stratigraphy, and carbonate-platform evolution along the Lower Cretaceous northern tethyan margin. Geological Society of America, Bulletin 106, 729

The magnesium isotope record of cave carbonate archives

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Riechelmann, S.; Buhl, D.; Schröder-Ritzrau, A.; Riechelmann, D. F. C.; Richter, D. K.; Vonhof, H. B.; Wassenburg, J. A.; Geske, A.; Spötl, C.; Immenhauser, A.

2012-11-01

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 affecting soil zone activity and weathering balance. Several δ26Mg values of the Austrian and two

Carbon and its isotopes in mid-oceanic basaltic glasses

International Nuclear Information System (INIS)

Des Marais, D.J.

1984-01-01

Three carbon components are evident in eleven analyzed mid-oceanic basalts: carbon on sample surfaces (resembling adsorbed gases, organic matter, or other non-magmatic carbon species acquired by the glasses subsequent to their eruption), mantle carbon dioxide in vesicles, and mantle carbon dissolved in the glasses. The combustion technique employed recovered only reduced sulfur, all of which appears to be indigenous to the glasses. The dissolved carbon concentration (measured in vesicle-free glass) increases with the eruption depth of the spreading ridge, and is consistent with earlier data which show that magma carbon solubility increases with pressure. The total glass carbon content (dissolved plus vesicular carbon) may be controlled by the depth of the shallowest ridge magma chamber. Carbon isotopic fractionation accompanies magma degassing; vesicle CO 2 is about 3.8per mille enriched in 13 C, relative to dissolved carbon. Despite this fractionation, delta 13 Csub(PDB) values for all spreading ridge glasses lie within the range -5.6 and -7.5, and the delta 13 Csub(PDB) of mantle carbon likely lies between -5 and -7. The carbon abundances and delta 13 Csub(PDB) values of Kilauea East Rift glasses apparently are influences by the differentiation and movement of magma within that Hawaiian volcano. Using 3 He and carbon data for submarine hydrothermal fluids, the present-day mid-oceanic ridge mantle carbon flux is estimated very roughly to be about 1.0 x 10 13 g C/yr. Such a flux requires 8 Gyr to accumulate the earth's present crustal carbon inventory. (orig.)

Intraspecific carbon and nitrogen isotopic variability in foxtail millet (Setaria italica).

Science.gov (United States)

Lightfoot, Emma; Przelomska, Natalia; Craven, Martha; O Connell, Tamsin C; He, Lu; Hunt, Harriet V; Jones, Martin K

2016-07-15

Isotopic palaeodietary studies generally focus on bone collagen from human and/or animal remains. While plant remains are rarely analysed, it is known that plant isotope values can vary as a result of numerous factors, including soil conditions, the environment and type of plant. The millets were important food crops in prehistoric Eurasia, yet little is known about the isotopic differences within millet species. Here we compare the stable isotope ratios within and between Setaria italica plants grown in a controlled environment chamber. Using homogenised samples, we compare carbon isotope ratios of leaves and grains, and nitrogen isotope ratios of grains, from 29 accessions of Setaria italica. We find significant isotopic variability within single leaves and panicles, and between leaves and panicles within the same plant, which must be considered when undertaking plant isotope studies. We find that the leaves and grains from the different accessions have a ca 2‰ range in δ(13) C values, while the nitrogen isotope values in the grains have a ca 6‰ range. We also find an average offset of 0.9‰ between leaves and grains in their δ(13) C values. The variation found is large enough to have archaeological implications and within- and between-plant isotope variability should be considered in isotope studies. The range in δ(15) N values is particularly significant as it is larger than the typical values quoted for a trophic level enrichment, and as such may lead to erroneous interpretations of the amount of animal protein in human or animal diets. It is therefore necessary to account for the variability in plant stable isotope values during palaeodietary reconstructions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis of carbon stable isotope to determine the origin and migration of gaseous hydrocarbon in the Brazilian sedimentary basins

International Nuclear Information System (INIS)

Takaki, T.; Rodrigues, R.

