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Sample records for 18o 24mg 44ca

  1. Weak transition of 44Ca

    A study of the nuclear core contribution to the excited nuclear states was done, along with its theoretical evaluation and interpretation, in the light nuclei region. The 727 KeV gamma ray transition between the 1885 KeV O+ and 1157 KeV - 2+ states was detected, putting in evidence experimentally, the possibility of the 0+ state, characterized as core excitation, and found to be by + decay or electron capture from44,44mSc. The formation of the 2850 KeV state, due to 880 KeV transition from the 3667 KeV state, is re-discussed. The 564 KeV and 1684 KeV transitions from the 2850 KeV state to the 2285 KeV and 1157 KeV states, respectively, are also discussed. A new scheme is proposed for the 44Ca excited states. (Author)

  2. Isospin mixing in 24Mg

    We have used the #betta#-#betta# circular polarization (CP) correlation technique to measure the isospin-forbidden Fermi matrix element for the #betta#+ decay of 24Al to the 4+ T=1 state in 24Mg at E/sub x/=8.437 MeV. The 24Al activity was produced by bombarding a natural Mg target with 18 MeV protons. The #betta#-#betta# CP correlation was measured using a novel apparatus which featured good energy resolution in both the #betta# and #betta# arms. The CP sensitive #betta#-ray detector utilized a transmission-mode Compton polarimeter and a 12.7 cm x 15.2 cm NaI detector. The #betta# detector was a telescope with a 700 μm surface barrier detector and a 5.1 cm x 12.7 cm plastic scintillator. The #betta#-#betta# CP asymmetry A [defined by W(theta, t tilde) = 1 + t tilde v/c A tilde cos theta where t tilde is the photon helicity] was found to be A tilde = -0.145 +- 0.030. After applying a correction for feeding of the 8.437 MeV state from the analog state this value of A tilde corresponds to a charge dependent matrix element between the 9.5 MeV 4+T=1 and 8.4 MeV T=O levels of [+;O[H/sub CD/]4+;1>] = 106 +- 40 keV which is the largest matrix element of H/sub CD/ ever observed in #betta# decay. For comparison the charge dependent matrix element between the 9.5 MeV state and the 4.1 MeV 4+ state, previously measured in 24Na decays is only 5.4 +- 2.2 keV. Our exceptionally large value occurs because the 9.5 MeV T=1 and 8.4 MeV T=O states have very similar space and spin wavefunctions. This matrix element is consistent with predictions which ascribe the entire effect to Coulomb forces

  3. Flashing coherently rotating carbon sticks in $^{24}$Mg+$^{24}$Mg collision

    Zhao, M H; Merlo, O; Huang, M R; Li, Y; Wang, J S

    2013-01-01

    We analyze quasi-periodic oscillations in the angle-averaged ($\\Delta\\theta_{cm}\\simeq 90^\\circ\\pm 25^\\circ $)excitation functions for the $^{24}Mg+^{24}Mg$ elastic-inelastic scattering and $\\alpha$-transfer channels on the energy interval $E_{cm}=44.86-47.76$ MeV.The period of the energy structures, $\\simeq$0.81 MeV, is interpreted as inverse half-period ($\\simeq 5\\times 10^{-21}$ sec.) of coherent rotation of highly excited short-lived ($\\simeq 3.6\\times 10^{-21}$ sec.) chain of a length $\\simeq 30$ fm. The rotational wave packet coherence survives (i) the energy relaxation (fully mixing ergodic dynamics) for the strongly overlapping states with fixed total spins and (ii) the strong distortion of the motion upon a change of the total spin.The present discussion leads us to the question: Is rotational coherence of large molecules necessarily destroyed in the conventionally statistical limit of structureless (non-selective) continuum under the conditions of complete intramolecular energy redistribution and vi...

  4. 16O+8Be cluster structure in 24Mg

    16O + 8Be cluster structure in 24Mg has been identified by observing the breakup into ground state 160 and 8Be fragments following inelastic scattering of 24Mg projectiles. The spectrum of states observed is compared to that previously measured in the 12C + 12C breakup channel to obtain information on the partial decay widths. (author)

  5. Alpha-cluster states populated in 24Mg + 12C

    Charged particle and γ-decays in light α-like nuclei are investigated for 24Mg +12C. Various theoretical predictions for the occurrence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are presented. The inverse kinematics reaction 24Mg +12C is studied at Elab(24Mg) = 130 MeV. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. Coincident events from α-transfer channels were selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on 20Ne-γ and 16O-γ coincidences. (author)

  6. Molecular resonances and the Jacobi shape transition: the case of 24Mg+24Mg and 48Cr

    A fast rotating 48Cr is predicted to be highly prolate and deformed after a Jacobi shape transition and just before fission. In this article, it is proposed that an arrow and high spin 24Mg+24Mg resonance corresponds to the formation of this exotic 48Cr. Moreover the 24Mg+24Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV, where a narrow and high spin resonance has been reported previously. To establish the connection between the resonance and a molecular state of 48Cr, the decay of the resonance into the inelastic and fusion-evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the gamma array CLARA, and, for the fusion-evaporation channels, the Si array EUCLIDES and the gamma array GASP. Strong resonant effects have been observed in the inelastic channels involving the 2+ and 4+ states of the 24Mg ground state (g.s.) band. Weaker effects are also seen in certain fusion-evaporation channels. Both results will be discussed here. (authors)

  7. Neutron inelastic cross section measurements for 24Mg

    OLACEL A.; Borcea, C.; DESSAGNE Philippe; Kerveno, M.; NEGRET A.; PLOMPEN Arjan

    2014-01-01

    The gamma production cross sections from the neutron inelastic scattering on 24Mg were measured for neutron energies up to 18 MeV at GELINA (Geel Linear Accelerator), the neutron source operated by EC-JRC-IRMM, Belgium. The level cross section and the total inelastic cross section were determined. We used the GAINS (Gamma Array for Inelastic Neutron Scattering) spectrometer with 7 large volume HPGe detectors placed at 110◦ and 150◦ with respect to the beam direction. The neutron flux was dete...

  8. Hot fusion-evaporation cross sections of 44Ca-induced reactions with lanthanide targets

    Werke, T. A.; Mayorov, D. A.; Alfonso, M. C.; Tereshatov, E. E.; Folden, C. M.

    2015-11-01

    Background: Previously reported cross sections of 45Sc-induced reactions with lanthanide targets are much smaller than 48Ca-induced reactions on the same targets. 44Ca is one proton removed from 45Sc and could be used to produce nuclei with a relative neutron content between those produced in the 45Sc- and 48Ca-induced reactions. Purpose: As part of a systematic investigation of fusion-evaporation reactions, cross sections of 44Ca-induced reactions on lanthanide targets were measured. These results are compared to available data for 48Ca- and 45Sc-induced fusion-evaporation cross sections on the same lanthanide targets. Collectively, these data provide insight into the importance of the survival against fission of excited compound nuclei produced near spherical shell closures. Methods: A beam of 6+Ca at an energy of ≈5 MeV /u was delivered by the K500 superconducting cyclotron at the Cyclotron Institute at Texas A&M University. The desired evaporation residues were selected by the Momentum Achromat Recoil Spectrometer and identified via their characteristic α -decay energies. Excitation functions for the 44Ca+158Gd ,159Tb, and 162Dy reactions were measured at five or more energies each. A theoretical model was employed to study the fusion-evaporation process. Results: The 44Ca-induced reactions have x n cross sections that are two orders of magnitude larger than 45Sc-induced reactions but two orders of magnitude smaller than 48Ca-induced reactions on the same targets. Proton emission competes effectively with neutron emission for the 44Ca+159Tb and 162Dy reactions. The maximum 4 n cross sections in the 44Ca+158Gd ,159Tb, and 162Dy reactions were 2100 ± 230 ,230 ± 20 , and 130 ±20 μ b , respectively. The 44Ca+158Gd and 159Tb cross sections are in good agreement with the respective cross bombardments of 48Ca+154Gd and 45Sc+158Gd once differences in capture cross sections and compound nucleus formation probabilities are corrected for. Conclusions: Excitation

  9. Evidence of intermediate structure in 12C plus 24Mg system

    Studies of backward resonance structures have been performed for the 12C, 24Mg system at 1800 c.m. Excitation functions were measured using the 24Mg beam of the Saclay F.N. Van de Graaff and by detecting at 00 the 12C recoil nuclei with a QDDD magnetic spectrometer. Havar and/or gold foils were placed in front of the focal plane gas counter in order to stop the 24Mg beam. The target was made of a 50 μg/cm2 carbon layer plus a 10 μg/cm2 gold deposit for beam intensity monitoring. The results are presented between 11- and 27 MeV c.m. for the g.s. 0+, first 2+ state of 24Mg and first 2+ state of 12C. The step in energy is 133 keV c.m. The coulomb barrier is about 12 MeV. A certain correlation can be observed between the elastic and inelastic excitation functions. The coherence width calculated is about 600 keV for a average interval of 4.1 MeV c.m. The normalized cross-correlation coefficients are respectively -0.33 and -0.37 for correlation between g.s. and first 2+ of 24Mg and first 2+ of 12C. The cross-correlation cofficient between the two 2+ states is 0.01

  10. $^{24}$Mg($p$, $\\alpha$)$^{21}$Na reaction study for spectroscopy of $^{21}$Na

    Cha, S M; Kim, A; Lee, E J; Ahn, S; Bardayan, D W; Chipps, K A; Cizewski, J A; Howard, M E; Manning, B; O'Malley, P D; Ratkiewicz, A; Strauss, S; Kozub, R L; Matos, M; Pain, S D; Pittman, S T; Smith, M S; Peters, W A

    2015-01-01

    The $^{24}$Mg($p$, $\\alpha$)$^{21}$Na reaction was measured at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory in order to better constrain spins and parities of energy levels in $^{21}$Na for the astrophysically important $^{17}$F($\\alpha, p$)$^{20}$Ne reaction rate calculation. 31 MeV proton beams from the 25-MV tandem accelerator and enriched $^{24}$Mg solid targets were used. Recoiling $^{4}$He particles from the $^{24}$Mg($p$, $\\alpha$)$^{21}$Na reaction were detected by a highly segmented silicon detector array which measured the yields of $^{4}$He particles over a range of angles simultaneously. A new level at 6661 $\\pm$ 5 keV was observed in the present work. The extracted angular distributions for the first four levels of $^{21}$Na and Distorted Wave Born Approximation (DWBA) calculations were compared to verify and extract angular momentum transfer.

  11. Fission fragment angular distribution in 24Mg induced reactions on 192Os and 197Au

    Angular distributions of fission fragments have been measured in 24Mg + 192Os and 24Mg + 197Au reactions at Elab = 128 MeV which is close to entrance channel Coulomb barrier. Experimental angular anisotropies were in reasonably good agreement with those calculated using the statistical theory. Analysis of the angular distribution data of the present study and of our earlier measurement in 19F + 197Au reaction has shown that contribution from non-compound nucleus fission in these systems is not significant. (author)

  12. Reaction mechanism for the symmetric breakup of 24Mg following an interaction with 12C

    Data on the yield of the symmetric breakup of 24Mg as a function of beam energy are presented and compared with detailed calculations of the energy dependence. The 24Mg states seen in symmetric breakup agree with previously observed breakup states having spin and parities Jπ=4+,(6+),8+. The data allow the variations of yield for indivual states to be judged, as the beam energy is varied. The variation in the yield of the 4+ states is compared in detail with calculations assuming several possible compound nuclear or direct reaction mechanisms. It is concluded that a massive (12C) transfer or a simple statistical compound process are unlikely mechanisms, but that each of several other mechanisms is consistent with the data. ((orig.))

  13. Entrance channel dependence of back angle yields: orbiting in 24Mg+16O reaction

    The back-angle yields of the oxygen and carbon particles from the 24Mg+16O reaction have been measured at E/sub Lab/(24Mg) = 79.5 MeV by using reverse kinematics. Comparison with data for the 28Si+12C reaction forming the same compound nucleus at the same excitation energy and with very similar spin distribution, demonstrates a strong entrance channel effect which is favoring the break-up into the entrance channel with large excitation energy. This result qualitatively supports the picture of the formation of a long-lived orbiting complex whose structure and decay are dependent on the entrance channel. The compound nucleus contribution has been inferred to be less than 15% of the measured oxygen cross-section. 9 references

  14. Configuration analysis of the 6.0 MeV 4+ state in 24Mg

    The configuration of the 6.0 MeV 4+ state in 24Mg has been investigated using the inelastic electron scattering form factor for this level. It is shown that 1s-0d shell cannot describe the observed form factor successfully. The amount of Og shell admixture in this transition is estimated. Saxon-Woods wavefunctions and phase-shift analysis have been used. (Auth.)

  15. Electron scattering from 20Ne and 24Mg in a microscopic boson model

    It is shown that a mean-field approximation applied to the microscopically derived boson Hamiltonian yields a reasonable description of the form factors for both elastic and inelastic electron scattering from some sd-shell nuclei (20Ne, 24Mg). The results agree well with experimental data for the 0+ → 0+ and 0+ → 2+ transitions but much less so for the 0+ → 4+ transitions. Possible sources of the observed discrepancies are suggested

  16. Study and realization of heavy ion detectors. Application to the reaction 12C+24Mg

    The present study deals with elastic and inelastic scattering of 24 to 44 MeV center of mass 24Mg ions by 12C. The Strasbourg Q3D magnetic spectrograph has been used to measure the 1800 c.m. scattering cross-sections in detecting the corresponding recoiling ions at THETAsub(Lab) = 00. Statistical fluctuations are probably present. The 1,5 m long position sensitive focal plan hybride counter is described

  17. Study of the 28Si(16O,20Ne)24Mg reaction

    In this work, measurements of elastic and inelastic angular distributions in the system 16O+ 20Si and in the alpha transfer reactions 20Si(16O,20Ne)24Mg were made in the angular range of 200 0 and the transfer reaction 20Si(16O,12C)32S in the angular range 160 0 at the energy of Ecm = 31.57 MeV. Optical potential parameters and β2 deformation parameters as well as spectroscopic factors were determined for the alpha transfer reactions. (A.C.A.S.)

  18. Experimental study of the fast neutron scattering from 24Mg, 28Si and 32S

    Differential cross section measurements for neutron scattering from 24Mg, 28Si and 32S at 9.76 and 14.83 MeV incident neutron energies have been undertaken. The experimental technique is based on the time-of-flight method with a pulsed neutron beam. Scattered neutrons have been detected by a spectrometer composed of five detectors. Elastic and inelastic scattering cross sections for levels of up to 6 MeV excitation energy have been obtained for the angular range from 15 to 1600 in 50 steps. These measurements will be used in a coupled-channel analysis to extract potential and deformation parameters

  19. Fourier-transform microwave spectroscopy of 24Mg 35Cl generated by laser ablation

    Ohshima, Yasuhiro; Endo, Yasuki

    1993-10-01

    The rotational spectrum of 24Mg 35Cl in its X 2Σ + (ν=0 and 1 ) state has been observed in the 14 GHz region by using a Fourier- transform microwave spectrometer combined with a laser-ablation source. The radical was produced by the reaction of atomic Mg vaporized by 532 nm laser light with Cl 2 diluted in Ar. The present observation of the lowest N transition by a high-resolving power instrument has provided accurate hyperfine coupling constants associated with the 35Cl nucleus of this molecule.

  20. Clustering aspects in N = Z nucleus 24Mg studied by antisymmetized molecular dynamics

    Cluster structure of highly excited states of 24Mg has been investigated by the antisymmetrized molecular dynamics. Imposing the constraints on the expectation values of harmonic oscillator quanta, α+20Ne, 12C+12C and 6α cluster wave functions were generated without any a priori assumption. The isoscalar monopole excitation function is also calculated and reasonably agrees with the observation. It is found that α+20Ne, 12C+12C and 6α clusters appear as the prominent peaks in the strength function

  1. Study of the elastic scattering of {sup 32}S by {sup 24}Mg at low energies

    Hassanain, Mahmoud A., E-mail: mho1959@yahoo.com [Department of Physics, King Khalid University, Abha (Saudi Arabia); Ibraheem, Awad A. [Department of Physics, King Khalid University Physics Department, Al-Azhar University (Egypt)

    2015-12-15

    The elastic scattering angular distribution of {sup 32}S on {sup 24}Mg at energies ranging from 65 to 110 MeV has been analyzed in the framework of the double folding (DF) model, using different effective nucleon-nucleon (NN) interactions based on the M3Y-Reid interaction. The Pauli correlation, zero-range, and finite-range exchange parts of the NN interactions are considered in the folding procedure to treat the single nucleon knock-on exchange term (SNKE) in the optical model. Successful reproduction of the data has been obtained with all the potentials considered in the present study. It is clear that the effect of Pauli correlation increases as the energy increases. Our calculations are insensitive to the strength of the imaginary potential used in the fit of the experimental data. We find also that the threshold anomaly is less pronounced in the {sup 32}S + {sup 24}Mg system. Our reaction cross sections are compared with the data, and the consistency between the real and imaginary volume integrals are checked by the dispersion relation. (author)

  2. An interpretation of gross structures in the energy spectra of 12C (16O,α)24Mg reaction

    Recent studies of the 12C(16O,α)24Mg reaction at E(16O) = 145 Mev have revealed the existence of several broad states with E sub(X)(24Mg) = 20 to 60 MeV. The energies of these states have been taken as evidence that they are members of the 12C + 12C molecular band J sup(π) = (10+) through J sup(π) = (18+). Subsequent investigation of the properties of these states, however, has failed to reveal the expected partial width for 24Mg* → 12C + 12C. It is shown that these states can be interpreted as an extension of the 24Mg Yrast sequence which is populated by the well understood high spin selectivity of α particle evaporation from a 28Si compound nucleus. (Author)

  3. Splitting of ISGMR strength in the light-mass nucleus $^{24}$Mg due to ground-state deformation

    Gupta, Y K; Matta, J T; Patel, D; Peach, T; Hoffman, J; Yoshida, K; Itoh, M; Fujiwara, M; Hara, K; Hashimoto, H; Nakanishi, K; Yosoi, M; Sakaguchi, H; Terashima, S; Kishi, S; Murakami, T; Uchida, M; Yasuda, Y; Akimune, H; Kawabata, T; Harakeh, M N

    2015-01-01

    The isoscalar giant monopole resonance (ISGMR) strength distribution in $^{24}$Mg has been determined from background-free inelastic scattering of 386-MeV $\\alpha$ particles at extreme forward angles, including 0$^{\\circ}$. The ISGMR strength distribution has been observed for the first time to have a two-peak structure in a light-mass nucleus. This splitting of ISGMR strength is explained well by microscopic theory in terms of the prolate deformation of the ground state of $^{24}$Mg.

  4. An Analysis of the $^{12}$C+$^{24}$Mg Reaction Using A New Coupling Potential

    Boztosun, I

    2001-01-01

    We introduce a new coupling potential to explain the experimental data for the $^{12}$C+$^{24}$Mg system at numerous energies in the laboratory system from 16.0 MeV to 24.0 MeV. This new coupled-channels based approach involves replacing the usual first derivative coupling potential by a new, second-derivative coupling potential. This paper first shows and discusses the limitation of the standard coupled-channels theory in the case where one of the nuclei in the reaction is strongly deformed. Then, this new approach is shown to improve consistently the agreement with the experimental data and has made major improvement on all the previous coupled-channels calculations for this system.

  5. Nuclear transparency and the onset of strong absorption regime in the 12C+24Mg system

    Lichtenthäler, R.; Lépine-Szily, A.; Hussein, M. S.

    1999-10-01

    The elastic scattering of 12C+24Mg has been studied by means of a phase-shift analysis of 21 angular distributions ranging from Elab=16 MeV up to Elab=40 MeV. A tridimensional plot of the reflection coefficient of the S matrix as a function of the angular momentum and energy shows a well-defined region of energy, which separates two regimes: strong absorption for higher energies and the so-called ``anomalous transparency regime,'' recently observed in this system at low energies. The Argand diagrams of the S matrix in angular momentum space also present very contrasting behaviors in the two regions with very rapidly varying phases in the low energy region, which we associate with a parity dependent term in the S matrix directly related to significant coupling to the elastic transfer of a 12C nucleus.