1986-01-01

The carbon isotopic composition of natural gases to determine the origin and gaseous hydrocarbon migration of Brazilian sedimentar basins is analysed. The carbon isotopic ratio of methane from natural gases depends on the process of gas formation and stage of organic matter maturation. In the geochemical surface exploration the biogenic gases are differentiated from thermogenic gases, because the last one is isotopically heavier. As the isotopic composition of methane has not changed during migration, the migrated gases from deeper and more mature source rocks are identified by its relative 13 C enrichment. The methane was separated from chromatography and and the isotopic analysis was done with mass spectrometer. (M.C.K.) [pt

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

Science.gov (United States)

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

2010-01-01

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

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

Science.gov (United States)

Sreemany, Arpita

2017-04-01

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

Carbon fixation and isotope discrimination by a crassulacean plant: dependence on the photoperiod.

Science.gov (United States)

Lerman, J C; Queiroz, O

1974-03-22

Variations of more than 1 percent are observed in the carbon-13 to carbon-12 ratio of extracts of leaves of the succulent Kalanchoe blossfeldiana when the photoperiod is changed from long to short days. This indicates that the mechanism of carbon fixation switches from the Calvin (C(3)) pathway to the Hatch-Slack (C(4)) pathway of primary enzymic operation. The variations observed in the isotope compositions are tentatively explained by a model.

Aragonite-Calcite Inversion During Biogenic Carbonate Sampling: Considerations for Interpreting Isotopic Measurements in Paleoclimate Studies

Science.gov (United States)

Waite, A. J.; Swart, P. K.

2011-12-01

As aragonite is the metastable polymorph of calcium carbonate, it lends itself to monotropic inversion to the more stable polymorph, calcite. This inversion is possible through an increase in the temperature and pressure conditions to which the sample is exposed and, although first noted nearly a century ago, has been primarily discussed in the context of sample roasting prior to analyses in paleoclimatological studies. Over the last several decades, however, researchers have found evidence to suggest that the friction associated with the sampling of biogenic carbonates via milling/drilling also induces inversion. Furthermore, this inversion may be associated with a shift in measured oxygen isotopic values and ultimately have significant implications for the interpretation of paleoclimatic reconstructions. Despite this, the isotopic heterogeneity of biogenic aragonite skeletons makes the effects of inversion challenging to test and the subject remains underrepresented in the literature. Here we present a first order study into the effects of milling on both the mineralogy and isotopic compositions measured in sclerosponges, corals, and molluscs. X-Ray diffraction analysis of samples hand ground with a mortar and pestle reveal 100% aragonitic skeletons. Conversely, samples milled with a computerized micromill show measurable inversion to calcite. On average, percent inversion of aragonite to calcite for individual specimens was 15% for sclerosponges, 16% for corals, and 9% for molluscs. Isotopic data from these specimens show that the higher the percentage of aragonite inverted to calcite, the more depleted the measured oxygen isotopic values. In the largest of the datasets (sclerosponges), it is evident that the range of oxygen isotope values from milled samples (-0.02 to +0.84%) exceeds the range in values for those samples which were hand ground and showed no inversion (+0.53 to +0.90%). This, coupled with the strong correlation between the two variables

Isotopic abundance analysis of carbon, nitrogen and sulfur with a combined elemental analyzer-mass spectrometer system

International Nuclear Information System (INIS)

Pichlmayer, F.; Blochberger, K.

1988-01-01

Stable isotope ratio measurements of carbon, nitrogen and sulfur are of growing interest as analytical tool in many fields of research, but applications were somewhat hindered in the past by the fact that cumbersome sample preparation was necessary. A method has therefore been developed, consisting in essential of coupling an elemental analyzer with an isotope mass spectrometer, enabling fast and reliable conversion of C-, N- and S-compounds in any solid or liquid sample into the measuring gases carbon dioxide, nitrogen and sulfur dioxide for on-line isotopic analysis. The experimental set-up and the main characteristics are described in short and examples of application in environmental research, food analysis and clinical diagnosis are given. (orig.)

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.

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

Science.gov (United States)

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

2018-05-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Jacoby, G [ed.

1980-12-01

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

Radiogenic Lead Isotopes and Time Stratigraphy in the Hudson River, New York

International Nuclear Information System (INIS)

Chillrud, Steven N.; Bopp, Richard F.; Ross, James M.; Chaky, Damon A.; Hemming, Sidney; Shuster, Edward L.; Simpson, H. James; Estabrooks, Frank

2004-01-01

Radionuclide, radiogenic lead isotope and trace metal analyses on fine-grained sediment cores collected along 160 km of the upper and tidal Hudson River were used to examine temporal trends of contaminant loadings and to develop radiogenic lead isotopes both as a stratigraphic tool and as tracers for resolving decadal particle transport fluxes. Very large inputs of Cd, Sb, Pb, and Cr are evident in the sediment record, potentially from a single manufacturing facility. The total range in radiogenic lead isotope ratios observed in well-dated cores collected about 24 km downstream of the plant is large (e.g., maximum difference in 206 Pb/ 207 Pb is 10%), characterized by four major shifts occurring in the 1950s, 1960s, 1970s and 1980s. The upper Hudson signals in Cd and radiogenic lead isotopes were still evident in sediments collected 160 km downstream in the tidal Hudson. The large magnitude and abrupt shifts in radiogenic lead isotope ratios as a function of depth provide sensitive temporal constraints that complement information derived from radionuclide analyses to significantly improve the precision of dating assignments. Application of a simple dilution model to data from paired cores suggests much larger sediment inputs in one section of the river than previously reported, suggesting particle influxes to the Hudson have been underestimated

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope aud Water Chemistry Characterizations

Science.gov (United States)

Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike; Bissada, Adry K.

2013-01-01

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41º32'N, 120º5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4 2-, respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth estimated

Assessment of Bacterial Degradation of Aromatic Hydrocarbons in the Environment by Analysis of Stable Carbon Isotope Fractionation

Energy Technology Data Exchange (ETDEWEB)

Meckenstock, Rainer U. [Eberhard-Karls University of Tuebingen, Center for Applied Geoscience (Germany)], E-mail: rainer.meckenstock@uni-tuebingen.de; Morasch, Barbara [University of Konstanz, Faculty of Biology (Germany); Kaestner, Matthias; Vieth, Andrea; Richnow, Hans Hermann [Center for Environmental Research, Department of Remediation Research (Germany)

2002-05-15

{sup 13}C/{sup 12}C stable carbon isotope fractionation was used to assess biodegradation in contaminated aquifers with toluene as a model compound. Different strains of anaerobic bacteria (Thauera aromatica, Geobacter metallireducens, and the sulfate-reducing strain TRM1) showed consistent {sup 13}C/{sup 12}C carbon isotope fractionation with fractionation factors between {alpha}C = 1.0017 and 1.0018. In contrast, three cultures of aerobic organisms, using different mono- and dioxygenase enzyme systems to initiate toluene degradation, showed variable isotope fractionation factors of {alpha}C = 1.0027 (Pseudomonasputida strain mt-2), {alpha}C = 1.0011 (Ralstonia picketii), and{alpha}C = 1.0004 (Pseudomonas putida strain F1). The great variability of isotope fractionation between different aerobic bacterial strains suggests that interpretation of isotope data in oxic habitats can only be qualitative. A soil column was run as a model system for contaminated aquifers with toluene as the carbon source and sulfate as the electron acceptor and samples were taken at different ports along the column. Microbial toluene degradation was calculated based on the {sup 13}C/{sup 12}C isotope fractionation factors of the batch culture experiments together with the observed {sup 13}C/{sup 12}C isotope shifts of the residual toluene fractions. The calculated percentage of biodegradation, B, correlated well with the decreasing toluene concentrations at the sampling ports and indicated the increasing extent of biodegradation along the column. The theoretical toluene concentrations as calculated based on the isotope values matched the measured concentrations at the different sampling ports indicating that the Rayleigh equation can be used to calculate biodegradation in quasi closed systems based on measured isotope shifts. A similar attempt was performed to assess toluene degradation in a contaminated, anoxic aquifer. A transect of groundwater wells was monitored along the main

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...

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...