  6. Nuclear transparency and the onset of strong absorption regime in the $^{12}C + ^{24}Mg$ system

    Lichtenthäler, R; Hussein, M S

    1999-01-01

    The elastic scattering of 12C+24Mg has been studied by means of a phase-shift analysis of 21 angular distributions ranging from Elab=16MeV up to Elab=40MeV. A tri-dimensional plot of the reflection coefficient of the S-matrix as a function of the angular momentum and the energy shows a well defined region of energy which separates two regimes: strong absorption for higher energies and the so called "anomalous transparency regime", recently observed in this system at low energies. The Argand diagrams of the S-matrix in angular momentum space also present very contrasting behaviours in the two regions with very rapidly varying phases in the low energy region, which we associate with a parity dependent term in the S-matrix directly related to significant coupling to the elastic transfer of a 12C nucleus.

  7. Cyclotron production of high purity 44m,44Sc with deuterons from 44CaCO3 targets

    Introduction: Due to its longer half-life, 44Sc (T1/2 = 3.97 h) as a positron emitter can be an interesting alternative to 68Ga (T1/2 = 67.71 min). It has been already proposed as a PET radionuclide for scouting bone disease and is already available as a 44Ti/44Sc generator. 44Sc has an isomeric state, 44mSc (T1/2 = 58.6 h), which can be co-produced with 44Sc and that has been proved to be considered as an in-vivo PET generator 44mSc/44Sc. This work presents the production route of 44mSc/44Sc generator from 44Ca(d,2n), its extraction/purification process and the evaluation of its performances. Methods: Irradiation was performed in a low activity target station using a deuteron beam of 16 MeV, which favors the number of 44mSc atoms produced simultaneously to 44Sc. Typical irradiation conditions were 60 min at 0.2 μA producing 44 MBq of 44Sc with a 44Sc/44mSc activity ratio of 50 at end of irradiation. Separations of the radionuclides were performed by means of cation exchange chromatography using a DGA® resin (Triskem). Then, the developed process was applied with bigger targets, and could be used for preclinical studies. Results: The extraction/purification process leads to a radionucleidic purity higher than 99.99% (43Sc, 46Sc, 48Sc < DL). 44mSc/44Sc labeling towards DOTA moiety was performed in order to get an evaluation of the specific activities that could be reached with regard to all metallic impurities from the resulting source. Reaction parameters of radiolabeling were optimized, reaching yields over 95%, and leading to a specific activity of about 10–20 MBq/nmol for DOTA. A recycling process for the enriched 44Ca target was developed and optimized. Conclusion: The quality of the final batch with regard to radionucleidic purity, specific activity and metal impurities allowed a right away use for further radiopharmaceutical evaluation. This radionucleidic pair of 44mSc/44Sc offers a quite interesting PET radionuclide for being further evaluated as an in

  8. Two-neutron transfer analysis of the 16O(18O,16O)18O reaction

    Ermamatov, M. J.; Cappuzzello, F.; Lubian, J.; Cubero, M.; Agodi, C.; Carbone, D.; Cavallaro, M.; Ferreira, J. L.; Foti, A.; Garcia, V. N.; Gargano, A.; Lay, J. A.; Lenzi, S. M.; Linares, R.; Santagati, G.; Vitturi, A.

    2016-08-01

    Recently a quantitative description of the two-neutron transfer reaction 12C(18O,16O)14C was performed and the measured cross sections were successfully reproduced [M. Cavallaro et al., Phys. Rev. C 88, 054601 (2013), 10.1103/PhysRevC.88.054601]. This task was accomplished by combining nuclear structure calculations of spectroscopic amplitudes and a full quantum description of the reaction mechanism. Verification of such a theoretical approach to other heavy nuclear systems is mandatory in order to use (18O,16O ) reactions to assess pair configurations in nuclear states. In this work we apply this methodology to the 16O(18O,16O)18O reaction at 84 MeV. Experimental angular distributions for the two-neutron transfer to the ground state and 21+ state of 18O were obtained using the MAGNEX spectrometer at INFN-LNS. The roles of one- and two-step processes are analyzed under the exact finite range coupled reaction channel and the second order distorted wave Born approximation. We conclude that the one-step transfer mechanism is dominant in this system.

  9. Study of the interaction potential between 12 C and 24 Mg: an example of anomalous transparency

    Complete angular distributions of the 12 C + 24 Mg elastic scattering were measured at ECM = 10.67 and 11.33 MeV, and from ECM = 12.0 to 16.0 MeV, using a 12 C beam produced at Pelletron Accelerator. This energy range is close to the Coulomb barrier of tue system, which is 12.53 MeV. Surprisingly all the angular distributions show strong oscillations even at energies bellow the Coulomb barrier. The angular distributions were fitted by optical model calculations and we determined the shallowest real potential, without continuous ambiguity. The main features of this potential are: very transparent even at the nuclear interior and strong dependence with energy of the real imaginary depths Vo and Wo. At five energies the inelastic scattering data were also analysed and well fitted by coupled-channels calculations. The optical potentials of all channels present the threshold anomaly and are well reproduced by dispersion relation calculations applied to the volume integrals of the optical potentials. (author). 50 refs., 41 figs., 12 tabs

  10. The intermediate energy elastic scattering of protons by α-cluster 20Ne and 24Mg nuclei

    The multiple diffraction scattering theory and the α-cluster model with dispersion have been applied for calculations of the observables for the elastic scattering of intermediate energy protons by 20Ne and 24Mg nuclei. The target nuclei are considered as composed of the core (16O nucleus) and additional α-clusters (one α-cluster for 20Ne nucleus and a dumb-bell α-cluster configuration for 24Mg nucleus). Taking into account the α-cluster configuration of the core, it was supposed that the additional α-cluster or center of mass of the dumb-bell are arranged with the most probability inside or outside of the core. The calculated observables for the elastic p–20Ne and p–24Mg scattering are in agreement with the existing experimental data. The influence of the deformed core contribution on the behavior of the calculated observables also is tested. (author)

  11. Ion microscopic imaging of calcium transport in the intestinal tissue of vitamin D-deficient and vitamin D-replete chickens: A 44Ca stable isotope study

    The intestinal absorption of calcium includes at least three definable steps; transfer across the microvillar membrane, movement through the cytosolic compartment, and energy-dependent extrusion into the lamina propria, Tracing the movement of calcium through the epithelium has been hampered by lack of suitable techniques and, in this study, advantage was taken of ion microscopy in conjunction with cryosectioning and use of the stable isotope 44Ca to visualize calcium in transit during the absorptive process. The effect of vitamin D, required for optimal calcium absorption, was investigated. Twenty millimolar 44Ca was injected into the duodenal lumen in situ of vitamin D-deficient and vitamin D-replete chickens. At 2.5, 5.0, and 20.0 min after injection, duodenal tissue was obtained and processed for ion microscopic imaging. At 2.5 min. 44Ca was seen to be concentrated in the region subjacent to the microvillar membrane in tissue from both groups. At 5.0 and 20.0 min, a similar pattern of localization was evident in D-deficient tissues. In D-replete tissues, the distribution of 44Ca became more homogenous, indicating that vitamin D increased the rate of transfer of Ca2+ from the apical to the basolateral membrane, a function previously ascribed to the vitamin D-induced calcium-binding protein (28-kDa calbindin-D). Quantitative aspects of the calcium absorptive process were determined in parallel experiments with the radionuclide 47Ca. Complementary information on the localization of the naturally occurring isotopes of calcium (40Ca) and potassium (39K) is also described

  12. Production of neutral pions below the nucleon-nucleon threshold in the reactions 24Mg(16O,π0)X and 24Mg(4He,π0)X

    In the present thesis the production of neutral pions in the reaction 24Mg(16O,π0)X at 24 and 33 MeV/u as well as in the reaction 24Mg(4He,π0)X at a projectile energy of 43 MeV/u was studied by means of a lead-glass Cherenkov detector. The measured energy spectra can be well described by a parametrization by means of 1/E e sup(- E/E0) analogously to the bremsstrahlung model. The decrease parameters extracted from this indicate a stopping time in the order of magnitude of 10-24s, which confirms the assumption that the pions are produced in the early phase of the reaction before the onset of the equilibration of the fused system. (orig./HSI)

  13. Characteristics of charged projectile fragments from 24Mg-emulsion interactions at 4.5 A GeV/c

    A total sample of 1719 inelastic interactions of 24Mg in emulsion at 4.5 A GeV/c has been used to study the characteristics of projectile fragments. The multiplicity and angular distributions of projectile fragments in interactions with different target components have been investigated. The projected angular distributions of fragments exhibit features of limiting fragmentation. These distributions are consistent with quantum-mechanical calculations using the Sudden approximation and shell-model functions

  14. Back-angle anomaly and coupling between seven reaction channels of 12C+24Mg using algebraic scattering theory

    We measured six fairly complete angular distributions of elastic, inelastic and α-transfer reactions of the 12C+24Mg system ar Ecm = 25.2 MeV. We performed coupled channels calculations using the Algebraic Scattering Theory with nuclear algebraic potential derived from nuclear phase shifts and using available structure informations for the inelastic coupling strengths. The back angle rise in the elastic cross section is fully explained by the couplings between elastic and transfer channels. (author)

  15. A comparison of spectroscopic models of low excitation 2+ states in 24Mg and 28Si using inelastic proton scattering

    Distorted Wave approximation analyses of the inelastic scattering of 49.5 MeV protons from 24Mg and 28Si are used to compare 2+ transition densities that were obtained from a standard shell model, deformed potential models and an SU(3) model of the low excitation spectroscopy of these nuclei. Analyzing power predictions do not reproduce the data adequately; the discrepancies indicating a deficiency in the transition mechanism prescription

  16. 18O enrichment in phosphorus pools extracted from soybean leaves.

    Pfahler, Verena; Dürr-Auster, Thilo; Tamburini, Federica; Bernasconi, M Stefano; Frossard, Emmanuel

    2013-01-01

    The objective of this study was to investigate the isotopic composition of oxygen bound to phosphate (δ(18)O-PO(4)) in different phosphorus (P) pools in plant leaves. As a model plant we used soybean (Glycine max cv Toliman) grown in the presence of ample P in hydroponic cultures. The leaf blades were extracted with 0.3 M trichloroacetic acid (TCA) and with 10 M nitric acid. These extractions allowed measurement of the TCA-soluble reactive P (TCA P) that is rapidly cycled within the cell and the total leaf P. The difference between total leaf P and TCA P yielded the structural P which includes organic P compounds not extractable by TCA. P uptake and its translocation and transformation within the soybean plants lead to an (18)O enrichment of TCA P (δ(18)O-PO(4) between 16.9 and 27.5‰) and structural P (δ(18)O-PO(4) between 42.6 and 68.0 ‰) compared with 12.4‰ in the phosphate in the nutrient solution. δ(18)O values of phosphate extracted from soybean leaves grown under optimal conditions are greater than the δ(18)O-PO(4) values of the provided P source. Furthermore, the δ(18)O-PO(4) of TCA P seems to be controlled by the δ(18)O of leaf water and the activity of inorganic pyrophosphatase or other pyrophosphatases. PMID:23106517

  17. Galactic interstellar 18O/17O ratios - a radial gradient?

    Wouterloot, J G A; Brand, J; Davis, G R

    2008-01-01

    (Abridged) Our aim is to determine 18O/17O abundance ratios across the entire Galaxy. These provide a measure of the amount of enrichment by high-mass versus intermediate-mass stars. Such ratios, derived from the C18O and C17O J=1-0 lines alone, may be affected by systematic errors. Therefore, the C18O and C17O (1-0), (2-1), and (3-2), as well as the 13CO (1-0) and (2-1) lines, were observed towards 18 prominent galactic targets (a total of 25 positions). The combined dataset was analysed with an LVG model, accounting for optical depth effects. The data cover galactocentric radii R between 0.1 and 16.9 kpc (solar circle at 8.5 kpc). Near the centre of the Galaxy, 18O/17O = 2.88 +/- 0.11. For the galactic disc out to an R of ca. 10 kpc, 18O/17O = 4.16 +/- 0.09. At ca. R = 16.5 kpc, 18O/17O = 5.03 +/- 0.46. Assuming that 18O is synthesised predominantly in high-mass stars (M > 8 Msun), while C17O is mainly a product of lower-mass stars, the ratio from the inner Galaxy indicates a dominance of CNO-hydrogen burni...

  18. Spin polarization of 23Mg in 24Mg + Au, Cu and Al collisions at 91 A MeV

    Spin polarization of beta-emitting fragment 23Mg(Iπ = 3/2+, Tl/2 = 11.3 s) produced through the projectile fragmentation process in 24Mg + Au, Cu and Al collisions has been observed at 91 A MeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant-spectator picture, for heavy and light targets. However the polarization behavior differs from this model in terms of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum

  19. Microscopic foundation of sdgIBM-2 and study of low-lying states of 24Mg

    A microscopic framework of sdIBM-2 is extended to the one of sdgIBM-2. Introducing hexadecupole pairing force, Hamiltonian and E2, E4 operators of the sdgIBM-2 are deduced microscopically. The nucleus 24Mg in the light-mass region is chosen as the first application of such an extended microscopic approach. Based on strong coupling picture, spectrum, reduced E2 transition rates and reduced E4 transition matrix elements are calculated. The calculated results fit experimental results quite well

  20. Study of delta18O calcite-dolomite mixtures

    Isotope ratio of oxygen in carbonate mixtures has been studied. For the purpose samples of calcite and dolomite with the known values delta18O are mixed in the ratios 9:1, 3:1, 1:1, 1:3, 1:9. Then from the mixtures prepared CO2 gas is separated using the McCrea method, delta18O of the gas is measured using mass-srectrometer. It has been established that to obtain delta18O calcite in the mixtures with calcite excess CO2 gas should be collected in the interval 15-30 min of the reaction duration and for the mixtures with dolomite excess - in the interval 5-15 min. To determine delta18O of dolomite the optimum time of CO2 gas collection for all the mixtures is 4-24 h

  1. Nuclear molecules and their deexcitation channels, case of Cr48 generated by the Mg24 + Mg24 resonant reaction

    This work is dedicated to the study of the resonance (E = 45,7 MeV, Jπ = 36+, Γ = 170 keV) of the Mg24 + Mg24 composite nucleus. The PRISMA fragment spectrometer combined with the CLARA gamma detector have been used to study the deexcitation through inelastic channels of the composite system. It is showed that the resonant flux is mainly observed in the inelastic channels involving the contributions 0+, 2+ and 4+ of the band based on the fundamental state of Mg24. This is in good agreement with the theoretical predictions of the molecular model of Uegaki and Abe. Only 30% of the resonant flux has been observed in the inelastic channels and in the transfer channels. The missing flux has been investigated in the fusion/evaporation deexcitation channels with the GASP gamma multi-detector. A weak resonant effect has been highlighted in some residual nuclei such as Ti45, Ca42 and K39. A link between the prolate di-nucleus Ca48 generated in Mg24 + Mg24 reaction and a Cr48 nucleus that has just undergone a Jacobi transition from oblate to prolate, has been discovered. To explain a part of the missing flux it is suggested that the dipolar giant resonance might feed very deformed nuclei through particle emission

  2. Separation of reaction mechanisms at low energy. Study of the reactions: 27Al(d,p) 28Al, 24Mg(d,p) 25Mg, and 24Mg(d, α) 22Na

    The two sets of angular distributions of (d,p) reactions on Al and Mg, measured between 2 and 6 MeV, have given the possibility to test, in analysing the statistical fluctuations of cross-section, the validity of the separation of their mean values in two parts, one 'direct', another given by the statistical mechanism. With the same method of analysis we have studied excitation functions for several alpha groups of the reaction 24Mg(d, α) 22Na and given an evidence for an intermediate structure for the alpha channel leading to the 3. excited state of 22Na. The angular distribution of the wide resonance at 15.9 MeV in 26Al has been obtained. (author)

  3. Three new bands of 18O16O18O by CW-CRDS between 6340 and 6800 cm−1

    Three very weak bands of the 18O16O18O isotopologue of ozone have been detected by high sensitivity CW-Cavity Ring Down Spectroscopy between 6340 and 6800 cm−1. They are vibrationally assigned as 2ν1+5ν3, ν1+4ν2+3ν3 and 3ν2+5ν3 and correspond to the highest frequency bands of this isotopologue detected so far. A total of 464, 318 and 194 transitions were rovibrationally assigned, respectively. The good agreement with theoretical values achieved for the derived band centres and rotational constants confirms the accuracy of the potential energy surface recently obtained via extensive ab initio calculations. A set of line intensities was measured and fitted to derive the first transition moment parameter of the three bands. The determined sets of effective Hamiltonian parameter and transition moment operators, as well as the experimental energy levels, were used to generate a complete list of 1526 transitions, provided as Supplementary materials. The calculated line-list allows generating a synthetic spectrum which reproduces satisfactorily the experimental spectrum. - Highlights: • Cavity Ring Down Spectroscopy of 18O16O18O between 6340 and 6800 cm−1. • 976 Transitions assigned to three vibrational bands. • Highest vibrational bands observed so far for the 18O16O18O isotopologue. • Effective operator modelling of the spectra. • Good agreement with ab initio values for the band centres and rotational constants

  4. Nuclear molecules and their deexcitation channels, case of Cr{sup 48} generated by the Mg{sup 24} + Mg{sup 24} resonant reaction; Molecules nucleaires et leurs modes de desexcitation: le cas du {sup 48}Cr et de la reaction resonante {sup 24}Mg + {sup 24}Mg

    Salsac, M.D

    2006-12-15

    This work is dedicated to the study of the resonance (E = 45,7 MeV, J{sup {pi}} = 36{sup +}, {gamma} = 170 keV) of the Mg{sup 24} + Mg{sup 24} composite nucleus. The PRISMA fragment spectrometer combined with the CLARA gamma detector have been used to study the deexcitation through inelastic channels of the composite system. It is showed that the resonant flux is mainly observed in the inelastic channels involving the contributions 0{sup +}, 2{sup +} and 4{sup +} of the band based on the fundamental state of Mg{sup 24}. This is in good agreement with the theoretical predictions of the molecular model of Uegaki and Abe. Only 30% of the resonant flux has been observed in the inelastic channels and in the transfer channels. The missing flux has been investigated in the fusion/evaporation deexcitation channels with the GASP gamma multi-detector. A weak resonant effect has been highlighted in some residual nuclei such as Ti{sup 45}, Ca{sup 42} and K{sup 39}. A link between the prolate di-nucleus Ca{sup 48} generated in Mg{sup 24} + Mg{sup 24} reaction and a Cr{sup 48} nucleus that has just undergone a Jacobi transition from oblate to prolate, has been discovered. To explain a part of the missing flux it is suggested that the dipolar giant resonance might feed very deformed nuclei through particle emission.