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

Science.gov (United States)

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

2014-01-01

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

Carbon, Chlorine, and Hydrogen Isotope Fractionation in Transformation of TCE to Ethene by a Dehalococcoides Culture

NARCIS (Netherlands)

Kuder, T.; van Breukelen, B.M.; Vanderford, M.; Philip, P.

2013-01-01

Carbon (C), chlorine (Cl), and hydrogen (H) isotope effects were determined during dechlorination of TCE to ethene by a mixed Dehalococcoides (Dhc) culture. The C isotope effects for the dechlorination steps were consistent with data published in the past for reductive dechlorination (RD) by Dhc.

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

Science.gov (United States)

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

2017-08-01

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

Carbon and oxygen isotopes in carbonatites from Puna, Jujuy and Salta, Argentina

International Nuclear Information System (INIS)

Zappettini, Eduardo O.; Rubiolo, Daniel

1998-01-01

δ 13 and δ 18 O data from carbonatites indicate that bodies formed by crystallization of carbonate magma with subsequent formation of metasomatic and hydrothermal carbonatitic veins. The isotopic data are consistent with the available geochemical and petrologic information. (author)

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

Science.gov (United States)

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

2013-04-01

Stable carbon isotopes provide a powerful tool to assess carbon pools and their dynamics. Dissolved organic carbon (DOC) has been recognized to play an important role in ecosystem functioning and carbon cycling and has therefore gained increased research interest. However, direct measurement of 13C isotopic signature of carbon in the dissolved phase is technically challenging particularly using high temperature combustion. Until recently, mainly custom-made systems existed which were modified for coupling of TOC instruments with IRMS for simultaneous assessment of C content and isotopic signature. The variety of coupled systems showed differences in their analytical performances. For analysis of DOC high temperature combustion is recognized as best performing method, owing to its high efficiency of conversion to CO2 also for highly refractory components (e.g. humic, fulvic acids) present in DOC and soil extracts. Therefore, we tested high temperature combustion TOC coupled to IRMS (developed by Elementar Group) for bulk measurements of DOC concentration and 13C signature. The instruments are coupled via an Interface to exchange the carrier gas from O2 to He and to concentrate the derived CO2 for the isotope measurement. Analytical performance of the system was assessed for a variety of organic compounds characterized by different stability and complexity, including humic acid and DOM. We tested injection volumes between 0.2-3 ml, thereby enabling measurement of broad concentration ranges. With an injection volume of 0.5 ml (n=3, preceded by 1 discarded injection), DOC and 13C signatures for concentrations between 5-150 mg C/L were analyzed with high precision (standard deviation (SD) predominantly TOC-IRMS in comparison with other systems capable of determining C concentration and isotopic signatures. We recognize the advantages of this system providing: - High sample throughput, short measurement time (15 minutes), flexible sample volume - Easy maintenance

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.

Upper Campanian-Maastrichtian chronostratigraphy of the Skælskør-1 core, Denmark

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Anderskouv, Kresten; Bjerager, Morten

2015-01-01

The lithostratigraphy, calcareous nannofossil biostratigraphy, carbon- and oxygen-isotope stratigraphy and gamma-ray profile are presented for the Skælskør-1 core, eastern Denmark. The correlation of carbon isotopes to Gubbio (Italy) and ODP Site 762C (Indian Ocean) provides...... the chronostratigrahical framework of the core through a tie to magnetostratigraphy. Two new carbon-isotope excursions are defined for the uppermost Maastrichtian of the core and prove useful for long-distance correlation. Twenty stratigraphic tie-points are used for correlation of the upper Campanian......-Maastrichtian interval by combining carbon-isotope and gamma-ray variations. Significant dissimilarities in the gamma-ray profiles of the Danish Basin cores preclude the sole use of this tool for basin-scale correlations. Bulk oxygen-isotopes and semi-quantitative abundance changes in the warm-water calcareous...

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

Science.gov (United States)

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

2016-03-15

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

Carbon isotopic composition of legumes with photosynthetic stems from Mediterranean and desert habitats

International Nuclear Information System (INIS)

Nilsen, E.T.; Sharifi, M.R.

1997-01-01

The carbon isotopic compositions of leaves and stems of woody legumes growing in coastal mediterranean and inland desert sites in California were compared. The overall goal was to determine what factors were most associated with the carbon isotope composition of photosynthetic stems in these habitats. The carbon isotope signature (delta 13C) of photosynthetic stems was less negative than that of leaves on the same plants by an average of 1.51 +/- 0.42 per thousand. The delta 13C of bark (cortical chlorenchyma and epidermis) was more negative than that of wood (vascular tissue and pith) from the same plant for all species studied on all dates. Desert woody legumes had a higher delta 13C (less negative) and a lower intercellular CO2 concentration (Ci) (for both photosynthetic tissues) than that of woody legumes from mediterranean climate sites. Differences in the delta 13C of stems among sites could be entirely accounted for by differences among site air temperatures. Thus, the delta 13C composition of stems did not indicate a difference in whole-plant integrated water use efficiency (WUE) among sites. In contrast, stems on all plants had a lower stem Ci and a higher delta 13C than leaves on the same plant, indicating that photosynthetic stems improve long-term, whole-plant water use efficiency in a diversity of species

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

Carbon isotope discrimination by photosynthesis: implications for the bio- and geosciences

International Nuclear Information System (INIS)

Lerman, J.C.; Troughton, J.H.

1975-01-01

Land plants are depleted in the heavy isotopes of natural carbon 14 C (radioactive) and 13 C (stable) compared with the isotope composition of atmospheric CO 2 . These depletions can be assayed on milligram quantities of organic matter converted to CO 2 and analyzed in a double inlet-double collector mass spectrometer, the ratio 13 C/ 12 C usually being expressed as delta 13 C vs. PDB, in per mil ( 0 / 00 ). The delta value in higher plants ranges between -39 and -9 0 / 00 . The variations of this delta value are mainly determined by the type of carbon fixation reaction, e.g., the delta value allows us to distinguish between C 3 (Calvin-Benson) plants typically -28 0 / 00 , and C 4 (Hatch-Slack) plants typically -13 0 / 00 . These corrections are important for archaeologic and groundwater dating. Since the carbon delta values persist in dead and ancient plant remains such as wood, pollen, peat, soil, coal and oil, it is possible to investigate previous environmental conditions, past climate, paleoecology, plant interaction with the environment and evolution of photosynthetic mechanisms. The delta value also tags the commercial products derived from plants and animals allowing their origin to be traced in investigations of fraud. Some of these naturally labeled products have medical applications

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.

On the relations between the oceanic uptake of CO2 and its carbon isotopes

International Nuclear Information System (INIS)

Heimann, M.; Maier-Reimer, E.

1994-01-01

The recent proposals to estimate the oceanic uptake of CO 2 by monitoring the oceanic change in 13 C/ 12 C isotope ratio or the air-sea 13 C/ 12 C isotopic disequilibrium is reviewed. Because the history of atmospheric CO 2 and 13 CO 2 since preindustrial times is almost the same, the oceanic penetration depth of both tracers must be the same. This dynamic constraint permits the establishment of yet a third method to estimate the global ocean uptake of CO 2 from 13 C measurements. Using available observations in conjunction with canonical values for the global carbon cycle parameters the three methods yield inconsistent oceanic CO 2 uptake rates for the time period 1970-1990, ranging from 0 to over 3 GtC year -1 . However, uncertainties in the available carbon cycle data must be taken into account. Using a non-linear estimation procedure, a consistent scenario with an oceanic CO 2 uptake rate of 2.2±0.8 GtC year -1 can be established. The method also permits an investigation of the sensitivities of the different approaches. An analysis of the results of two three-dimensional simulations with the Hamburg Model of the Oceanic Carbon Cycle shows that the 13 C isotope indeed tracks the oceanic penetration of anthropogenic CO 2 . Because of its different time history, bomb produced radiocarbon, as measured at the time of GEOSECS, correlates much less well to excess carbon. (orig.)