  5. Separation of reaction mechanisms at low energy. Study of the reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, and {sup 24}Mg(d, {alpha}) {sup 22}Na; Sur la separation des mecanismes de reaction a basse energie. Etude des reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, et {sup 24}Mg(d, {alpha}) {sup 22}Na

    Mermaz, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-06-01

    The two sets of angular distributions of (d,p) reactions on Al and Mg, measured between 2 and 6 MeV, have given the possibility to test, in analysing the statistical fluctuations of cross-section, the validity of the separation of their mean values in two parts, one 'direct', another given by the statistical mechanism. With the same method of analysis we have studied excitation functions for several alpha groups of the reaction {sup 24}Mg(d, {alpha}) {sup 22}Na and given an evidence for an intermediate structure for the alpha channel leading to the 3. excited state of {sup 22}Na. The angular distribution of the wide resonance at 15.9 MeV in {sup 26}Al has been obtained. (author) [French] Les deux ensembles de distributions angulaires des reactions (d,p) sur Al et Mg, mesures entre 2 et 6 MeV, nous ont permis, en analysant les fluctuations statistiques de sections efficaces, de verifier la possibilite de la separation de leurs valeurs moyennes en deux composantes: l'une 'directe', l'autre due au mecanisme statistique. Avec la meme methode d'analyse nous avons etudie les fonctions d'excitation des premiers groupes alpha de la reaction {sup 24}Mg(d,{alpha}) {sup 22}Na et mis en evidence une structure intermediaire pour la voie de reaction aboutissant au 3eme niveau de {sup 22}Na. Nous avons obtenu la distribution angulaire de la resonance large situee a une energie d'excitation de 15,9 MeV dans {sup 26}Al. (auteur)

  6. Detailed microscopic calculation of stellar electron and positron capture rates on 24Mg for O+Ne+Mg core simulations

    Few white dwarfs, located in binary systems, may acquire sufficiently high mass accretion rates resulting in the burning of carbon and oxygen under nondegenerate conditions forming a O+Ne+Mg core. These O+Ne+Mg cores are gravitationally less bound than more massive progenitor stars and can release more energy due to the nuclear burning. They are also amongst the probable candidates for low entropy r-process sites. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rekindle the interest in 8 - 10 M which develop O+Ne+Mg cores. Microscopic calculations of capture rates on 24Mg, which may contribute significantly to the collapse of O+Ne+Mg cores, using shell model and proton-neutron quasiparticle random phase approximation (pn-QRPA) theory, were performed earlier and comparisons made. Simulators, however, may require these capture rates on a fine scale. For the first time a detailed microscopic calculation of the electron and positron capture rates on 24Mg on an extensive temperature-density scale is presented here. This type of scale is more appropriate for interpolation purposes and of greater utility for simulation codes. The calculations are done using the pn-QRPA theory using a separable interaction. The deformation parameter, believed to be a key parameter in QRPA calculations, is adopted from experimental data to further increase the reliability of the QRPA results. The resulting calculated rates are up to a factor of 14 or more enhanced as compared to shell model rates and may lead to some interesting scenario for core collapse simulators. (author)

  7. Study of the angular correlations of light charged particles for the reaction 35CI (260 MeV) + 24Mg

    This work is focussed on the investigation of deformed nuclei. The asymmetric fusion-fission of light heavy-ions (A ≤60) with a high excitation energy (T ∼ 4 MeV) had lead to a large deformation of the compound nucleus at the scission point. The angular correlations between light particles (LP) and their emitting fragments has been used to probe the deformation of nucleus. Exclusive measurements were performed for the 35Cl (260 MeV) + 24Mg system leading to the 59Cu compound nucleus (CN). The comparison between the energy spectra of LP's and a statistical calculation carried out by a Monte-Carlo code CASCADE has suggested a deformation of 1.3 (for an oblate shape) of the CN within the frame work of fusion-evaporation process. The source velocity spectrum of α particles and angular correlations of LP's have showed that pre-scission and pre-equilibrium emissions are negligible in the present reaction. Finally the confrontation of the data with the statistical code GEMINI has pointed out the sequential emission character of the LP's from the fission fragments. (author)

  8. Analyses of electron and proton scattering to low excitation isoscalar states in 20Ne, 24Mg and 28Si

    Intermediate energy inelastic proton scattering differential cross section and polarization data from the 21+ states in 24Mg and 28Si and from the 41+ states in 28Si have been analysed using the Distorted Wave Approximation with large basis models of nuclear structure. These structure models were tested by use in analyses of the longitudinal form factors obtained from inelastic electron scattering, so that analyses of the intermediate energy (p,p') data from the same transitions are then sensitive tests of the two-nucleon t-matrix. Data from these and other 21+ transitions in 12C and 20Ne at 49 MeV (24 MeV in the case of 20Ne), were also analysed to compare models of t-matrices at lower energies. An ancilliary study of the momentum transfer dependence of effective charges has been made as both s-d shell and large basis structure models have been used to compare with form factor data up to momentum transfers of 2.5 fm-1. The deduced momentum dependence of the effective charges is significant

  9. Elastic and inelastic scattering of 400 MeV polarised deuterons on 12C, 24Mg, 40Ca nuclei

    This research thesis is based on an experiment of scattering of polarised 400 MeV deuterons on 12C, 24Mg, 40Ca nuclei, performed on the Saturne accelerator. The measured observables are the non-polarised cross section, and the powers of vector and tensor analysis. The author describes the experiment running and the installation, presents the various devices from source to detection and acquisition by the computer system. He reports the experiment compilation: reading of magnetic tapes, assessment and taking into account of the different experimental parameters. The calculation of scattering observables (cross section and powers of analysis) is performed by using experimental data. Spectra of these observables are represented for the different excited states of nuclei, after, should the occasion arise, Gaussian decomposition or background subtraction. The author reports the analysis of the obtained results. Results obtained for the three nuclei are compared between each other, and with scattering data for protons at similar energies which have already been measured. An analysis with a microscopic model is performed and the predictions of this model are compared with the obtained results

  10. Stellar neutrino energy loss rates due to 24Mg suitable for O+Ne+Mg core simulations

    Neutrino losses from proto-neutron stars play a pivotal role to decide if these stars would be crushed into black holes or explode as supernovae. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rejuvenate the interest in 8-10 M stars which develop O+Ne+Mg cores. Simulation results of O+Ne+Mg cores show varying results in converting the collapse into an explosion. The neutrino energy loss rates are important input parameters in core collapse simulations. Proton-neutron quasi-particle random phase approximation (pn-QRPA) theory has been used for calculation of neutrino energy loss rates due to 24Mg in stellar matter. The rates are presented on a detailed density-temperature grid suitable for simulation purposes. The calculated neutrino energy loss rates are enhanced up to more than one order of magnitude compared to the shell model calculations and favor a lower entropy for the core of these massive stars. (author)

  11. Stellar neutrino energy loss rates due to $^{24}$Mg suitable for O+Ne+Mg core simulations

    Nabi, Jameel-Un

    2011-01-01

    Neutrino losses from proto-neutron stars play a pivotal role to decide if these stars would be crushed into black holes or explode as supernovae. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rejuvenate the interest in 8-10 M$_{\\odot}$ stars which develop O+Ne+Mg cores. Simulation results of O+Ne+Mg cores show varying results in converting the collapse into an explosion. The neutrino energy loss rates are important input parameters in core collapse simulations. Proton-neutron quasi-particle random phase approximation (pn-QRPA) theory has been used for calculation of neutrino energy loss rates due to $^{24}$Mg in stellar matter. The rates are presented on a detailed density-temperature grid suitable for simulation purposes. The calculated neutrino energy loss rates are enhanced up to more than one order of magnitude compared to the shell model calculations and favor a lower entropy for the core of these massive stars.

  12. Decay studies of 59Cu* formed in the 35Cl + 24Mg reaction using the dynamical cluster-decay model

    Karthikraj, C.; Balasubramaniam, M.

    2013-02-01

    The reformulated dynamical cluster-decay model (DCM) is applied to study the decay of odd-A and non-α structured 59Cu* formed in the 35Cl+24Mg reaction at Elab=275 MeV. Here, the temperature (T)-dependent binding energies due to Krappe are used. The roles of Wigner and pairing energies in the fragmentation potential are explicitly shown in this work. For the temperature T=4.1898 MeV corresponding to Elab=275 MeV, the contribution of pairing vanishes and the resulting structure of the fragmentation potential due to Wigner term is shown. In addition to this, we have studied the role of factor α appearing in the inertia part of the equation of motion dictating the mass-transfer process. It is shown that this factor has significant effect in the structure of preformation probability values and hence in turn we see significant changes in the cross sections. We compare the cross sections of the measured charge distributions of the fission fragments for two limiting values of the parameter α with the experimental data. In order to fit the total cross-section values, a linear relation is obtained between the free parameter of the model ▵R and the factor α appearing in the hydrodynamical mass.

  13. Detailed microscopic calculation of stellar electron and positron capture rates on $^{24}$Mg for O+Ne+Mg core simulations

    Nabi, Jameel-Un

    2014-01-01

    Few white dwarfs, located in binary systems, may acquire sufficiently high mass accretion rates resulting in the burning of carbon and oxygen under nondegenerate conditions forming a O+Ne+Mg core. These O+Ne+Mg cores are gravitationally less bound than more massive progenitor stars and can release more energy due to the nuclear burning. They are also amongst the probable candidates for low entropy r-process sites. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rekindle the interest in 8 -- 10 M$_{\\odot}$ which develop O+Ne+Mg cores. Microscopic calculations of capture rates on $^{24}$Mg, which may contribute significantly to the collapse of O+Ne+Mg cores, using shell model and proton-neutron quasiparticle random phase approximation (pn-QRPA) theory, were performed earlier and comparisons made. Simulators, however, may require these capture rates on a fine scale. For the first time a detailed microscopic calculation of the electron and positron captur...

  14. The Importance Of Atmospheric {delta} {sup 18}O In Determining Leaf {delta} {sup 18}O In Oak And Pine

    Reynolds, C.E.; Saurer, M.; Siegwolf, R.T.W.

    2005-03-01

    Strongly {delta} {sup 18}O depleted water vapour was used to study leaf isotopic enrichment and gas exchange properties in a climate-controlled cuvette under a range of environmental conditions. Results show that water vapour strongly influences leaf isotopic composition. This technique was successfully introduced as a novel tool for studying leaf water enrichment. (author)

  15. 18O + 12C fusion-evaporation reaction

    A study of the 18O + 12C fusion evaporation reaction has been undertaken for 2 reasons: to make a systematic study of the formation cross section for each individual evaporation residue over a broad excitation energy region in the compound nucleus 30Si:30 to 62 MeV; and to compare all results to fusion-evaporation calculations done in the framework of the Hauser-Feschbach statistical model

  16. C18O Depletion in Starless Cores in Taurus

    Ford, Amanda Brady

    2011-01-01

    We present here findings for C18O depletion in eight starless cores in Taurus: TMC-2, L1498, L1512, L1489, L1517B, L1521E, L1495A-S, and L1544. We compare observations of the C18O J=2-1 transition taken with the ALMA prototype receiver on the Heinrich Hertz Submillimeter Telescope to results of radiative transfer modeling using RATRAN. We use temperature and density profiles calculated from dust continuum radiative transfer models to model the C18O emission. We present modeling of three cores, TMC-2, L1489, and L1495A-S, which have not been modeled before and compare our results for the five cores with published models. We find that all of the cores but one, L1521E, are substantially depleted. We also find that varying the temperature profiles of these model cores has a discernable effect, and varying the central density has an even larger effect. We find no trends with depletion radius or depletion fraction with the density or temperature of these cores, suggesting that the physical structure alone is insuff...

  17. Laser-based measurements of 18O/16O stable isotope ratios (δ18O in wine samples

    Gupta M

    2013-09-01

    Full Text Available Manish Gupta,1 J Brian Leen,1 Elena Simone Franklin Berman,1 Aldo Ciambotti2 1Los Gatos Research, Mountain View, CA, USA; 2Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Centro di Ricerca per l'Enologia, Asti, Italy Abstract: Wine counterfeiting is an international, multi-billion dollar issue, with some estimates suggesting that up to 5% of wines sold at auctions or secondary markets are fraudulent. Isotope ratio mass spectrometer (IRMS measurements of the 18O/16O stable isotope ratio (δ18O of water-in-wine have been used for wine authentication; however, these analyses are time-consuming and costly. In this preliminary study, off-axis integrated cavity output spectroscopy (OA-ICOS is used to quantify δ18O in wines. This laser-based method has been extensively used to study water isotopes for hydrological and medical applications. Recently, the development of a spectral contaminant identifier (SCI has extended the application of these OA-ICOS analyzers to contaminated water samples (eg, plant, soil, and leaf waters. Here, we utilize OA-ICOS with the SCI to characterize wine samples (9%–15% ethanol, and show that the laser-based instrument provides a δ18O measurement precision of ±0.07‰ (1σ and agrees with IRMS to within ±0.63‰ (1σ. Moreover, by training the SCI on isotopically-characterized wines, the agreement with IRMS improves to within ±0.30‰ (1σ. The utility of the instrument is demonstrated by measuring watered and mixed wines. The method presented here can be readily extended to address other food authentication applications. Keywords: wine isotopes, wine fraud, counterfeit wines, OA-ICOS

  18. Investigating the past and recent δ18O-accumulation relationship seen in Greenland ice cores

    Buchardt, S. L.; Clausen, H. B.; Vinther, B. M.; Dahl-Jensen, D.

    2012-01-01

    Decadal means of δ18O and accumulation rates from 52 ice core locations in Greenland are presented. The accumulation rates are derived from annual layers determined in the δ18O curve. Investigation of the δ18O-accumulation relationship across the ice divide reveals a significant Foehn effect with anticorrelation of δ18O and accumulation rate on the lee side of the divide in Southern Greenland, while no effect is seen in Central Greenl...

  19. Espiritu Santo, Vanuatu Stable Isotope (delta 18O, delta 13C) Data for 1806 to 1979

    National Oceanic and Atmospheric Administration, Department of Commerce — Site: Espiritu Santo Island, Vanuatu, 15S, 167E. 173 year record of d18O and d13C. Variable names: QSR Age, QSR 13C, QSR 18O, GRL Age, GRL Qtrly 13C, GRL Qtrly 18O,...

  20. An attempt of application of short lived 44K activity induced in the 44Ca(n,p)44K reaction using 14 MeV neutrons for total body calcium assessment in human subject

    The status of in vivo neutron activation analysis techniques for the measurement of total body calcium in human subject is reviewed. Relevant data on the nuclear characteristics of calcium isotopes during interaction with neutrons ranging from slow up to 14 MeV neutrons are presented. Physical aspects of the measurement of in vivo total body calcium (TBCa) using 44K activity induced in the 44Ca(n,p)44K(T1/2=22.3 min) reaction by 14 MeV neutrons are discussed. The measurement of delayed γ-ray emitted during decay of activities induced in enriched 44Ca, natCa, phantom filled with water solution of natural calcium and skeletal arm are considered. Results of measurements on the phantom and skeletal arm indicate a possibility to measure the TBCa using the 44K activity. (author)

  1. Alpha-spectroscopic factors from (d,6Li) and (3He,7Be) reactions on 12C,24Mg,40Ca and 58Ni

    An attempt has been made to compare the alpha-spectroscopic factors (Ssub(α)) resulting from (d,6Li) and (3He,7Be) reactions on 12C,24Mg,40Ca and 58Ni employing potentials characterizing the same potential family for the deuteron and for the 3He-channels and another set of potentials characterizing a particular potential family for 6Li and 7Be-channels respectively. It is found that the extracted spectroscopic factors for 12C,24Mg and 40Ca agree well, while that for the target 58Ni differs by an order of magnitude from the other two reactions. A possible reason has been discussed. (author)

  2. Mass spectra and fusion cross sections for 20Ne + 24Mg interaction at 55 MeV and 85 MeV

    Inclusive γ-spectra from the 20Ne + 24Mg interaction have been measured using 55 and 85 MeV 20Ne beams accelerated at the CYCLONE cyclotron of Louvain-la-Neuve. The identification of γ lines allows the determination of mass spectra in the region 12<=A<=43. Experimental results are compared with statistical model calculations. The total reaction and fusion cross sections are extracted. Cross sections for inelastic scattering, few nucleon transfers and deep inelastic scattering are estimated. (author)

  3. The study of nuclear structure of 76-78Kr and 24Mg nuclei in the frame work of interacting boson model

    The results of this work show that the IBM-1 provides a good description of even-even 76-78Kr and 24Mg isotopes of the nuclei. The interacting boson model can reproduce a considerable quantity of experimental data and gives useful indications where data are lacking. One observe the transitions between three limit symmetries of the model, corresponding to different nuclear shapes

  4. Semi empirical formula for electronic stopping power determination of 24Mg, 27Al and 28Si ions crossing Formvar foil in the ion energy domain of LSS theory

    We have determined continuous stopping power of heavy ions in thin Formvar foil for 28Si, 27Al and 24Mg ions over an energy range of (0.1–0.5) MeV/nucleon. Heavy Ions Elastic Recoil Detection Analysis (HI-ERDA) technique coupled with time of flight (ToF) spectrometer has been used to measure energy loss of charged particles in this thin absorber. Lindhard, Scharff and Schiott (LSS) theory compared with the corresponding determined stopping values in Formvar, shows significantly large deviations. However, a novel semi empirical expression has been proposed here and tested for better stopping power calculations at low velocity in the ion energy domain of LSS theory for 28Si, 27Al and 24Mg ions crossing thin Formvar foil. The results were compared to the obtained experimental stopping power data, predictions of LSS theory and also to those generated by SRIM-2010 computer code. The obtained results exhibit good agreement with experimental data. - Highlights: • Experimental stopping data has been obtained by using Heavy Ions Elastic Recoil Detection Analysis technique with Time of Flight spectrometer. • A new semi-empirical stopping formula based on LSS theory has been proposed for 28Si, 27Al and 24 Mg ions in Formvar foil. • This expression well fit the experimental stopping data at low energy in LSS domain

  5. Extreme alpha-clustering in the 18O nucleus

    Johnson, E D; Goldberg, V Z; Brown, S; Robson, D; Crisp, A M; Cottle, P D; Fu, C; Giles, J; Green, B W; Kemper, K W; Lee, K; Roeder, B T; Tribble, R E

    2009-01-01

    The structure of the 18O nucleus at excitation energies above the alpha decay threshold was studied using 14C+alpha resonance elastic scattering. A number of states with large alpha reduced widths have been observed, indicating that the alpha-cluster degree of freedom plays an important role in this N not equal Z nucleus. However, the alpha-cluster structure of this nucleus is very different from the relatively simple pattern of strong alpha-cluster quasi-rotational bands in the neighboring 16O and 20Ne nuclei. A 0+ state with an alpha reduced width exceeding the single particle limit was identified at an excitation energy of 9.9+/-0.3 MeV. We discuss evidence that states of this kind are common in light nuclei and give possible explanations of this feature.

  6. 2H and 18O Freshwater Isoscapes of Scotland

    Meier-Augenstein, Wolfram; Hoogewerff, Jurian; Kemp, Helen; Frew, Danny

    2013-04-01

    Scotland's freshwater lochs and reservoirs provide a vital resource for sustaining biodiversity, agriculture, food production as well as for human consumption. Regular monitoring of freshwaters by the Scottish Environment Protection Agency (SEPA) fulfils legislative requirements with regards to water quality but new scientific methods involving stable isotope analysis present an opportunity combining these mandatory monitoring schemes with fundamental research to inform and deliver on current and nascent government policies [1] through gaining a greater understanding of Scottish waters and their importance in the context of climate change, environmental sustainability and food security. For example, 2H and 18O isoscapes of Scottish freshwater could be used to underpin research and its applications in: • Climate change - Using longitudinal changes in the characteristic isotope composition of freshwater lochs and reservoirs as proxy, isoscapes will provide a means to assess if and how changes in temperature and weather patterns might impact on precipitation patterns and amount. • Scottish branding - Location specific stable isotope signatures of Scottish freshwater have the potential to be used as a tool for provenancing and thus protecting premium Scottish produce such as Scottish beef, Scottish soft fruit and Scottish Whisky. During 2011 and 2012, with the support of SEPA more than 110 samples from freshwater lochs and reservoirs were collected from 127 different locations across Scotland including the Highlands and Islands. Here we present the results of this sampling and analysis exercise isotope analyses in form of 2H and 18O isoscapes with an unprecedented grid resolution of 26.5 × 26.5 km (or 16.4 × 16.4 miles). [1] Adaptation Framework - Adapting Our Ways: Managing Scotland's Climate Risk (2009): Scotland's Biodiversity: It's in Your Hands - A strategy for the conservation and enhancement of biodiversity in Scotland (2005); Recipe For Success - Scotland

  7. Quantitative fundamental SIMS studies using {sup 18}O implant standards

    Williams, Peter [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States)]. E-mail: pw@asu.edu; Sobers, Richard C. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States); Franzreb, Klaus [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States); Loerincik, Jan [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States)

    2006-07-30

    The use of dilute 'minor-isotope'{sup 18}O implant reference standards for quantification of surface oxygen levels during steady-state SIMS depth profiling is demonstrated. Some results of two types of quantitative fundamental SIMS studies with oxygen ({sup 16}O) primary ion bombardment and/or oxygen flooding (O{sub 2} gas with natural isotopic abundance) are presented: (1) Determination of elemental useful ion yields, UY(X{sup {+-}}), and sample sputter yields, Y, as a function of the oxygen fraction c {sub O} measured in the total flux emitted from the sputtered surface. Examples include new results for positive secondary ion emission of several elements (X = B, C, O, Al, Si, Cu, Ga, Ge, Cs) from variably oxidized SiC or Ge surfaces. (2) The dependence of exponential decay lengths {lambda}(Au{sup {+-}}) in sputter depth profiles of gold overlayers on silicon on the amount of oxygen present at the sputtered silicon surface. The latter study elucidates the (element-specific) effects of oxygen-induced surface segregation artifacts for sputter depth profiling through metal overlayers into silicon substrates.