Carbon isotope effects associated with Fenton-like degradation of toluene: Potential for differentiation of abiotic and biotic degradation

International Nuclear Information System (INIS)

Ahad, Jason M.E.; Slater, Greg F.

2008-01-01

Hydrogen peroxide (H 2 O 2 )-mediated oxygenation to enhance subsurface aerobic biodegradation is a frequently employed remediation technique. However, it may be unclear whether observed organic contaminant mass loss is caused by biodegradation or chemical oxidation via hydroxyl radicals generated during catalyzed Fenton-like reactions. Compound-specific carbon isotope analysis has the potential to discriminate between these processes. Here we report laboratory experiments demonstrating no significant carbon isotope fractionation during Fenton-like hydroxyl radical oxidation of toluene. This implies that observation of significant isotopic fractionation of toluene at a site undergoing H 2 O 2 -mediated remediation would provide direct evidence of biodegradation. We applied this approach at a field site that had undergone 27 months of H 2 O 2 -mediated subsurface oxygenation. Despite substantial decreases (> 68%) in groundwater toluene concentrations carbon isotope signatures of toluene (δ 13 C tol ) showed no significant variation (mean = - 27.5 ±0.3 per mille, n = 13) over a range of concentrations from 11.1 to 669.0 mg L -1 . Given that aerobic degradation by ring attack has also been shown to result in no significant isotopic fractionation during degradation, at this site we were unable to discern the mechanism of degradation. However, such differentiation is possible at sites where aerobic degradation by methyl group attack results in significant isotopic fractionation

Stable isotope composition of atmospheric carbon monoxide. A modelling study

International Nuclear Information System (INIS)

Gromov, Sergey S.

2014-01-01

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 13 C, δ 18 O and Δ 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 13 CO/ 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 13 C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH 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 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 13 C, were found significant when explicitly simulated. The

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

International Nuclear Information System (INIS)

Fontugne, M.

1991-01-01

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

Covalently bound molecular states in beryllium and carbon isotopes

International Nuclear Information System (INIS)

Wolfram von, Oertzen; Hans-Gerhard, Bohlen; Wolfram von, Oertzen

2003-01-01

Nuclear clustering in N=Z nuclei has been studied since many decades. States close to the decay thresholds, as described by the Ikeda diagram, are of particular interest. Recent studies in loosely bound systems, as observed with neutron-rich nuclei has revived the interest in cluster structures in nuclei, with additional valence neutrons, which give rise to pronounced covalent molecular structures. The Beryllium isotopes represent the first example of such unique states in nuclear physics with extreme deformations. In the deformed shell model these are referred to as super- and hyper-deformation. These states can be described explicitly by molecular concepts, with neutrons in covalent binding orbits. Examples of recent experiments performed at the HMI-Berlin demonstrating the molecular structure of the rotational bands in Beryllium isotopes are presented. Further work on chain states (nuclear polymers) in the carbon isotopes is in progress, these are the first examples of deformed structures in nuclei with an axis ratio of 3:1. A threshold diagram with clusters bound via neutrons in covalent molecular configurations can be established, which can serve as a guideline for future work. (authors)

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Present and future water resources in India: Insights from satellite remote sensing and ... of light gaseous hydrocarbons in near-surface soils of Kutch–Saurashtra: Implication .... Late Paleocene–early Eocene carbon isotope stratigraphy from a ...

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

International Nuclear Information System (INIS)

Sun Yanrong; Mu Zhiguo; Cui Haiting

2002-01-01

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

Preliminary study of lead isotopes in the carbonate-silica veins of Trench 14, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