  8. Activation cross section measurements near threshold for the 24Mg(n,p)24Na and 27Al(n,α)24Na reactions

    Differential cross sections have been measured for the 24Mg(n,p)24Na and 27Al(n,α)24Na reactions in the neutron energy range from near-threshold to approx. 10 MeV using 238U fast-neutron fission as a cross section standard. The present data generally support previous work, although the cross sections tend to be somewhat larger for 27Al(n,α)24Na, particularly in the 8-9 MeV range. These data contribute significantly to reducing the uncertainty in contemporary knowledge of the cross sections for these reactions in the threshold region. (author)

  9. Monsoon influence on planktic δ18O records from the South China Sea

    Wang, Pinxian; Li, Qianyu; Tian, Jun; He, Juan; Jian, Zhimin; Ma, Wentao; Dang, Haowen

    2016-06-01

    While the benthic δ18O records from many South China Sea sites mimic the SPECMAP/LR04 standard, their paired planktic δ18O curves differ by comparable values at negative peaks corresponding to interstadials, especially between MIS 5.1, 5.3, 5.5, 6.5, and 7.3. Similar planktic δ18O records also occur in some other low-latitude oceans under monsoon influence. Because neither temperature nor salinity effects can fully account for the variations of such δ18O records after derivation from the SPECMAP/LR04 standard, variations in the rain water δ18O affected by regional hydroclimate changes are considered to have played an important role. In contrast to the SPECMAP/LR04 standard δ18O curve prevailed by 100-kyr cycles, these regional planktic δ18O curves are distinguished by 20-kyr precession signal, showing partial similarity to the δ18O records of atmospheric oxygen in polar ice-core bubbles and in stalagmite calcite. We speculate that the common features of these three independent δ18O records are indicative of the effect of evolving hydrological cycling driven by monsoon circulation in low latitudes.

  10. A ‘hidden’ 18O-enriched reservoir in the sub-arc mantle

    Chuan-Zhou Liu; Fu-Yuan Wu; Sun-Lin Chung; Qiu-Li Li; Wei-Dong Sun; Wei-Qiang Ji

    2014-01-01

    Plate subduction continuously transports crustal materials with high-δ18O values down to the mantle wedge, where mantle peridotites are expected to achieve the high-δ18O features. Elevated δ18O values relative to the upper mantle value have been reported for magmas from some subduction zones. However, peridotites with δ18O values significantly higher than the well-defined upper mantle values have never been observed from modern subduction zones. Here we present in-situ oxygen isotope data of ...

  11. γ-ray production by proton and α-particle induced reactions on 12C, 16O, 24Mg, and Fe

    γ-ray production cross sections for proton and α-particle interactions with 12C, 16O, 24Mg, and Fe have been measured in the energy range 5-25 MeV with proton beams and 5-40 MeV with α-particle beams. Isotopically pure foils of 24Mg and foils of natural isotopical composition of C, MgO, and Fe have been used. γ-ray angular distributions were obtained with five high-purity Ge detectors with bismuth germanate Compton shields placed at angles of 45 deg. to 157.5 deg. Cross sections for more than 50 different γ-ray transitions were extracted, and for many of them no data have been published before. Comparison of present data with data available in the literature shows mostly good to excellent agreement. In addition to the production cross sections, high-statistics, low-background line shapes of the 4.438 MeV 12C γ ray from inelastic scattering off 12C and spallation of 16O were obtained. Comparison with nuclear reaction calculations shows that these data place interesting constraints on nuclear reaction models

  12. 24Mg(α,γ)28Si reaction at alpha-particle energies from 3.2 to 6.2 MeV

    The 24Mg(α,γ)28Si reaction has been used to study excited states in 28Si. Targets of enriched 24Mg on a tantalum backing were bombarded by an α-particle beam from the CN Van de Graaff accelerator of The Pennsylvania State University. A large NaI(Tl) detector was placed immediately adjacent to the target in order to increase the probability of summing of the signals from different members of a cascade; windows were set for transitions to the ground state and the first few excited states. The energy of the α-particles was increased in steps of 2 to 5 keV from 3.2 to 6.2 MeV. Thirty-two resonances were located by sharp increases in the number of events recorded. At each resonance a spectrum was taken using a 55 cm3 Ge(Li) detector placed 5 cm from the target at an angle of 550 to the beam axis, the data being recorded on a PDP-15 on-line computer. The spectra were analyzed off-line using the program SAMPO of the Lawrence Berkeley Laboratory. (Diss. Abstr. Int., B)

  13. Dirac Coupled-channel Analyses of Polarized Proton Scatterings to the 2$^+$ Gamma Vibrational Band in $^{24}$Mg and $^{26}$Mg

    Shim, Sugie

    2016-01-01

    Dirac coupled channel calculations are performed phenomenologically for the high-lying excited states that belong to the 2$^+$ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from the s-d shell nuclei, $^{24}$Mg and $^{26}$Mg. Optical potential model is used and scalar and time-like vector potentials are considered as direct potentials. First-order vibrational collective models are used to obtain the transition optical potentials in order to accommodate the high-lying excited vibrational collective states. The complicated Dirac coupled channel equations are solved phenomenologically to reproduce the differential cross section and analyzing power data by varying the optical potential and deformation parameters. It is found that the relativistic Dirac coupled channel calculation could describe the high-lying excited states of the 2$^+$ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from s-d shell nuclei $^{24}$Mg and $^{26}$Mg reasonably well, showing b...

  14. Variation in leaf water delta D and delta 18O values during the evapotranspiration process

    A theoretical model was developed to evaluate leaf water delta D and delta 18O variation in relation to: leaf temperature, relative humidity converted to leaf temperature and delta D and delta 18O values of atmospheric water vapour and soil water. (M.A.C.)

  15. $^{8}$Be, $^{12}$C, $^{16}$O, $^{20}$Ne, $^{24}$Mg, and $^{32}$S nuclei and alpha clustering within a generalized liquid drop model

    Royer, G; Eudes, P

    2015-01-01

    The potential energy governing the shape and the entrance and decay channels of the 12 C, 16 O, 20 Ne, 24 Mg, and 32 S 4n-nuclei has been determined within a generalized liquid drop model. Different three-dimensional and planar shapes have been investigated: linear chain, triangle, square, tetrahedron, pentagon, trigonal bipyramid, square pyramid, hexagon, octahedron, octogon and cube. The rms radii of the linear chains are higher than the experimental rms radii of the ground states. The binding energies of the planar shapes at the contact point are lower than the ones of the three-dimensional configurations. The a particle plus A-4 daughter configuration leads always to the lowest potential barrier relatively to the sphere configuration.

  16. Study of two- and multi-particle correlations in 12C+24Mg and 12C+208Pb reactions at E=35 AMeV

    Quattrocchi L.

    2016-01-01

    Full Text Available Two and multi particle correlations from the decay of sources produced in 12C+24Mg and 12C+208Pb collisions at E=35 AMeV have been studied by using the forward part (1° < θlab < 30° of the CHIMERA multi-detector. Correlations and invariant mass spectroscopy are used to explore simultaneous and sequential decays of resonances in light isotopes with Z∼3-6, produced in peripheral collisions via the break-up of excited quasi-projectiles. Among them we mention 5Li, 6Li, 6Be, 8Be and the astrophysically important state in 12C decaying into three alpha particles. Results and future perspectives at the INFN-LNS will be presented.

  17. Clustering effects in fusion evaporation reactions with light even-even N = Z nuclei. The {sup 24}Mg and {sup 28}Si cases

    Morelli, L., E-mail: luca.morelli@bo.infn.it; D’Agostino, M.; Bruno, M. [Dipartimento di Fisica e Astronomia dell’Università and INFN, Bologna (Italy); Baiocco, G. [Dipartimento di Fisica dell’Università and INFN, Pavia (Italy); Gulminelli, F. [CNRS, LPC, Caen, France and ENSICAEN, Caen (France); Cinausero, M.; Gramegna, F.; Marchi, T. [INFN, Laboratori Nazionali di Legnaro, Legnaro (Padova) (Italy); Degerlier, M. [University of Nevsehir, Physics Department, Nevsehir (Turkey); Fabris, D. [INFN, Sezione di Padova, Padova (Italy); Barlini, S.; Bini, M.; Casini, G.; Gelli, N.; Olmi, A.; Pasquali, G.; Piantelli, S. [Dipartimento di Fisica e Astronomia dell’Università and INFN, Firenze (Italy)

    2015-10-15

    In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. Within the currently ongoing experimental campaign by the NUCL-EX collaboration we have measured the {sup 12}C+{sup 12}C and {sup 14}N+{sup 10}B reactions at 95 MeV and 80 MeV respectively, and compared experimental data corresponding to complete fusion of target and projectile into an excited {sup 24}Mg nucleus to the results of a pure statistical model[3, 4]. We found clear deviations from the statstical model in the decay pattern: emission channels involving multiple α particles are more probable than expected from a purely statistical behavior. To continue the investigation on light systems, we have recentely measured the {sup 16}O+{sup 12}C reaction at three different beam energies, namely E{sub beam} = 90, 110 and 130 MeV.

  18. Clustering effects in fusion evaporation reactions with light even-even N = Z nuclei. The 24Mg and 28Si cases

    In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. Within the currently ongoing experimental campaign by the NUCL-EX collaboration we have measured the 12C+12C and 14N+10B reactions at 95 MeV and 80 MeV respectively, and compared experimental data corresponding to complete fusion of target and projectile into an excited 24Mg nucleus to the results of a pure statistical model[3, 4]. We found clear deviations from the statstical model in the decay pattern: emission channels involving multiple α particles are more probable than expected from a purely statistical behavior. To continue the investigation on light systems, we have recentely measured the 16O+12C reaction at three different beam energies, namely Ebeam = 90, 110 and 130 MeV

  19. The origin of high δ18O zircons: marbles, megacrysts, and metamorphism

    Cavosie, Aaron J.; Valley, John W.; Kita, Noriko T.; Spicuzza, Michael J.; Ushikubo, Takayuki; Wilde, Simon A.

    2011-11-01

    The oxygen isotope ratios (δ18O) of most igneous zircons range from 5 to 8‰, with 99% of published values from 1345 rocks below 10‰. Metamorphic zircons from quartzite, metapelite, metabasite, and eclogite record δ18O values from 5 to 17‰, with 99% below 15‰. However, zircons with anomalously high δ18O, up to 23‰, have been reported in detrital suites; source rocks for these unusual zircons have not been identified. We report data for zircons from Sri Lanka and Myanmar that constrain a metamorphic petrogenesis for anomalously high δ18O in zircon. A suite of 28 large detrital zircon megacrysts from Mogok (Myanmar) analyzed by laser fluorination yields δ18O from 9.4 to 25.5‰. The U-Pb standard, CZ3, a large detrital zircon megacryst from Sri Lanka, yields δ18O = 15.4 ± 0.1‰ (2 SE) by ion microprobe. A euhedral unzoned zircon in a thin section of Sri Lanka granulite facies calcite marble yields δ18O = 19.4‰ by ion microprobe and confirms a metamorphic petrogenesis of zircon in marble. Small oxygen isotope fractionations between zircon and most minerals require a high δ18O source for the high δ18O zircons. Predicted equilibrium values of Δ18O(calcite-zircon) = 2-3‰ from 800 to 600°C show that metamorphic zircon crystallizing in a high δ18O marble will have high δ18O. The high δ18O zircons (>15‰) from both Sri Lanka and Mogok overlap the values of primary marine carbonates, and marbles are known detrital gemstone sources in both localities. The high δ18O zircons are thus metamorphic; the 15-25‰ zircon values are consistent with a marble origin in a rock-dominated system (i.e., low fluid(external)/rock); the lower δ18O zircon values (9-15‰) are consistent with an origin in an external fluid-dominated system, such as skarn derived from marble, although many non-metasomatized marbles also fall in this range of δ18O. High δ18O (>15‰) and the absence of zoning can thus be used as a tracer to identify a marble source for high δ18O

  20. TDA's validity to study 18O collectivity in terms of collective pair model

    Conclusion proved that if the authors calculate 18O collective spectra in terms of the Collective Pair Model, the authors can get the positive low laying levels of 18O which are of the particle particle pair, independent on the excitation of hole within closed shell. 1- low laying levels are of non-collective 3 particle 1 hole states. 1- fourth level is of collective 3 particle 1 hole states. 3- low laying levels are of collective 3 particle 1 hole states. 1-, 3- low laying levels agree very well with the experiment data. Hence the TDA is sufficient for the calculations of 1-,3- collective low levels of 18O

  1. Determination of 13C and 18O isotopic abundances of carboxyl substances; application to amino acids

    Flash pyrolysis of organic acids or of their salts gives off carbon dioxide which can be analysed by mass spectrometry for 13C and 18O abundance. This principle has been applied to Cd13C18O3 using an induction furnace, and used to determine the 13C and 18O content of the carboxylic group of some amino acids. The technique described has many advantages over the classical pyrolysis methods using sealed tubes. It is rapid and simple and especially effective in determining the isotopic composition of hygroscopic carboxyl substances. (U.K.)

  2. Implications of the 14C(α,γ)18O reaction for nonstandard big bang nucleosynthesis

    The thermonuclear burning rates for the 14C(α,γ)18O radiative capture reaction are calculated at temperatures (0.3- state, at approximately 9.0 MeV in 18O as would be deduced from the Yale-Michigan State University measurement of the beta-delayed alpha-particle emission of 18N and suggested by the Notre Dame-Caltech measurement of the nonresonant 14C(α,γ)18O cross section. The gamma widths of the proposed broad state is estimated using the Alhassid, Gai, and Bertsch sum rule, and an experimental study is proposed

  3. Barbados Oxygen Isotope Data (delta 18O) for the Late Pleistocene

    National Oceanic and Atmospheric Administration, Department of Commerce — Coral-based delta18O time-series derived from measurements made on submerged or drowned coral reef sequence. The core samples used have been described elsewhere...

  4. Ras Umm Sidd Oxygen Isotope (delta 18O) Data for 1750 to 1995

    National Oceanic and Atmospheric Administration, Department of Commerce — Ras Umm Sidd bimonthly coral oxygen isotope data (coral core RUS-95). Notes on the data: File (Ras Umm Sidd d18O.txt.) includes columns for Year AD (bimonthly...

  5. Secas Island Stable Isotope Data (delta 18O) for 1707 to 1984

    National Oceanic and Atmospheric Administration, Department of Commerce — Secas Island Coral d18O, used to reconstruct seasonal and interannual variability in the Intertropical Convergence Zone. Site Location: Secas Island, Gulf of...

  6. Mahe, Seychelles Stable Isotope (delta 18O) Data for 1846 to 1995

    National Oceanic and Atmospheric Administration, Department of Commerce — Seychelles coral oxygen-18 time series, data are monthly values of d18O from July 1846 to February 1995 from a 3-m Porites lutea coral colony collected from Beau...

  7. Malindi, Kenya Stable Isotope Data (delta 18O, delta 13C) for 1801-1994

    National Oceanic and Atmospheric Administration, Department of Commerce — Malindi annual oxygen isotopic composition, 1801-1994. Notes on the data: File includes columns for Year AD, Coral d18O, and SST (degrees C). The SST data are...

  8. Evaluating the effects of evapotranspiration on the δ18O value of atmospheric moisture above vegetation

    Plants are major transducers of water and energy between the land surface and the atmosphere. This poster presents the use of stable isotopes (δ18O) to estimate transportation flux from vegetation. 4 refs, 2 tabs

  9. Enhancing the Accuracy of Carbonate δ18O and δ13C Measurements by SIMS

    Orland, I. J.; Kozdon, R.; Linzmeier, B.; Wycech, J.; Sliwinski, M.; Kitajima, K.; Kita, N.; Valley, J. W.

    2015-12-01

    The precision and accuracy of carbonate δ18O & δ13C analysis by multicollector SIMS is well established if standards match samples in structure and major/minor element chemistry. However, low-T- and bio-carbonates used to construct paleoclimate archives can include complex internal structures and some samples analyzed at WiscSIMS (and other SIMS labs) have a consistent, sample-dependent offset between average SIMS δ18O measurements and bulk δ18O analyses by phosphoric-acid digestion. The offset is typically hydrogen peroxide), for which there is no agreed procedure in conventional bulk analyses. For SIMS analyses, pre-treatments had varied influence on the δ18O value, [16O1H], the concentration of "organic markers" like 12C14N and 31P, and mineralogy (of aragonite samples).

  10. Body composition among Sri Lankan infants by 18*O dilution method and the validity of anthropometric equations to predict body fat against 18*O dilution

    Body composition indicators provide a better guidance for growth and nutritional status of the infants. This study was designed to (1) measure the body composition of the Sri Lankan infants using a reference method, the 18*O dilution method; (2) calculate the body fat content of the infants using pu...

  11. Climatic significance of δ18O records from precipitation on the western Tibetan Plateau

    YU WuSheng; MA YaoMing; SUN WeiZhen; WANG Yu

    2009-01-01

    Analysis of daily precipitation samples for stable oxygen isotopes (δ18O) collected at the Shiquanhe and Gêrzê (Gaize,Gertse) stations in the Ngari (Ali) region on the western Tibetan Plateau indicates that air temperature affects the δ18O variations in precipitation at these stations,in summer,Shiquanhe and Gêrzê show strongly similar trends in precipitation δ18O,especially in simultaneous precipitation events.Moreover,both stations experienced low δ18O values in precipitation during the active monsoon period,resulting from the southwest monsoon (the summer phase of the Indian monsoon).However,during the break monsoon period (during the summer rainy season,when the monsoon circulation is disrupted),δ18O values in summer precipitation remain relatively high and local moisture recycling generally controls the moisture sources.Air temperature correlations with δ18O strengthen during the non-monsoon period (January-June,and October-December) due to continental air masses and the westerlies.In addition,evaporation also influences the δ18O variations in precipitation.The observed temporal and spatial variations of δ18O in precipitation on the western Tibetan Plateau and adjacent regions show that the late May and early June-the late August and early September time frame provides an important period for the transportation of moisture from various sources on the Tibetan Plateau,and that the region of the West Kunlun-Tanggula Ranges acts as a significant climatic divide on the Plateau,perhaps for all of western China.

  12. Microscopic multichannel calculation of the molecular dipole degree of freedom in the /sup 18/O nucleus

    Funck, C.; Grund, B.; Langanke, K.

    1989-09-01

    Strong B(E1) transitions have been recently observed between states in the /sup 18/O nucleus which follow roughly the energy sequence of a dimolecular /alpha/+/sup 14/C rotator. These findings have been interpreted by Gai et al. as evidence for a molecular dipole degree of freedom being present in the /sup 18/O nucleus. However, this idea was contradicted by the results of a microscopic multichannel calculation performed by Descouvemont and Baye which was based on elastic /alpha/+/sup 14/C and inelastic /alpha/+/sup 14/C(2/sup +/) many-body cluster wave functions. We have improved this study by performing a microscopic multichannel calculation including additionally a n+/sup 17/O many-body fragmentation in order to enlarge our model space by those shell model components which dominate the structure of the (positive parity) /sup 18/O ground state band. Like Descouvemont and Baye we find a positive parity /alpha/+/sup 14/C molecular band in /sup 18/O and, additionally, a rather strong collectivity in the lowest 1/sup -/, 3/sup -/, and 5/sup -/ states in /sup 18/O. However, since the internal structure is different within these states, the calculated states should not be interpreted as a negative parity /alpha/+/sup 14/C molecular band. In this perspective, the microscopic multichannel calculations do not support the hypothesis of a molecular dipole degree of freedom being present in the /sup 18/O nucleus. (orig.).

  13. Microscopic multichannel calculation of the molecular dipole degree of freedom in the 18O nucleus

    Strong B(E1) transitions have been recently observed between states in the 18O nucleus which follow roughly the energy sequence of a dimolecular α+14C rotator. These findings have been interpreted by Gai et al. as evidence for a molecular dipole degree of freedom being present in the 18O nucleus. However, this idea was contradicted by the results of a microscopic multichannel calculation performed by Descouvemont and Baye which was based on elastic α+14C and inelastic α+14C(2+) many-body cluster wave functions. We have improved this study by performing a microscopic multichannel calculation including additionally a n+17O many-body fragmentation in order to enlarge our model space by those shell model components which dominate the structure of the (positive parity) 18O ground state band. Like Descouvemont and Baye we find a positive parity α+14C molecular band in 18O and, additionally, a rather strong collectivity in the lowest 1-, 3-, and 5- states in 18O. However, since the internal structure is different within these states, the calculated states should not be interpreted as a negative parity α+14C molecular band. In this perspective, the microscopic multichannel calculations do not support the hypothesis of a molecular dipole degree of freedom being present in the 18O nucleus. (orig.)

  14. Routine quality control of recycled target [18O]water by capillary electrophoresis and gas chromatography

    Recycling of [18O]water for [18F]fluoride production can be accomplished with reliable results. We have developed sensitive, robust, and rapid analyses of impurities in [18O]water. Anions were quantitated by capillary electrophoresis and organic residuals were quantitated by gas chromatography using methods with excellent reproducibility and linearity. Kryptofix 222 (K-222) was quantitated by a sensitive LC-MS-MS technique. Isotopic composition was determined by GC-MS with satisfactory accuracy and precision. These methods were employed to evaluate recovered [18O]water purified by a novel electrolysis method. 2-[18F]FDG yields using purified [18O]water with very low levels of impurities are indistinguishable from newly purchased [18O]water. High (> 300 ppm) carbonate concentration reduces the fluoride trapping efficiency of QMA. The analyses of anions, organics, and isotopic enrichment were applied routinely for quality control of [18O]water to predict a satisfactory outcome of 2-[18F]FDG production

  15. Simulation and optimization of stable isotope 18O separation by water vacuum distillation

    In the research, a stable isotope 18O separation column was set up by water vacuum distillation with 20 m packing height and 0.1 m diameter of the column. The self-developed special packing named PAC-18O was packed inside the column. Firstly, a model was created by using the Aspen Plus software, and then the simulation results were validated by test results. Secondly, a group of simulation results were created by Aspen Plus, and the optimal operation conditions were gotten by using the artificial neural network (ANN) and Statistica software. Considering comprehensive factors drawn from column pressure and from withdrawing velocity, conclusions were reached on the study of the impact on the abundance of the isotope 18O. The final results show that the abundance of the isotope 18O increases as column pressure dropping and withdrawing velocity decreasing. Besides, the optimal column pressure and the incidence formula between the abundance of the isotope 18O and withdrawing velocity were gotten. The conclusion is that the method of simulation and optimization can be applied to 18O industrial design and will be popular in traditional distillation process to realize optimization design. (authors)

  16. Synthesis of tungsten oxide (W18O49) nanosheets utilizing EDTA salt by microwave irradiation method

    Research highlights: → We have synthesized tungsten oxide (WO3-δ) nanoparticles by microwave irradiation method for the first time using EDTA as surface modulator. The variation in stoichiometric oxygen content of the annealed samples clearly indicates the role of EDTA in reaction medium. The variation in oxygen content also modified the transparency of the end product confirming the change in optical conductivity. - Abstract: We report the synthesis of crystalline W18O49 with nanosheet like morphology by low cost microwave irradiation method without employing hydrothermal process for the first time. Initially, WO3.H2O was synthesized using ethylenediaminetetraacetic acid (EDTA) as surface modulator. The product was annealed at 600 oC for 6 h in ambient atmosphere in order to obtain anhydrous tungsten oxide W18O49. Powder X-ray diffraction results confirmed the as prepared WO3.H2O to be orthorhombic and W18O49 to be monoclinic phase, respectively. Transmission electron micrographs (TEM) revealed that the W18O49 nanosheets have the average dimensions of the order of 250 nm in length and around 150 nm in width. UV-visible diffusion reflectance spectroscopic (DRS) studies revealed the band gap energies to be 3.28 and 3.47 eV for WO3.H2O and W18O49 samples, respectively. The growth mechanism of two dimensional W18O49 nanosheets is discussed.

  17. Additional evidence for fusion-fission in 32S+24Mg reactions: Division of excitation energy and spin in the fission fragments

    We have measured γ rays in coincidence with 12C fragments from the fission of 56Ni produced with the 32S+24Mg reaction at Elab=140 MeV. These data provide insight into the fission process in this light system by giving information about the energy and spin sharing between the 12C and 44Ti fragments, and the spin alignment of the lighter, 12C fragment. The spin transfer and the nuclear ''temperature'' at scission deduced from this measurement can be related to the compound-nucleus spin and potential energy at scission. The results indicate a statistical decay process consistent with the predictions of the transition-state model employing newer estimates of the spin- and mass-asymmetry-dependent saddle-point energies and corresponding shapes. No evidence is found for the spin alignment of the 12C fragments, contrary to what might be expected for a deep-inelastic scattering origin of the fully energy damped yields

  18. Clustering effects in fusion evaporation reactions with light even-even N=Z nuclei. The 24Mg and 28Si cases

    Morelli, L.; Bruno, M.; D'Agostino, M.; Baiocco, G.; Gulminelli, F.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gramegna, F.; Marchi, T.; Barlini, S.; Bini, M.; Casini, G.; Gelli, N.; Pasquali, G.; Piantelli, S.; Valdrè, S.

    2016-06-01

    In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. The decay of highly excited states of 24Mg is studied in fusion evaporation events completely detected in charge in the reactions 12C+12C and 14N+10B at 95 and 80 MeV incident energy, respectively, and compared to the results of a pure statistical model [3, 4]. Inclusive variables are in general well reproduced by the model. We found clear deviations from the statistical model if we select emission channels involving multiple α particles which are more probable than expected from a purely statistical behavior. Data from 12C+12C reaction have been analyzed in order to study the decay of the Hoyle state of 12C* with two different selections: peripheral binary collisions and 6α decay channel in central events. To continue the investigation on light systems, we have recently measured the 16O+12C reaction at three different beam energies, namely Ebeam = 90, 110 and 130 MeV. Preliminary results are presented.

  19. (d, t) and (d, 3He) reactions on 12C, 16O, 24Mg, and 40Ca at 29 MeV

    The (d,t) and (d,3He) reactions on targets of 12C, 16O, 24Mg,and 40Ca leading to prominent low-lying analog states in the residual nuclei have been studies by measuring differential cross sections and vector analyzing powers. The cross section angular distributions at best exhibit only a weak sensitivity to the transferred angular momentum while the vector analyzing powers are strongly sensitive to the transferred angular momentum and provide a useful signature of the j transfer. Zero-range distorted-wave Born approximation predictions describe the sigma (theta) angular distributions quite well for the lighter targets while they only partially succeed in describing the A/sub y/(theta) for the lighter targets. An improved distorted-wave Born approximation description was obtained for the 40Ca target. Some sensitivity to the choice of optical parameters in the distorted-wave Born approximation analysis, particularly obvious in the A/sub y/(theta) predictions was seen. Values of extracted spectroscopic factors were generally consistent with those reported in other work

  20. Calibration of speleothem δ18O records against hydroclimate instrumental records in Central Brazil

    Moquet, J. S.; Cruz, F. W.; Novello, V. F.; Stríkis, N. M.; Deininger, M.; Karmann, I.; Santos, R. Ventura; Millo, C.; Apaestegui, J.; Guyot, J.-L.; Siffedine, A.; Vuille, M.; Cheng, H.; Edwards, R. L.; Santini, W.

    2016-04-01

    δ18O in speleothems is a powerful proxy for reconstruction of precipitation patterns in tropical and sub-tropical regions. The aim of this study is to calibrate the δ18O record of speleothems against historical precipitation and river discharge data in central Brazil, a region directly influenced by the Southern Atlantic Convergence Zone (SACZ), a major feature of the South American Monsoon System (SAMS). The present work is based on a sub-annual resolution speleothem record covering the last 141 years (the period between the years 1870 and 2011) from a cave in central Brazil. The comparison of this record with instrumental hydroclimate records since 1921 allows defining a strong relationship between precipitation variability and stable oxygen isotope ratios from speleothems. The results from a monitoring program of climatic parameters and isotopic composition of rainfall and cave seepage waters performed in the same cave, show that the rain δ18O variability is dominated by the amount effect in this region, while δ18O drip water remains almost constant over the monitored period (1.5 years). The δ18O of modern calcite, on the other hand, shows clear seasonal variations, with more negative values observed during the rainy season, which implies that other factors also influence the isotopic composition of carbonate. However, the relationship between δ18O of carbonate deposits and rainwater is supported by the results from the comparison between speleothem δ18O records and historical hydroclimate records. A significant correlation between speleothem δ18O and monsoon rainfall variability is observed on sub-decadal time scales, especially for the monsoon period (DJFM and NDJFM), once the rainfall record have been smoothed with a 7-9 years running mean. This study confirms that speleothem δ18O is directly associated with monsoon rainfall variability in central Brazil. The relationship between speleothem δ18O records and hydroclimatic historical records allows

  1. The "Flood of the Century" as Isotopic Fingerprint in Canopy d18O Signatures

    Seibt, U.; Wingate, L.; Berry, J. A.

    2006-12-01

    The d18O composition of water and CO2 exchange at smaller scales (leaf and ecosystem) can be affected by changes in environmental conditions at larger (regional) scales. During a sampling campaign in a beech forest in Germany in August 2002, we encountered such a large scale change when dry sunny weather was followed by a large storm system with heavy rains leading to floods across Europe. During the first, sunny period, bulk leaf water d18O was -1 permil at night and 7 permil at mid-day. Foliage CO2 exchange had positive values of 18O discrimination during photosynthesis (10-30 permil) and nocturnal respiration (11 permil). The second period had frequent rains and mostly diffuse light, with reduced foliage water fluxes but similar carbon fluxes. Canopy vapour d18O decreased at least 2 permil, and leaf water then reflected isotopic exchange with this depleted vapour due to the high humidity. Hence, bulk leaf water was substantially more depleted at night (-8 permil) and showed virtually no evaporative enrichment during the day (-5 permil). Values of 18O discrimination during CO2 exchange were small or even negative for photosynthesis (-2 to 6 permil) but larger for nocturnal respiration (23-39 permil). Model simulations indicated that the small positive foliage isoflux during the day was offset by the negative isoflux at night. As a consequence, the d18O of CO2 in canopy air decreased from -0.3 permil during the sunny period to -3 permil during the wet period. The d18O signatures of canopy water and CO2 thus reflected the transition from local water to the regional regime of depleted water deposited across the area by the storm.

  2. Experimental study of the 18O(d, p)19O reaction and the ANC Method

    The neutron capture rate 18O(n, γ)19O is important for analysis of nucleosynthesis in inhomogeneous Big Bang models and also for models of helium burning in massive red giant stars and AGB stars. Angular distributions of the 18O(d, p)19O reaction were measured at a deuteron energy of 16.3 MeV in NPI in Rez, Czech Republic, with the aim to determine Asymptotic Normalization Coefficients which can then be used for indirect determination of the direct contribution to the 18O(n, γ)19O process. In the experiment, the gas target with 18O isotope of high purity 99.9% was used thus eliminating any contaminating reactions. Reaction products were measured by the set of 8 ΔE-E telescopes consisting of thin and thick silicon surface-barrier detectors. Angular distributions of proton transfers corresponding to 6 levels of 19O up to the 4.1093 MeV excitation energy were determined. The analysis of angular distributions in the angular range from 6 to 64 degree including also the angular distribution of elastically scattered deuterons was carried out by means of ECIS and DWUCK codes. From the determined ANCs the direct contribution to the radiative capture 18O(n, γ)19O was deduced.

  3. Electrochemical zinc insertion into W18O49: Synthesis and characterization of new bronzes

    Divalent zinc ions have been electrochemically inserted into W18O49, producing zinc bronzes. Under our experimental conditions, W18O49 accepts zinc reversibly as a guest up to 0.9 ions per formula. The reaction seems to proceed through the formation of a solid solution in which the W-O framework of the parent oxide is maintained. The location of the Zn2+ ions in the framework of W18O49 has been determined by neutron diffraction on a chemically prepared sample having the composition Zn0.34W18O49. As a main result, we found that Zn prefers to insert in one of the four types of quadrangular tunnels. More precisely, it is displaced from the center to occupy a low coordination site. This result indicates that a significant covalent character exists in the Zn-O bond. - Graphical Abstract: The structure of Zn0.36W18O49 projected along the b-axis

  4. A forward model of cave dripwater δ18O and application to speleothem records

    Speleothem oxygen isotope records in arid regions are typically interpreted as indicators of the total precipitation amount and/or its seasonal balance. Such studies rarely address the potential influence of groundwater mixing processes on δ18O variability of cave dripwater. Here, we develop a model of oxygen isotopes in dripwater, which we compare to water and stalagmite measurements from Cave of the Bells, Arizona. We simulate moisture flux from surface to cave as a two-layer 'leaky-bucket' model. In observations and the model, fed with modern climate data, dripwater δ18O is most comparable to that of winter precipitation. We show that seasonality and duration of the regional summer monsoon affect how much summer precipitation reaches the cave. We employ a Monte Carlo method to specify statistically realistic ranges for input climate variables and produce time series and variance spectra of cave drips. The spectra of our synthetic δ18O series exhibit a high degree of variance at decadal to multidecadal frequencies, despite being driven by synthetic data that includes only a seasonal cycle. This suggests that some background level of variance in speleothem δ18O records could be due to nonclimatic processes, such as subsurface water storage and mixing. Interpreting climatic vs. nonclimatic controls on speleothem δ18O variance could be achieved by replicating records from different caves.

  5. Variations of δ18O in Precipitation along Vapor Transport Paths

    章新平; 刘晶淼; 田立德; 何元庆; 姚檀栋

    2004-01-01

    Three sampling cross sections along the south path starting from the Tropics through the vapor passage in the Yunnan-Guizhou Plateau to the middle-low reaches of the Yangtze River, the north path from West China, via North China, to Japan under the westerlies, and the plateau path from South Asia over the Himalayas to the northern Tibetan Plateau, are set up, based on the IAEA (International Atomic Energy Agency)/WMO global survey network and sampling sites on the Tibetan Plateau. The variations, and the relationship with precipitation and temperature, of the δ18O in precipitation along the three cross sections are analyzed and compared. Along the south path, the seasonal differences of mean δ18O in precipitation are small at the stations located in the Tropics, but increase markedly from Bangkok towards the north, with the δ18O in the rainy season smaller than inthe dry season. The δ18O values in precipitation fluctuate on the whole, which shows that there are different vapor sources. Along the north path, the seasonal differences of the mean δ18O in precipitation for the stations in the west of Zhengzhou are all greater than in the east of Zhengzhou. During the cold half of the year, the mean δ18O in precipitation reaches its minimum at Urumqi with the lowest temperature due to the wide, cold high pressure over Mongolia, then increases gradually with longitude, and remains at roughly the same level at the stations eastward from Zhengzhou. During the warm half of the year, the δ18O values in precipitation are lower in the east than in the west, markedly influenced by the summer monsoon over East Asia. Along the plateau path, the mean δ18O values in precipitation in the rainy season are correspondingly high in the southern parts of the Indian subcontinent, and then decrease gradually with latitude. A sharp depletion of the stable isotopic compositions in precipitation takes place due to the very strong rainout of the stable isotopic compositions in vapor in

  6. Leaching studies of soda-lime-silica glass using deuterium- and 18O-enriched solutions

    With a glass of composition (in mol%) 74 SiO2,16 NaO, 10 CaO, various leaching experiments were conducted, in which besides solutions of normal isotopic composition deuterium- and 18O-enriched solutions were used. The concentration profiles of deuterium, hydrogen, and 18O in the sample were measured with nuclear analyzing techniques. A distinct H/D isotope effect was observed, showing that hydrogen takes part in the rate-determining step of leaching. The measured ratio of 18O uptake to hydrogen uptake during leaching gives evidence for exchange of oxygen between the glas network and water molecules contained in the leached layer. From measurements on the exchange of hydrogen and oxygen between solution and leached layer, a high mobility of water molecules in the leached layer and evidence for condensation of silanol groups was found. (orig.)

  7. French summer droughts since 1326 AD: a reconstruction based on tree ring cellulose δ18O

    Labuhn, I.; Daux, V.; Girardclos, O.; Stievenard, M.; Pierre, M.; Masson-Delmotte, V.

    2015-11-01

    The reconstruction of droughts is essential for the understanding of past drought dynamics, and can help evaluate future drought scenarios in a changing climate. This article presents a reconstruction of summer droughts in France based on annually resolved, absolutely dated chronologies of oxygen isotope ratios (δ18O) in tree ring cellulose from Quercus spp. Samples were taken from living trees and timber wood from historic buildings at two sites: Fontainebleau (48° 23' N, 2° 40' E; 1326-2000 AD) and Angoulême (45° 44' N, 0° 18' E; 1360-2004 AD). Cellulose δ18O from these sites proved to be a good proxy of summer climate, as the trees were sensitive to temperature and moisture availability. However, offsets in average δ18O values between tree cohorts necessitated a correction before joining them to the final chronologies. Using the corrected δ18O chronologies, we developed models based on linear regression to reconstruct drought, expressed by the standardized precipitation evapotranspiration index (SPEI). The significant correlations between the SPEI and cellulose δ18O (r ≈ -0.70), as well as the verification of the models by independent data support the validity of these reconstructions. At both sites, recent decades are characterized by increasing drought. Fontainebleau displays dominantly wetter conditions during earlier centuries, whereas the current drought intensity is not unprecedented in the Angoulême record. While the δ18O chronologies at the two studied sites are highly correlated during the 19th and 20th century, there is a significant decrease in the correlation coefficient between 1550 and 1800 AD, which indicates either a weaker climate sensitivity of the tree ring proxies during this period, or a more heterogeneous climate in the north and the south of France. Future studies of tree ring isotope networks might reveal if the seasonality and spatial patterns of past droughts can explain this decoupling.

  8. French summer droughts since 1326 AD: a reconstruction based on tree ring cellulose δ18O

    I. Labuhn

    2015-11-01

    Full Text Available The reconstruction of droughts is essential for the understanding of past drought dynamics, and can help evaluate future drought scenarios in a changing climate. This article presents a reconstruction of summer droughts in France based on annually resolved, absolutely dated chronologies of oxygen isotope ratios (δ18O in tree ring cellulose from Quercus spp. Samples were taken from living trees and timber wood from historic buildings at two sites: Fontainebleau (48° 23' N, 2° 40' E; 1326–2000 AD and Angoulême (45° 44' N, 0° 18' E; 1360–2004 AD. Cellulose δ18O from these sites proved to be a good proxy of summer climate, as the trees were sensitive to temperature and moisture availability. However, offsets in average δ18O values between tree cohorts necessitated a correction before joining them to the final chronologies. Using the corrected δ18O chronologies, we developed models based on linear regression to reconstruct drought, expressed by the standardized precipitation evapotranspiration index (SPEI. The significant correlations between the SPEI and cellulose δ18O (r ≈ −0.70, as well as the verification of the models by independent data support the validity of these reconstructions. At both sites, recent decades are characterized by increasing drought. Fontainebleau displays dominantly wetter conditions during earlier centuries, whereas the current drought intensity is not unprecedented in the Angoulême record. While the δ18O chronologies at the two studied sites are highly correlated during the 19th and 20th century, there is a significant decrease in the correlation coefficient between 1550 and 1800 AD, which indicates either a weaker climate sensitivity of the tree ring proxies during this period, or a more heterogeneous climate in the north and the south of France. Future studies of tree ring isotope networks might reveal if the seasonality and spatial patterns of past droughts can explain this decoupling.