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

1993-01-01

The sub-vertical carbonate-silica veins filling the Bow Ridge Fault, where exposed in Trench 14 on the east side of Yucca Mountain, carry a lead isotopic signature that can be explained in terms of local sources. Two isotopically distinguishable--silicate and carbonate--fractions of lead are recognized within the vein system as well as in overlying surficial calcrete deposits. The acid-insoluble silicate fraction is contributed largely from the decomposing Miocene volcanic tuff, which forms the wall rock of the fault zone and is a ubiquitous component of the overlying soil. Lead contained in the silicate fraction approaches in isotopic composition that of the Miocene volcanic rocks of Yucca Mountain, but diverges from it in some samples by being more enriched in uranogenic isotopes. The carbonate fraction of lead in both vein and calcrete samples resides dominantly in the HCl- and CH 3 COOH-soluble calcite. HCl evidently also attacks and removes lead from silicate phases, but the milder CH 3 COOH dissolution procedure oftentimes identifies a significantly more radiogenic lead in the calcite. Wind-blown particulate matter brought to the area from Paleozoic and Late Proterozoic limestones in surrounding mountains may be the ultimate source of the calcite. Isotopically more uniform samples suggest that locally the basaltic ash and other volcanic rock have contributed most of the lead to both fractions of the vein system. An important finding of this study is that the data does not require the more exotic mechanisms or origins that have been proposed for the veins. Instead, the remarkably similar lead isotopic properties of the veins to those of the soil calcretes support their interpretation as a surficial, pedogenic phenomenon

Preliminary study on the characteristics of carbon and oxygen isotopes in the Shiziping geothermal field groundwater in Emei Mountain

International Nuclear Information System (INIS)

Yu Xiujing; Jia Shuyuan

2000-01-01

Emei Mountain is a well-known scenic tourism spot in China. In order to promote the development of tourist trade, the authors have explored the hydrothermal water in Emei Mountain. At the beginning of 1998, the hydrothermal water was successfully drilled from the Shiziping geothermal field. In the process of prospecting the hydrothermal water, the authors adopted the geochemical method such as carbon and oxygen isotopes. The result indicates that the groundwater of different genetic types has different constitution characteristics of carbon and oxygen isotopes. This provides the important basis for finding out the forming conditions of underground hydrothermal water. So, it is prospective to study the growth characteristics of hydrothermal water with the carbon and oxygen isotopes of HCO 3 in groundwater

The stable carbon isotope ratios in benthic food webs of the gulf of Calvi, Corsica

Science.gov (United States)

Dauby, Patrick

1989-02-01

The Gulf of Calvi, Corsica, presents a wide diversity of biocoenoses, amongst which the seagrass Posidonia meadow is prevalent. More than 100 plant, animal and sediment samples from various biotopes were analysed for their stable carbon isotope ratios, to assess carbon flows within the food chains. Marine plants display a wide range of δ 13C values, from -6 to -32‰ but with three relatively well distinct peaks for Posidonia, brown algae and phytoplankton (-9, -19 and -23‰, respectively), which are the main carbon sources. The range of isotopic values of animals is narrower, from -14 to -24‰, suggesting that they feed mainly on algae and plankton. Computations based on simple equations show the proportion of each carbon source in the diet of the animals. Posidonia, notwithstanding their important biomass, appear to be a minor food source; this is possibly because of the transfer of their dead leaves, towards the shorelines, in winter.

BIOGENIC VS. ABIOGENIC ISOTOPE SIGNATURES OF REDUCED CARBON COMPOUNDS: A LESSON FROM HYDROTHERMAL SYNTHESIS EXPERIMENTS

International Nuclear Information System (INIS)

Horita, J.

2001-01-01

With growing interest in and demonstrated cases of inorganic hydrothermal synthesis of reduced or organic carbon compounds from CO and CO(sub 2), it becomes crucial to establish geochemical criteria to distinguish reduced/organic carbon compounds of abiogenic origin from those of biogenic origin with overwhelming abundances on the surface and in subsurface of the Earth. Chemical and isotopic compositions, particularly(sup 13)C/(sup 12)C ratios, of reduced/organic carbon compounds have been widely utilized for deducing the origins and formation pathways of these compounds. An example is isotopic and C(sub 1)/(C(sub 2)+C(sub 3)) ratios of natural gases, which have been used to distinguish bacterial, thermogenic, and possible abiogenic origins. Another example is that ancient graphitic carbon with(delta)(sup 13)C values c-25per thousand has been considered of biogenic origin. Although these criteria could be largely valid, growing data including those from our hydrothermal experiments suggest that a great caution must be exercised

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

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

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

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.

Biometrics from the carbon isotope ratio analysis of amino acids in human hair.