  9. Millennial-length forward models and pseudoproxies of stalagmite δ18O: an example from NW Scotland

    C. Spötl

    2012-07-01

    Full Text Available The stable oxygen isotope parameter δ18O remains the most widely utilised speleothem proxy for past climate reconstructions. Uncertainty can be introduced into stalagmite δ18O from a number of factors, one of which is the heterogeneity of groundwater flow in karstified aquifers. Here, we present a lumped parameter hydrological model, KarstFor, which is capable of generating monthly simulations of surface water – ground water – stalagmite δ18O for more than thousand-year time periods. Using a variety of climate input series, we use this model for the first time to compare observational with modelled (pseudoproxy stalagmite δ18O series for a site at Assynt, NW Scotland, where our knowledge of δ18O systematics is relatively well understood. The use of forward modelling allows us to quantify the relative contributions of climate, peat and karst hydrology, and disequilibrium effects in stalagmite δ18O, from which we can identify potential stalagmite δ18O responses to climate variability. Comparison of the modelled and actual stalagmite δ18O for two stalagmites from the site demonstrates that, for the period of overlapping growth, the two series do not correlate with one another, but forward modelling demonstrates that this falls within the range explicable by differences in flow routing to the stalagmites. Pseudoproxy δ18O stalagmite series highlight the potential significance of peat hydrology in controlling stalagmite δ18O over the last 1000 yr at this site.

  10. Millennial-length forward models and pseudoproxies of stalagmite δ18O: an example from NW Scotland

    C. Spötl

    2012-03-01

    Full Text Available The stable oxygen isotope parameter δ18O remains the most widely utilised speleothem proxy for past climate reconstructions. Uncertainty can be introduced into stalagmite δ18O from a number of factors, one of which is the heterogeneity of groundwater flow in karstified aquifers. Here, we present a lumped parameter hydrological model, KarstFor, which is capable of generating monthly simulations of surface water – ground water – stalagmite δ18O for more than thousand year time periods. Using a variety of climate input series, we use this model for the first time to compare observational with modelled (pseudoproxy stalagmite δ18O series for a site at Assynt, NW Scotland, where our knowledge of δ18O systematics is relatively well understood. The use of forward modelling allows us to quantify the relative contributions of climate, peat and karst hydrology, and disequilibrium effects in stalagmite δ18O, from which we can identify potential stalagmite δ18O responses to climate variability. Comparison of the modelled and actual stalagmite δ18O for two stalagmites from the site demonstrates that for the period of overlapping growth, the two series do not correlate with one another, but forward modelling demonstrates that this falls within the range explicable by differences in flow routing to the stalagmites. Pseudoproxy δ18O stalagmite series highlight the potential significance of peat hydrology in controlling stalagmite δ18O over the last 1000 years at this site.

  11. Separating Long-Lived Metal Ions from 18F During H2 18O Recovery

    Cyclotron targets for the production of [18F]fluoride usually use a thin metal window to contain the 18O enriched water during irradiation. This window is activated by the proton beam, and undesired radioisotopes can enter the target water. A pre-packaged strong anion exchange resin is commonly used for [18O]-water recovery. A two-column method has been developed which delivers >95% of the [18F]fluoride for radiosynthesis while rejecting >99.9% of the contaminants. (author)

  12. Nuclear microanalysis of 16O and 18O in near-surface regions of solids. Applications

    The best suited nuclear technique for 18O analysis is the direct observation of nuclear reactions. Here, instead of measuring an induced radioactivity, one observes the particles emitted as a result of the O18(p,α)N15 reaction. The α particles which are produced may be detected with surface barrier semiconductor detectors; they present unit detection efficiency and allow one to realize large solid angles of detection, while their energy resolution is excellent. For getting O18/O16 ratios, 16O must also be measured. This is achieved in a similar way, using the O16(d,p)17O reaction

  13. Generalized hyperspheric function method and the pion scattering by nucleus of 18O

    In the framework of the known multiple scattering theory the differential cross section of the 18Q(PI, PI) reaction for the energies 29, 164, 180 and 230 MeV is calculated. The wave functions of the ground state and excited states of the nucleus 18O are found in the minimum approach of generalized hyperspheric function method. The pion-nucleus t sub(PIA) matrix is constructed by solving the Lippman-Schwinger equation on-energy-shell and taken into account the phases of PIN - scattering. Theoretical values of oifferential cross section of the (PI+- - 18O)-reaction under consideration adequately describe experimental data

  14. Coral δ18O stratigraphy from the West Pacific Warm Pool, Palau

    Osborne, M. C.; Dunbar, R. B.; Mucciarone, D. A.; Sanchez-Cabeza, J.

    2009-12-01

    High-resolution paleoenvironmental records obtained from coral cores are powerful tools for assessing pre-instrumental ENSO behavior on interannual to centennial time scales, but the scarcity of such records limits the robust assessment of natural ENSO variability prior to the start of widespread instrumental monitoring. Here we present new δ18O stratigraphies from four cores sampled from two Porites lutea corals collected in the Republic of Palau during December 2008. Palau lies in the West Pacific Warm Pool (WPWP), a region characterized by warm annual sea surface temperatures (SSTs) and intense atmospheric convection. Variations in the expanse of the WPWP are tightly linked to ENSO dynamics. The δ18O composition of coral skeletal material is determined by the δ18O of seawater as well as SST, and the strong positive correlation between SSTs and precipitation in the WPWP region generally exerts an additive effect on coral δ18O. During strong El Niño events, positive δ18O anomalies in coral aragonite should result from increased salinity and decreased SSTs in Palau, whereas negative δ18O anomalies are expected during La Niña conditions. Overall the δ18O variability in our stratigraphies is consistent between all four cores, though we note small discrepancies attributed to uncertainties in cross-correlation, local environmental variation, and potential vital effects. We compare our analyses with available instrumental data and argue that seasonal climate variations in Palau are evident in our coral stratigraphies. Based on this assertion, these data can be used for age model constructions as well as for climate analyses in the time and frequency domains. Our estimates of coral growth rates are ~1.5 cm/yr, yielding ~70 years of record from coral U-1/U-2 and ~25 years from coral U-3/U-4. With continued analyses we expect to provide coral-based climate time series of ~180 yrs in length from core U-2. We also provide evidence that periods of strong ENSO

  15. Excitation Function for the 74Se(18O,p3n) Reaction

    Gates, Jacklyn

    2009-01-01

    The 74Se(18O,p3n)88gNb excitation function was measured and a maximum cross section of 495+-5 mb was observed at and 18O energy of 74.0 MeV. Experimental cross sections were compared to theoretical calculations using the computer code ALICE-91 and the values were found to be in good agreement. The half life of 88gNb was determined to be around 14.56+-0.11 min.

  16. ({sup 18}O,{sup 18}Ne) double charge-exchange with MAGNEX

    Bondí, M.; Cappuzzello, F.; Nicolosi, D.; Tropea, S. [Dipartimento di Fisica e Astrofisica, Universitá degli studi di Catania, Catania, 95100, Italy and Istituto di Fisica Nucleare - Laboratori Nazionali del Sud, Catania, 95100 (Italy); Agodi, C.; Carbone, D.; Cavallaro, M.; Cunsolo, A. [Istituto di Fisica Nucleare - Laboratori Nazionali del Sud, Catania, 95100 (Italy); De Napoli, M.; Foti, A. [Istituto di Fisica Nucleare - Sezione di Catania, Catania, 95100 (Italy)

    2014-05-09

    An experimental study concerning Double Gamow-Teller (DGT) modes in ({sup 18}O,{sup 18}Ne) Double Charge-Exchange reactions has been very recently performed at INFN-LNS laboratory in Catania. The experiment was performed using a {sup 40}Ca solid target and a {sup 18}O Cyclotron beam at 270 MeV incident energy. Charged ejectiles produced in the reaction were momentum analyzed and identified by MAGNEX spectrometer at very forward angles. Preliminary results are presented in the present paper.

  17. Evidence of Suess solar-cycle bursts in Holocene speleothem d18O records

    Knudsen, Mads Faurschou; Jacobsen, B. H.; Riisager, Peter;

    2012-01-01

    subtropical speleothem δ18O records, which allows a strong test of the link between solar activity, monsoon activity (or intensity), and the hydrological cycle. This is possible because the speleothem δ18O records mainly reflect changes in local rainfall composition, which is controlled by changes in total...... driving centennial-scale changes in the hydrological cycle in the subtropics during the Holocene.......Several studies indicate that changes in solar activity may have driven Holocene subtropical monsoon variability on decadal and centennial timescales, but the strength and nature of this link remains debated. In this study, we combine a recent mapping of the Holocene solar-cycle activity with four...

  18. High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm−1: Part II—Analysis and theoretical modeling of the 12C18O2, 13C18O2 and 16O13C18O spectra

    More than 19000 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990 cm−1 (1.71–1.43 μm). The line positions were determined with accuracy better than 1×10−3 cm−1 while the absolute line intensities are reported with an uncertainty better than 10%. This second report is devoted to the analysis of the bands of three multiply substituted isotopologues: 12C18O2, 13C18O2 and 16O13C18O (828, 838 and 638 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 2870, 538 and 1375 transitions belonging to 59, 11 and 15 bands were rovibrationnally assigned for 828, 838 and 638, respectively. For comparison, only 11 bands were previously measured by Fourier Transform spectroscopy in the region, for the 828 species. All the identified bands correspond to a ΔP=9 variation of the polyad number (P=2V1+V2+3V3, where Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 81 bands from a fit of the measured line positions. A few resonance perturbations were identified. In particular, the 31113 and 51106 states of 638 belonging to different polyads (P=10 and P=11, respectively) are anharmonically coupled. Using the large set of newly measured line positions and those collected from the literature, the global modeling of the line positions within the effective Hamiltonian approach was performed and a new set of Hamiltonian parameters was obtained for each of the three considered isopotologues. Using a similar approach, the global fits of the obtained intensity values of the ΔP=9 series of transitions were used to derive the corresponding ΔP=9 effective dipole moment parameters of the three considered isotopologues. The obtained results will help to improve the quality

  19. Thermonuclear reaction rate of 18O(p,gamma)19F

    Buckner, M Q; Cesaratto, J M; Howard, C; Clegg, T B; Champagne, A E; Daigle, S

    2012-01-01

    For stars between 0.8-8.0 solar masses, nucleosynthesis enters its final phase during the asymptotic giant branch (AGB) stage. During this evolutionary period, grain condensation occurs in the stellar atmosphere, and the star experiences significant mass loss. The production of presolar grains can often be attributed to this unique stellar environment. A subset of presolar oxide grains features dramatic 18O depletion that cannot be explained by the standard AGB star burning stages and dredge-up models. An extra mixing process, referred to as "cool bottom processing" (CBP), was proposed for low-mass AGB stars. The 18O depletion observed within certain stellar environments and within presolar grain samples may result from the 18O+p processes during CBP. We report here on a study of the 18O(p,gamma)19F reaction at low energies. Based on our new results, we found that the resonance at Er = 95 keV (lab) has a negligible affect on the reaction rate at the temperatures associated with CBP. We also determined that th...

  20. Fission fragment angular distribution measurements in 18O+194Pt reaction

    Fission fragment angular distributions were measured for 18O + 194Pt in energy range 78.2 - 87.3 MeV. The normal nature of angular anisotropy suggests that the reaction proceeded through true CN formation. The present results are consistent with result obtained from fission fragment mass distribution measurements carried out for reaction using other isotopes of platinum

  1. 18O and 226Ra in the Minjiang River estuary, China and their hydrological implications

    Liu, Huatai; Guo, Zhanrong; Gao, Aiguo; Yuan, Xiaojie; Zhang, Bin

    2016-05-01

    In this work, the 2H, 18O and 226Ra values in groundwater and surface water in the Minjiang River estuary were investigated in the dry and wet seasons. The δ18O values in the dry season were always higher than those in the wet season in both groundwater and surface water because of the presence of evaporation in the water cycle process. During the dry season, the δ18O values in groundwater on the southern bank of the Minjiang River are much higher than those on the northern bank because evaporation is more intense in the farmland of the southern bank than in the urbanized northern bank. The δ18O values in the estuarine water exhibit a good positive correlation with salinity, with a coefficient of 0.96 (p = 0.05) in both seasons. The 226Ra activities in the estuarine water increase with increasing salinity because of desorption from riverine suspended particles. The 226Ra activity reaches a peak value at a salinity of 20.5. Based on a three-endmember model, the average proportions of the estuarine water are calculated to be 0.02 for groundwater, 0.39 for river water and 0.59 for seawater. From this mixing ratio, the groundwater discharge into the estuary is estimated to be 9.31 × 106 m3 d-1 in the wet season.

  2. Reef coral δ18O thermometer in Hainan island waters, south China sea

    An 18-year-long (1981-1998) study was conducted in Hainan Island waters (22 degree 22'N, 110 degree 39'E) to determine the relationship between δ18O in skeletal aragonite carbonate and sea surface temperature (SST) in porites lutea of reef-building corals. δ18O values in skeletal aragonite carbonate were measured by means of mass spectrometry. Coral samples grew at 5 m depth at Longwan Bay. Monthly measurements of the SST from 1960 to 1998 were taken at Qinglan Bay adjacent to the place of the collected samples. The thermometer shows that SST = -4.16 δ18OPDB + 4.9 (r = 0.80) and dδ18O/dT = -0.24 per mil/degree C. The δ18O thermometer is strongly influenced by the rainfall and runoff. Using the thermometer, the SST in the past hundred years with monthly resolution will be reconstructed and the climatic change in the northern area of South China Sea will be hind cast

  3. A foraminiferal δ(18)O record covering the last 2,200 years.

    Taricco, Carla; Alessio, Silvia; Rubinetti, Sara; Vivaldo, Gianna; Mancuso, Salvatore

    2016-01-01

    Thanks to the precise core dating and the high sedimentation rate of the drilling site (Gallipoli Terrace, Ionian Sea) we were able to measure a foraminiferal δ(18)O series covering the last 2,200 years with a time resolution shorter than 4 years. In order to support the quality of this data-set we link the δ(18)O values measured in the foraminifera shells to temperature and salinity measurements available for the last thirty years covered by the core. Moreover, we describe in detail the dating procedures based on the presence of volcanic markers along the core and on the measurement of (210)Pb and (137)Cs activity in the most recent sediment layers. The high time resolution allows for detecting a δ(18)O decennial-scale oscillation, together with centennial and multicentennial components. Due to the dependence of foraminiferal δ(18)O on environmental conditions, these oscillations can provide information about temperature and salinity variations in past millennia. The strategic location of the drilling area makes this record a unique tool for climate and oceanographic studies of the Central Mediterranean. PMID:27328303

  4. Investigating the past and recent δ18O-accumulation relationship seen in Greenland ice cores

    D. Dahl-Jensen

    2012-12-01

    Full Text Available Decadal means of δ18O and accumulation rates from 52 ice core locations in Greenland are presented. The accumulation rates are derived from annual layers determined in the δ18O curve. Investigation of the δ18O-accumulation relationship across the ice divide reveals a significant Foehn effect with anticorrelation of δ18O and accumulation rate on the lee side of the divide in Southern Greenland, while no effect is seen in Central Greenland. Furthermore, the sensitivity of accumulation rate to changes in temperature is found to be smaller in Northern Greenland than in the central and southern parts. Four records in the data set contain sufficient recent data that the period of observed temperature rise from the 1990s and onwards can be investigated. All four records are from locations close to the ice divide in Northern Greenland and while three of them show increased temperatures, no conclusive statement can be made about the accumulation rate from these data.

  5. Fusion Reactions of ~(16)O+~(76)Ge and ~(18)O+~(74)Ge Near Coulomb Barrier

    2011-01-01

    The fusion excitation functions of 16O+76Ge and 18O+74Ge at near-barrier region are measured, to research the positive Q-2n effect on the fusion reaction. The properties of the lower excited states are similar for the two targets. For neutron transfer channels,

  6. Permo-Pennsylvanian palaeotemperatures from Fe-Oxide and phyllosilicate δ18O values

    Tabor, Neil J.

    2007-01-01

    The oxygen isotope composition of fossil roots that have been permineralized by hematite are presented from eight different stratigraphic levels spanning the Upper Pennsylvanian and Lower Permian strata of north-central Texas. Hematite δ18O values range from - 0.4% to 3.7%. The most negative δ18O values occur in the upper Pennsylvanian strata, and there is a progressive trend toward more positive δ18O values upward through the lower Permian strata. This stratigraphic pattern is similar in magnitude and style to δ18O values reported for penecontemporaneous authigenic palaeosol phyllosilicates and calcites, suggesting that all three minerals record similar paragenetic histories that are probably attributed to temporal palaeoenvironmental changes across the Late Pennsylvanian and Early Permian landscapes. Palaeotemperature estimates based on paired δ18O values between penecontemporaneous hematite and phyllosilicate samples suggest these minerals co-precipitated at relatively low temperatures that are consistent with a supergene origin in a low-latitude soil-forming environment. Hematite-phyllosilicate δ18O pairs indicate (1) relatively low soil temperatures (˜ 24 ± 3 °C) during deposition of the upper Pennsylvanian strata followed by (2) a considerable rise in soil temperatures (˜ 35-37 ± 3 °C) during deposition of the lowermost Permian strata. Significantly, δD and δ18O values of contemporaneous phyllosilicates provide single mineral palaeotemperature estimates that are analytically indistinguishable from temperature estimates based on hematite-phyllosilicate oxygen isotope pairs. The results between the two temperature-proxy methods suggest that the inferred large temperature change across the Upper Pennsylvanian-Lower Permian boundary might be taken seriously. If real, such a significant climate change would have undoubtedly had far-reaching ecological effects within this region of Pangaea. Notably, there are important lithological and palaeobotanical

  7. Evidence for a universal pathway of abscisic acid biosynthesis in higher plants from sup 18 O incorporation patterns

    Zeevaart, J.A.D.; Heath, T.G.; Gage, D.A. (Michigan State University, East Lansing (USA))

    1989-12-01

    Previous labeling studies of abscisic acid (ABA) with {sup 18}O{sub 2} have been mainly conducted with water-stressed leaves. In this study, {sup 18}O incorporation into ABA of stressed leaves of various species was compared with {sup 18}O labeling of ABA of turgid leaves and of fruit tissue in different stages of ripening. In stressed leaves of all six species investigated, avocado (Persea americana), barley (Hordeum vulgare), bean (Phaseolus vulgaris), cocklebur (Xanthium strumarium), spinach (Spinacia oleracea), and tobacco (Nicotiana tabacum), {sup 18}O was most abundant in the carboxyl group, whereas incorporation of a second and third {sup 18}O in the oxygen atoms on the ring of ABA was much less prominent after 24 h in {sup 18}O{sub 2}. ABA from turgid bean leaves showed significant {sup 18}O incorporation, again with highest {sup 18}O enrichment in the carboxyl group. On the basis of {sup 18}O-labeling patterns observed in ABA from different tissues it is concluded that, despite variations in precusor pool sizes and intermediate turnover rates, there is a universal pathway of ABA biosynthesis in higher plants which involves cleavage of a larger precursor molecule, presumably an oxygenated carotenoid.

  8. Evidence for a universal pathway of abscisic acid biosynthesis in higher plants from 18O incorporation patterns

    Previous labeling studies of abscisic acid (ABA) with 18O2 have been mainly conducted with water-stressed leaves. In this study, 18O incorporation into ABA of stressed leaves of various species was compared with 18O labeling of ABA of turgid leaves and of fruit tissue in different stages of ripening. In stressed leaves of all six species investigated, avocado (Persea americana), barley (Hordeum vulgare), bean (Phaseolus vulgaris), cocklebur (Xanthium strumarium), spinach (Spinacia oleracea), and tobacco (Nicotiana tabacum), 18O was most abundant in the carboxyl group, whereas incorporation of a second and third 18O in the oxygen atoms on the ring of ABA was much less prominent after 24 h in 18O2. ABA from turgid bean leaves showed significant 18O incorporation, again with highest 18O enrichment in the carboxyl group. On the basis of 18O-labeling patterns observed in ABA from different tissues it is concluded that, despite variations in precusor pool sizes and intermediate turnover rates, there is a universal pathway of ABA biosynthesis in higher plants which involves cleavage of a larger precursor molecule, presumably an oxygenated carotenoid

  9. Late Holocene hydroclimate change inferred from δ18O of lake sediments, Lost River Range, Idaho

    Krueger, C. R.; Finney, B. P.; Shapley, M.

    2012-12-01

    High-resolution paleohydrological records are needed to assess the frequency and magnitude of past droughts in Idaho and the northern Rocky Mountain region, but are scarce in this semi-arid region. Sediments from Lost Keys Pond (LKP) can be used to reconstruct hydroclimate. LKP is closed to surface outflow and is therefore sensitive to precipitation minus evaporation; surface water is enriched in δ18O compared to the local meteoric waters. In summer 2011 several sediment cores were collected from LKP using a square rod piston corer; the focus of this analysis is an 82-cm Bolivia core. This core contains thinly banded to laminated, authigenic carbonate mud, a recorder of lake δ18O at the time of deposition. This core was sampled for δ18O and /δ13C at 0.5 cm intervals, and the <20 um fraction was isolated to avoid any detrital carbonate. Based on the current age model, sampling at this interval records sub-decadal (5-10 year) hydroclimate variability. The δ18O signal recovered has 5‰ variability over the length of the record, including several major fluctuations in last 1,000 years. During this period, several major dry and wet periods have been recorded occurring over multidecadal timescales, with a trend toward increasing aridity. The δ18O and δ13C records in the lowest decimeter are divergent and mirror each other, above this interval isotopic records have strong covariance. This pattern may be indicative of a change from surface outflow to no surface outflow conditions. The age model is being refined to better assess how this record correlates with other regional records, and ultimately improve our understanding of past atmospheric circulation.

  10. 13C-18O bonding (Δ47) in deep-sea corals: a calibration study

    Kimball, J. B.; Tripati, A.; Dunbar, R. B.; Eagle, R.

    2013-12-01

    Deep-sea corals are a potentially valuable archive of temperature in intermediate and deep waters, regions for which a paucity of temperature data exists. These archives could give valuable insight into the natural variability of areas of the ocean that play an active role in large-scale climate dynamics. Due to significant 'vital effects' (i.e., non-equilibrium mineral compositions) in δ18O, however, deep-sea coral have been challenging to develop as a paleotemperature proxy. Clumped-isotope paleothermometry is a new method that may circumvent some of the known complications with δ18O paleotemperature analysis in deep-sea coral. This geothermometer is based on the ordering of heavy 13C-18O ';clumps' in carbonate minerals. Initial calibration studies have shown that the method is independent from the solution chemistry of the precipitating fluids as well as 'vital effects' in deep-sea corals and other types of carbonates. Some kinetic effects have been observed in tropical corals and speleothems. Here we report new data in order to further develop clumped isotopes as a paleothermometer in deep-sea corals as well as to investigate taxon-specific effects. 13C-18O bond ordering was analyzed in live-collected scleractinian (Enallopsammia sp.) and gorgonian (Isididae and Coralliidae) deep-sea corals. We determined mass 47 anomalies in samples (Δ47), which refers to the parts per thousand excess of 13C-18O-16O in CO2 produced on acid digestion of a sample, relative to the amount predicted to be present if isotopes were randomly distributed amongst all CO2 isotopologues. Measured Δ47 values were compared to in situ temperatures and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects.

  11. Modeling the climatic implications of the Guliya δ18O record during the past 130 ka

    X. Zhou

    2012-05-01

    Full Text Available Using an intermediate-complexity UVic Earth System Climate Model (UVic Model, the geographical and seasonal implications and an indicative sense of the historical climate found in the δ18O record of the Guliya ice core (hereinafter, the Guliya δ18O are investigated under time-dependent orbital forcing with an acceleration factor of 100 over the past 130 ka. The results reveal that the simulated late-summer (August–September Guliya surface air temperature (SAT reproduces the 23-ka precession and 43-ka obliquity cycles in the Guliya δ18O. Furthermore, the Guliya δ18O is significantly correlated with the SAT over the Northern Hemisphere (NH, which suggests the Guliya δ18O is an indicator of the late-summer SAT in the NH. Corresponding to the warm and cold phases of the precession cycle in the Guliya temperature, there are two anomalous patterns in the SAT and sea surface temperature (SST fields. The first anomalous pattern shows an increase in the SAT (SST toward the Arctic, possibly associated with the joint effect of the precession and obliquity cycles, and the second anomalous pattern shows an increase in the SAT (SST toward the equator, possibly due to the influence of the precession cycle. Additionally, the summer (winter Guliya and NH temperatures are higher (lower in the warm phases of Guliya late-summer SAT than in the cold phases. Furthermore, the Guliya SAT is closely related to the North Atlantic SST, in which the Guliya precipitation may act as a "bridge" linking the Guliya SAT and the North Atlantic SST.

  12. Study of the angular correlations of light charged particles for the reaction {sup 35}CI (260 MeV) + {sup 24}Mg; Etude des correlations angulaires de particules legeres chargees dans la reaction {sup 35}CI (260 MeV) + {sup 24}Mg

    Mahboub, D.

    1996-10-30

    This work is focussed on the investigation of deformed nuclei. The asymmetric fusion-fission of light heavy-ions (A {<=}60) with a high excitation energy (T {approx} 4 MeV) had lead to a large deformation of the compound nucleus at the scission point. The angular correlations between light particles (LP) and their emitting fragments has been used to probe the deformation of nucleus. Exclusive measurements were performed for the {sup 35}Cl (260 MeV) + {sup 24}Mg system leading to the {sup 59}Cu compound nucleus (CN). The comparison between the energy spectra of LP`s and a statistical calculation carried out by a Monte-Carlo code CASCADE has suggested a deformation of 1.3 (for an oblate shape) of the CN within the frame work of fusion-evaporation process. The source velocity spectrum of {alpha} particles and angular correlations of LP`s have showed that pre-scission and pre-equilibrium emissions are negligible in the present reaction. Finally the confrontation of the data with the statistical code GEMINI has pointed out the sequential emission character of the LP`s from the fission fragments. (author). 175 refs.

  13. The multiPrep - a new on line system for combined isotopic analysis of deuterium and 18O of water as well as 13C and 18O in individual carbonate samples

    Classical dual inlet IRMS techniques for the measurement of 18O in water, deuterium in water and 13C and 18O in carbonates have, until now involved the use of analysis dedicated on-line preparation systems or a mix of offline preparation followed by automated analysis

  14. Coherency of European speleothem δ18O records linked to North Atlantic ocean circulation

    Deininger, Michael; McDermott, Frank

    2016-04-01

    Speleothem δ18O records can provide valuable information about past continental environmental and climatic conditions. In recent decades a European speleothem network has been assembled that allows us to reconstruct past climate variability in both space and time. In particular climate variability during the Holocene was investigated by these studies. The Holocene is thus an ideal period to apply sophisticated statistical methods to derive spatio-temporal pattern of common climate variability in the European speleothem record. Here we evaluate a compilation of 10 speleothem δ18O records covering the last 4.5 ka for their shared variability. The selected speleothem δ18O records must satisfy certain quality criteria to be included: (i) a robust age model; (ii) a temporal intra-sampling resolution of smaller than 30 years; and (iii) the record should be published. A Monte Carlo based Principal Component Analysis (MC-PCA) that accounts for uncertainties in individual speleothem age models and for the different and varying temporal resolutions of each speleothem δ18O record was used for this purpose. Our MC-PCA approach allows not only the identification of temporally coherent changes in δ18O records, but it also facilitates their depiction and evaluation spatially. The compiled speleothem δ18O records span almost the entire European continent (with the exception of the circum-Mediterranean region) ranging from the western Margin of the European continent (stalagmite CC-3, Ireland) to Northern Turkey (SO-1) and from Northern Italy (CC-26) to Norway (FM-3). For the MC-PCA analysis, the 4.5 ka period was sub-divided into eight 1 ka long time windows that overlap the subsequent time window by 500 years to allow a comparison of the temporal evolution of the common signal. In this study we only interpreted the 1st principal component (PC) that depict the spatio-temporal pattern with the highest explained variability of all speleothem δ18O records. Our MC-PCA results

  15. French summer droughts since 1326 CE: a reconstruction based on tree ring cellulose δ18O

    Labuhn, Inga; Daux, Valérie; Girardclos, Olivier; Stievenard, Michel; Pierre, Monique; Masson-Delmotte, Valérie

    2016-05-01

    The reconstruction of droughts is essential for the understanding of past drought dynamics and can help evaluate future drought scenarios in a changing climate. This article presents a reconstruction of summer droughts in France based on annually resolved, absolutely dated chronologies of oxygen isotope ratios (δ18O) in tree ring cellulose from Quercus spp. Samples were taken from living trees and timber wood from historic buildings at two sites: Fontainebleau (48°23' N, 2°40' E; 1326-2000 CE) and Angoulême (45°44' N, 0°18' E; 1360-2004 CE). Cellulose δ18O from these sites proved to be a good proxy of summer climate, as the trees were sensitive to temperature and moisture availability. However, offsets in average δ18O values between tree cohorts necessitated a correction before joining them to the final chronologies. Using the corrected δ18O chronologies, we developed models based on linear regression to reconstruct drought, expressed by the standardized precipitation evapotranspiration index (SPEI). The significant correlations between the SPEI and cellulose δ18O (r ≈ -0.70), as well as the verification of the models by independent data support the validity of these reconstructions. At both sites, recent decades are characterized by increasing drought. Fontainebleau displays dominantly wetter conditions during earlier centuries, whereas the current drought intensity is not unprecedented in the Angoulême record. While the δ18O chronologies at the two studied sites are highly correlated during the 19th and 20th centuries, there is a significant decrease in the correlation coefficient between 1600 and 1800 CE, which indicates either a weaker climate sensitivity of the tree ring proxies during this period, or a more heterogeneous climate in the north and the south of France. Future studies of tree ring isotope networks might reveal if the seasonality and spatial patterns of past droughts can explain this decoupling. A regional drought reconstruction

  16. δ18O comparisons of coral cores in the western tropical Pacific, Palau

    Johnston, E.; Osborne, M. C.

    2010-12-01

    Certain corals secrete calcium carbonate exoskeletons that can record changes in ocean water temperature and salinity when tested for δ18O by mass spectrometry. Records from these corals provide insight into the chemistry of the seas for times when instrumental records were not available. The composition of δ18O in coral calcium carbonate reflects both the temperature of the water and the δ18O composition of the water the corals were growing in. Calcium carbonate that is relatively high in 18O indicates that the corals were growing in ocean water with cooler temperatures and/ or higher salinity due to decreased precipitation or increased evaporation. On the other hand, a decrease in 18O indicates warmer and/ or less saline waters. Broadly speaking, changes in evaporation and precipitation are linked to El Niño/La Niña and Southern Oscillation cycles (ENSO) in the tropical Pacific. Palau, an archipelago in the western tropical Pacific, is greatly affected during El Niño years by abnormally cool waters and decreased rainfall. The opposite conditions are common during La Niña. In 2000, two coral cores were collected in a lagoon in Ngaragebal, Palau by Japanese researchers (7°24.30.3” N, 134°26’53.1”E; Iijima et. Al, 2003). Later, in 2008, two different cores of the same species were collected in the same lagoon in Ngaragebal, Palau by a separate group of scientists (7°24.386”N, 134°26.115”E). Here I compare overlapping δ18O data from the two research groups to create a correlation coefficient which will reveal how closely related the data sets are. Due to it’s location inside a lagoon, unlike other coral collection sites which may be more exposed to open ocean conditions, data from Ngaragebal could be capturing a local signal. However, if data from multiple sites around Palau are similar, this gives us confidence in our interpretations of long term trends. Also, by comparing Ngaragebel data from two different research groups, we can test for

  17. Neutron distribution and yield produced by 50 MeV/u 18O-ion on thick targets

    1999-01-01

    Neutron energy, fluence rate, angular distributions anddose equivalent rate distributions around the thick Be, Cu,Au targets bombarded by 50 MeV/u 18O-ion were measured usinga threshold detector activation method. At the same time, theneutron yields of 18O-ion and the neutron emission rates inthe forward direction were obtained approximately.

  18. Cross sections of barium isotopes in the interaction of 60 MeV/nucleon 18O with 238U

    Barium isotopes were produced by 60 MeV/u 18O ion bombardment of natural uranium via 238U (18O, X) reactions. Ba sources were prepared by radiochemical separation, and measured by a HPGe detector. The cumulative cross sections were obtained by analysis of measured time sequence γ-ray spectra. A double peak phenomenon in Ba isotope distribution was observed. (author)

  19. Influence of Carbonic Anhydrase Activity in Terrestrial Vegetation on the 18O Content of Atmospheric CO2

    Gillon, Jim; Yakir, Dan

    2001-03-01

    The oxygen-18 (18O) content of atmospheric carbon dioxide (CO2) is an important indicator of CO2 uptake on land. It has generally been assumed that during photosynthesis, oxygen in CO2 reaches isotopic equilibrium with oxygen in 18O-enriched water in leaves. We show, however, large differences in the activity of carbonic anhydrase (which catalyzes CO2 hydration and 18O exchange in leaves) among major plant groups that cause variations in the extent of 18O equilibrium (θeq). A clear distinction in θeq between C3 trees and shrubs, and C4 grasses makes atmospheric C18OO a potentially sensitive indicator to changes in C3 and C4 productivity. We estimate a global mean θeq value of ~0.8, which reasonably reconciles inconsistencies between 18O budgets of atmospheric O2 (Dole effect) and CO2.

  20. Application of stable isotopes (18O, D) to study the provenience of mineral waters from some locations of Romania

    The isotopic study (18O, D) of mineral waters from some locations (Bucovina, Covasna, Tusnad and Someseni) in Romania was carried out in a tentative to identify their origin. The investigations of waters from Bucovina, Covasna and Someseni (Springs No.1, 2, and 15) indicates the meteoric provenience, having the deuterium content of meteoric water, but shifted to higher 18O content. This 18O shift is the result of isotopic exchange of the water oxi gen with the rocks oxygen in its trajectory to discharge. The Spring No. 8 waters from Someseni Spa and Tusnad waters present the water isotopic content of mixed deep water with shallower meteoric water having heavier isotopic (D, 18O) content. The Spring No.3 waters from Someseni Spa present the springtime isotopic pulse, like a Becas brook, with water depletion in D and 18O isotopes proving pollution with surrounding snow water. (authors)

  1. ENSO flavors in a tree-ring δ18O record of Tectona grandis from Indonesia

    Schollaen, K.; Karamperidou, C.; Krusic, P.; Cook, E.; Helle, G.

    2015-10-01

    Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900-2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics, as well as the potential of palaeoclimate proxy records from appropriately selected tropical regions for reconstructing past variability of. ENSO flavors.

  2. ENSO flavors in a tree-ring δ18O record of Tectona grandis from Indonesia

    K. Schollaen

    2014-10-01

    Full Text Available Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño–Southern Oscillation (ENSO events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007 of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics.

  3. Analysis of a run-off hydrograph by means of natural 18O

    A deviation of the oxygen isotopic composition in precipitation from the average 18O/l6O in groundwater can be considered to indicate the presence of some 18O tracer. In this way the precipitation component in the discharge of a catchment area can be established. In a small drainage basin (650 ha) the direct peak run-off in the stream channels from a rain storm is shown to consist of rainwater above a slowly increasing base flow. The fast run-off contains two components: (1) overland flow with a time constant of 1 h; (2) a moderately declining component (time constant of 12 h) probably caused by the release of bank storage. From a complex storm it is shown that 87% infiltrates into the soil and the remaining 13% is drained within a few days. (author)

  4. Validation of alpha-Q-value systematics: response of 18O + 159Tb system

    In order to look for the projectile structure effect on ICF reactions in the present experiments the excitation functions of radio-nuclides populated during the interactions of 18O+159Tb at energies ≈ 4-7 MeV/A have been measured. The present data will be compared with 16O+159Tb data, to draw some conclusion about alpha-Q-value systematics, as 18O has more negative Qα-value than 16O. In these experiments the activation technique has been used. The targets of 159Tb of thickness ≈ 1.5 - 2.0 mg/cm2 and Al-catchers (≈1.5-2.5 mg/cm2) were prepared by rolling method

  5. Synthesis and applications of 18O standards for nuclear reaction analysis

    A new method to synthesize 18O standard samples to be used in nuclear reaction analyses is proposed and investigated. This method consists of obtaining a Si18O2 film on a Si substrate using a natural abundance SiO2 film as a passivation layer to prevent the isotopically enriched film to be exposed to the atmosphere and possibly degraded by it. For that, sequential oxidation steps are performed followed by a controlled etching in aqueous hydrofluoric acid. Details of these steps are discussed as well as the stability of the synthesized samples. Applications using these standard samples in the field of alternative semiconductors to Si (SiC and Ge), used in micro and nanoelectronics are also presented

  6. Temporal and spatial distributions of δ18O and δ2H in precipitation in Romania

    Nagavciuc, Viorica; Bădăluță, Carmen-Andreea; Perșoiu, Aurel

    2015-04-01

    Stable isotope ratios of meteoric water have an important role in climatic, paleoclimatic, hydrological and meteorological studies. While such data are available from most of Europe, so far, in Romania (East Central Europe), no systematic study of the stable isotopic composition of precipitation exists. In this context, the aim of this study is to analyze the isotopic composition of rainwater, its temporal and spatial distribution, the identification of the main factors influencing these variations and the creation of the first map of spatial distribution of stable isotopes in precipitation in Romania. Between March 2012 and March 2014 we have collected monthly samples from 22 stations in Romania, which were subsequently analyzed for their δ18O and δ2H at the Stable Isotopes Laboratory, Stefan cel Mare University, Suceava, Romania. Precipitation in W and NW Romania plot along the GMWL, while those in the East are slightly below it, on an evaporative trend. The LMWL for Romania is defined as δ2H=7,27*δ18O + 6,92. The W-E gradient in the distribution of δ18O and δ2H are less marked than the N-S ones, with local influences dominating in areas of strong evaporation (intramountain basins, rain-shadow areas etc). In SW, and especially in autumn and winter, Meditteranean cyclones carry moisture from the Eastern Mediterranean, the δ18O and δ2H values in precipitation in the area plotting between the GMWL and the Eastern Mediterranean Meteoric Water Line. The isotopic composition of rainwater in Romania correlates well with air temperature, and is influenced to a lesser extent by other factors such as the amount of precipitation, topography configuration, the effect of continentalism and season of the year.

  7. Regional groundwater flow in the Atikokan Research Area : simulation of 18O and 3H distributions

    AECL is investigating a concept for disposing of nuclear fuel waste deep in plutonic rock of the Canadian Shield. As part of this investigation, we have performed a model simulation of regional groundwater flow in the Atikokan Research Area, a fractured plutonic rock environment of the Canadian Shield, and used the distribution of oxygen-18 (18O) and tritium (3H) in groundwater to test the model. At the first stage of model calibration, groundwater flow was simulated using a three-dimensional finite-element code, MOTIF, in conjunction with a conceptual framework model derived from field geological, geophysical and hydrogeological data. Hydraulic parameters (permeability and porosity) were systematically varied until simulated recharge rates to the water table compared favourably with estimated recharge rates based on stream flow analysis. At the second stage, vertical average linear groundwater velocities from the first stage of the calibration process were combined with conceptualized one-dimensional models of the system to generate depth concentration profiles of 18O and 3H. Recharge-, midline-and discharge area models of both the fracture zones and the rock mass were employed. The simulated profiles formed 'envelopes' around all field 18O and 3H data, indicating that the calibrated velocities used in the model are reasonable. The models demonstrate that the scatter of δ18O and 3H field data from the Atikokan Research Area is consistent with the groundwater flow model predictions and can be explained by the complexity arising from different hydraulic regimes (recharge, midline, discharge) and hydrogeologic environments (fracture zones, rock mass) of the regional flow system. 50 refs., 14 figs., 3 tabs

  8. Temporal and Spatial Variations of δ18O along the Main Stem of Yangtze River, China

    The Yangtze River is the largest river in China, and the third longest in the world. Data on δ2H and δ18O isotopes in the river water provide a very useful tool for interpretation of hydrological processes and hydrological cycles related to climate change and anthropogenic activities in a large scale river basin. Since 2003, 170 water samples have been recovered from the first water campaign and regular samples over one year from four stations have been analyzed for δ2H and δ18O composition. From upstream to downstream, the isotopic composition of 2H and 18O gradually increase. The trendline of the first campaign is situated in the middle of the LMWL and the trendline of isotopic δ2H and δ18O for one year sampling at four regular stations is in good accordance with the LMWL. Water inflow from tributaries joining the main stem of Yangtze River are one of the main reasons for spatial isotopic variations in the river's water. Results revealed that temporal and spatial variations in oxygen and hydrogen isotopes of water samples along the main stem of the Yangtze River are strongly driven by the isotope patterns in regional precipitation. Secondary signals deriving from the influx of evaporatively enriched waters from several major lakes or reservoirs along the system are also apparent. The peak of river water isotopic temporal variations corresponds well to the boundary marking the beginning or end of annual flooding periods at- site. The peaks and valleys of river water temporal isotopic variations may be a good indicator to mark the split in river water between surface and groundwater water influences at a given location for a water year. (author)

  9. Degradation of DNA by iron-bleomycin: mechanistic implications of product 18O incorporation

    Interaction of d(CGCGCG) with Bleomycin (BLM), activated either with Fe(III) and H2O2 or Fe(II), O2 and one electron, results in production of cytosine and a modified oligonucleotide strand (1). Reduction of 1 with NaBD4 followed by enzymatic digestion, derivatization, and GC-MS permits the identification of 2-deoxypentitols-1,4-d2 as their tetra-trimethylsilyl (TMS) derivatives. Similar products have also been isolated from calf thymus DNA and poly(dG-dC). These results provide unequivocal evidence for the intermediacy of a 4' ketone, 1' aldehyde modified carbohydrate. An alternate mode of DNA degradation requires additional O2 and leads to formation of 3' phosphoglycolate termini and base propenals. Glycolate (GA), released from calf thymus DNA, poly(dA-dT) or d(CGCGCG) by enzymatic digestion, can be isolated by chromatography on DEAE Sephadex, silylated and analyzed by GC-MS. This analysis, after incubation with Fe(II) x 18O2 x BLM or Fe(III) x H216O2 x BLM plus 18O2, reveals the incorporation of a single atom of 18O at the C-1 position. Pulse-chase experiments demonstrate that it is the excess molecular oxygen and not the O2 required for drug activation that is incorporated into the carboxylate group of 3' phosphoglycolate and provide evidence for the proposed addition of O2 to a C4' carbon radical. Isotopic enrichments of the other products of DNA oxidation, formed in the presence of 18O2 are also being determined

  10. Clustering in non-self-conjugate nuclei 10Be and 18O

    Clustering phenomena in 10Be and 18O were studied by means of resonance elastic scattering of α-particles on 6He and 14C. Excitation functions for α+6He and α+14C were measured and detailed R-matrix analyses of the excitation functions was performed. We compare the experimental results with the predictions of modern theoretical approaches and discuss properties of cluster rotational bands

  11. Determination of the delta(18O/16O)of Water: RSIL Lab Code 489

    Revesz, Kinga; Coplen, Tyler

    2008-01-01

    The purpose of the technique described by the Reston Stable Isotope Laboratory (RSIL) lab code 489 is to present a method to determine the delta(180/160), abbreviated as delta-180, of water. This delta-18O measurement of water also is a component of National Water Quality Laboratory (NWQL in USGS) schedules 1142 and 1172. Water samples are loaded into glass sample containers on a vacuum manifold to equilibrate gaseous CO2 at constant temperature (25 deg C) with water samples. After loading water samples on the vacuum manifold, air is evacuated through capillary to avoid evaporation, and CO2 is added. The samples are shaken to increase the equilibration rate of water and CO2. When isotopic equilibrium has been attained, an aliquot of CO2 is extracted sequentially from each sample container, separated from water vapor by means of a dry ice trap, and introduced into a dual-inlet isotope-ratio mass spectrometer (DI-IRMS) for determination of the delta-18O value. There is oxygen isotopic fractionation between water and CO2, but it is constant at constant temperature. The DI-IRMS is a DuPont double-focusing mass spectrometer. It has a double collector. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other ion beams are collected in the front collector. The instrument is capable of measuring mass/charge (m/z) 44 and 45 or 44 and 46 by changing the ion-accelerating voltage under computer control. The ion beams from these m/z values are as follows: m/z 44=CO2=12C16O16O, m/z 45=CO2=13C16O16O primarily, and m/z 46 = CO2=12C16O18O primarily. The data acquisition and control software calculates delta-18O values.

  12. Interference effects between direct and sequential processes in the (18O, 16O reaction

    Cavallaro M.

    2014-03-01

    Full Text Available The 12C(18O, 16O14C reaction at 84 MeV has been studied at INFN-LNS laboratory using the MAGNEX magnetic spectrometer. High resolution energy spectra and cross-section angular distributions have been measured. DWBA calculations of both direct and sequential transfer to the 14C ground state show the important role of the interference between the two processes to describe the experimental data.

  13. Interference effects between direct and sequential processes in the (18O, 16O) reaction

    Cavallaro M.; Cappuzzello F.; Bondì M.; Carbone D.; Garcia V. N.; Gargano A.; Lenzi S.M.; Lubian J.; Agodi C.; Azaiez F.; De Napoli M.; Foti A.; Franchoo S.; Linares R.; Nicolosi D.

    2014-01-01

    The 12C(18O, 16O)14C reaction at 84 MeV has been studied at INFN-LNS laboratory using the MAGNEX magnetic spectrometer. High resolution energy spectra and cross-section angular distributions have been measured. DWBA calculations of both direct and sequential transfer to the 14C ground state show the important role of the interference between the two processes to describe the experimental data.

  14. Factors determining δ13C and δ18O fractionation in aragonitic otoliths of marine fish

    Thorrold, Simon R.; Campana, Steven E.; Jones, Cynthia M.; Swart, Peter K.

    1997-07-01

    Fish otoliths are aragonitic accretions located within the inner ear of teleost fish. The acellular nature of otoliths, along with taxon-specific shapes, chronological growth increments, and abundance in the fossil record suggest that the stable isotope chemistry of these structures may be unique recorders of environmental conditions experienced by fish in both modern and ancient water masses. To assess the factors determining δ 13C and δ 18O fractionation in fish otoliths, we reared Atlantic croaker ( Micropogonias undulatus) larvae under controlled environmental conditions. Metabolic effects apparently generated large isotopic disequilibria in the δ 13C values of M. undulatus otoliths. We found evidence of a negative regression between δ 13C- carbonate-δ 13C water (δ 13C) and temperature: δ 13C = -1.78 - 0.18 T °C However, this relationship was aliased to a degree by a positive correlation between δ 13C and somatic growth and otolith precipitation rates. Oxygen isotopes were deposited close to equilibrium with the ambient water. The relationship between temperature and the 18O/ 16O fractionation factor (α) was determined empirically to be: 1000 ln α = 18.56(10 3T K -1) - 32.54 The fractionation factor was not affected by either otolith precipitation or fish growth rates. Reconstruction of water temperature histories should, therefore, be possible from the δ 18O values of M. undulatus otoliths with a precision of 1°C, providing the δ 18O of the ambient water can be estimated.

  15. NanoSIMS50 analyses of Ar/18O2 plasma-treated Escherichia coli bacteria

    Reactive oxygen species (ROS) can be produced by electrical discharges and can be transported in uncharged regions by gas flows, in the so-called afterglows. These species are well known to have bactericidal effects but interaction mechanisms that occur with living micro-organisms remain misunderstood. In order to better understand these interactions, new analysis approaches are necessary. High-lateral-resolution secondary ion mass spectrometry (NanoSIMS) is one of the most promising ways of retrieving additional information on bacteria plasma inactivation mechanisms by combining isotopic imaging of plasma-treated bacteria and the use of 18O2 as process gas. Indeed, this technology combines a lateral resolution of a few tens of nanometres that is sufficient to image the interior of bacteria, and a high mass resolution allowing detection of isotopes present in low quantities (a few ppm or lower) within the bacteria. The present paper deals with Ar-18O2 (2%) plasma treatment, through low-pressure microwave late afterglows, of Escherichia coli bacteria and their elemental and isotopic imaging by NanoSIMS. E. coli bacteria have been exposed to this reactive medium for varying treatment duration while keeping all other parameters unchanged. Our main goal is to determine whether the quantity of 18O fixed in treated bacteria and the NanoSIMS50 lateral resolution are sufficient to give additional information on E. coli bacteria-plasma interaction. (paper)

  16. The 1996 thaw as a 18O tracer experiment at the lysimeter plant in Wagna

    In the year 1991 a research site was set up in Wagna in the western Leibnitz Field (Styria) which permits an examination of seepage water movement and of material transport as a function of the permeability of the uppermost soil layers and the underlying more coarsly clastic sediments under locale-specific natural management systems. Research at this site is largely based on hydrochemical and isotope-hydrological analysis. The 18O isotope is an ideal natural tracer of water movement. Infiltration water from the thaw following a snowy winter was displaced downward into the unsaturated zone as a result of a major precipitation event of 85.5 mm from April 2 to 5, 1996. This displacement is evident in the 18O concentrations of the seepage water at various measuring depths. The displacement is associated with recharge events, thaw processes tending to produce dispersive flows and precipitation events leading to ''piston flow effects. Winter precipitation water reaches a depth of 60 to 70 cm by mid-April. The attenuated 18O concentration reveals the predominant flow characteristics in the different compartments of the unsaturated zone (finely clastic soils, gravels, and sands)

  17. Finding of Neoproterozoic low-18O igneous rocks in the northern margin of the Dabie orogen

    ZHENG Yongfei; WU Yuanbao; ZHAO Zifu; GONG Bing

    2004-01-01

    @@ It has been one of the most intriguing questions in the earth sciences whether the snowball Earth event is genetically associated with mantle superwelling, supercontinent assemblage and breakup, and rift magmatism during the Neoproterozoic[1-4]. In order to demonstrate the occurrence of significant interaction in energy and matter between the earth's interior and exterior in this period, it is critical to find coeval igneous rocks that contain the signature of surface water and thus form low-18O magma.Several investigations of U-Pb dating and O isotope analysis were carried out for zircons from ultrahigh pressure (UHP) metamorphic rocks in the Dabie-Sulu orogen,east-central China[5-8]. The results indicate that low δ18O zircons have U-Pb ages of 700-800 Ma as dated by either TIMS discordia upper-intercept or SIMS in-situ magmatic core, and the origin of low δ18O water is related to cold paleoclimate during the Sturtian ice age.

  18. Delta(18)O characteristics of lichens and their effects on evaporative processes of the subjacent soil.

    Hartard, Britta; Máguas, C; Lakatos, M

    2008-03-01

    The study presents first data on the delta(18)O performance of poikilohydrous lichen ground cover, and its potential impact on the isotopic composition of water fluxes arising from subjacent soil layers. As a model organism, the globally distributed lichen Cladina arbuscula was studied under laboratory conditions as well as in the field. During a desiccation experiment, delta(18)O of the lichen's thallus water and of its respired CO(2) became enriched by approximately 7 per thousand and followed a similar enrichment pattern to that expected from homoiohydrous, vascular plants. However, the observed degree of enrichment was lower in comparison to vascular plants due to (i) the lichen's inherent lower evaporative resistances; and (ii) a stronger effect of the more depleted surrounding water vapour. In lichens growing in their natural habitat, this specific pattern may show substantial variations depending on prevailing microclimatic conditions. Within a field study, thallus water delta(18)O of lichens principally proved to become more depleted when close to equilibration with the surroundings. It thereby strongly depended on the absorption of surrounding water vapour. Moreover, the results indicate that lichen mats substantially reduce evaporation rates arising from subjacent soil layers, and may alter the isotopic signal of vapour diffusing away from these layers into more depleted values. PMID:18320432

  19. The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?

    Harris, Chris; le Roux, Petrus; Cochrane, Ryan; Martin, Laure; Duncan, Andrew R.; Marsh, Julian S.; le Roex, Anton P.; Class, Cornelia

    2015-07-01

    Oxygen isotope compositions of Karoo and Etendeka large igneous province (LIP) picrites and picrite basalts are presented to constrain the effects of crustal contamination versus mantle source variation. Olivine and orthopyroxene phenocrysts from lavas and dykes (Mg# 64-80) from the Tuli and Mwenezi (Nuanetsi) regions of the ca 180 Ma Karoo LIP have δ18O values that range from 6.0 to 6.7 ‰. They appear to have crystallized from magmas having δ18O values about 1-1.5 ‰ higher than expected in an entirely mantle-derived magma. Olivines from picrite and picrite basalt dykes from the ca 135 Ma Etendeka LIP of Namibia and Karoo-age picrite dykes from Dronning Maud Land, Antarctica, do not have such elevated δ18O values. A range of δ18O values from 4.9 to 6.0 ‰, and good correlations between δ18O value and Sr, Nd and Pb isotope ratios for the Etendeka picrites are consistent with previously proposed models of crustal contamination. Explanations for the high δ18O values in Tuli/Mwenezi picrites are limited to (1) alteration, (2) crustal contamination, and (3) derivation from mantle with an abnormally high δ18O. Previously, a variety of models that range from crustal contamination to derivation from the `enriched' mantle lithosphere have been suggested to explain high concentrations of incompatible elements such as K, and average ɛNd and ɛSr values of -8 and +16 in Mwenezi (Nuanetsi) picrites. However, the primitive character of the magmas (Mg# 73), combined with the lack of correlation between δ18O values and radiogenic isotopic compositions, MgO content, or Mg# is inconsistent with crustal contamination. Thus, an 18O-enriched mantle source having high incompatible trace element concentration and enriched radiogenic isotope composition is indicated. High δ18O values are accompanied by negative Nb and Ta anomalies, consistent with the involvement of the mantle lithosphere, whereas the high δ18O themselves are consistent with an eclogitic source. Magma δ18

  20. The use of 3H and 18O tracers to characterize water inflows in Alpine tunnels

    Water inflows in 9 tunnels and galleries through the Alpine crystalline massifs have been analysed for their 3H activities and δ18O contents. Tritium provides information on water transit times and the dynamics of deep water circulation, whereas δ18O contributes to understanding the origin and flow paths of water in such mountainous regions. Owing to ambiguities arising from the irregularity of the historical 3H input function since 1945, a unequivocal and straightforward interpretation of water transit times in Alpine tunnels is not possible. Nevertheless, the ambiguity can be resolved by considering the 3H data in combination with (a) the generalized hydraulic conductivity of the massif obtained from discharge data, and (b) the Na and silica content of the water as an indication of the extent of rock-water interaction. When the data are resolved in this way, the waters that were sampled in the tunnels/galleries can be divided into 3 age groups, i.e. 40 a. In general, water beneath a rock-cover thickness of 3H content of a water inflow in the Gothard gallery. Oxygen-18 data primarily reflect the recharge altitude, which can be predicted a priori by considering the large-scale geological structures of each massif and the extent to which they control the subvertical paths followed by the groundwater. Anomalous δ18O data may reflect local or general departures from this interpretation. A general pattern is that downslope flow in the better jointed 'decompressed zone', which parallels the topography, may divert recharge from a higher to lower altitude before it follows the structural pathways into the tunnel. This results in a somewhat lower δ18O value than would be predicted from structure alone, but tends to confirm the existence and role of the 'decompressed zone' indicated by the 3H. More local δ18O anomalies reflect recharge from rivers or lakes entering the tunnels, and are illustrated by examples in this paper. Results show that environmental isotopes

  1. ({sup 18}O,{sup 16}O) Two-neutron transfer reactions for spectroscopic studies

    Cavallaro, Manuela; Agodi, Clementina; Bondi, Mariangela; Cappuzzello, Francesco; Carbone, Diana; Cunsolo, Angelo; Foti, Antonino; Napoli, Marzio de; Nicolosi, Dario; Tropea, Stefania [University of Catania, INFN-LNS and INFN-Sez., Catania (Italy); Lubian, Jesus; Garcia, Vantelfo; Paes, Barbara [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Fisica

    2012-07-01

    Full text: The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C and {sup 13}C({sup 18}O,{sup 17}O){sup 14}C transfer reactions have been studied at 84 MeV incident energy at the INFN-LNS laboratory in Catania (Italy). The {sup 16}O and {sup 17}O ejectiles were detected at forward angles by the MAGNEX large acceptance magnetic spectrometer. Q-value spectra up to about 20 MeV and angular distributions were obtained with resolution of about 150 keV in energy and 0.2 deg in angle. In particular, excited states with relevant 1p-3h configuration with respect to the {sup 16}O core are mainly populated by the ({sup 18}O,{sup 17}O) reaction while states with known 2p-4h configuration are excited by the ({sup 18}O,{sup 16}O). This demonstrates the clear selectivity of such reactions. The shape of the measured angular distributions is found to be sensibly dependent on the transferred angular momentum. A theoretical description based on exact finite range coupled reaction channel calculations using the double folding Sao Paulo potential is used for the first time to analyze the data. The good agreement with the experimental cross section demonstrates that, despite the heavy ions involved, the one-step transfer of a two-neutron pair is dominant in the ({sup 18}O,{sup 16}O) reaction. A comparison with Distorted Wave Born Approximation calculations using the same potential shows that effects of channel couplings is visible but small. Supplementary two-neutron sequential transfer calculation are performed within the two-step DWBA formalism, introducing the intermediate partition {sup 13}C + {sup 17}O. This accounts only for a negligible contribution to the absolute cross section. As a consequence, the possibility to extract two-particle spectroscopic factor and, more in general, information on nuclear structure is demonstrated. (author)

  2. An investigation of the controls on Irish precipitation {delta}{sup 18}O values on monthly and event timescales

    Baldini, Lisa M.; Baldini, James U.L. [Durham University, Department of Earth Sciences, Durham (United Kingdom); McDermott, Frank; Moellhoff, Martin [University College Dublin, UCD School of Geological Sciences, Dublin 4 (Ireland); Fischer, Matthew J. [Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Menai, NSW (Australia)

    2010-11-15

    This two-year study investigates the relative influence of meteorological variables (precipitation amount and temperature), atmospheric circulation, air mass history, and moisture source region on Irish precipitation oxygen isotopes ({delta}{sup 18}O{sub p}) on event and monthly timescales. Single predictor correlations reveal that on the event scale, 20% of {delta}{sup 18}O{sub p} variability is attributable to the amount effect and 7% to the temperature effect while on the monthly timescale the North Atlantic Oscillation accounts for up to 20% of {delta}{sup 18}O{sub p} variability and the amount and temperature effects are not significant. In comparison, multivariate linear regression reveals that the interaction of temperature and precipitation amount explains up to 40% of {delta}{sup 18}O{sub p} variance at event and monthly timescales. Five-day kinematic back trajectories suggest that the amount-weighted mean {delta}{sup 18}O{sub p} value of southerly- and northerly-derived events are lower by 2 permille relative to events derived from the west. Because air mass history and atmospheric circulation appear to influence {delta}{sup 18}O{sub p} in Ireland, Irish paleo-{delta}{sup 18}O{sub p} proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall. (orig.)

  3. The use of micro-Raman imaging to measure 18O tracer distribution in thermally grown zirconia scales

    Highlights: • High temperature oxidation of Zircaloy-4 was studied by coupling 18O diffusion and Raman imaging. • Shifts of the monoclinic ZrO2 Raman lines versus the 18O content were calibrated. • 18O diffusion profiles were obtained through micro-Raman scanning. • Protective influence of a pre-transient corrosion scale has been investigated. - Abstract: High temperature Zircaloy-4 oxidation has been studied through two-stage oxidation experiments using 18O isotope. 18O distribution in the oxidation scales was investigated by micro-Raman imaging. First, zirconia standards with known 18O content were prepared and analyzed for calibration purposes. Then, to assess the method on a simple case, 18O tracer penetration patterns were recorded after a 800 °C two-stage oxidation. Finally, oxidation at 850 °C of a Zircaloy4 cladding tube pre-corroded at 425 °C to simulate corrosion during normal reactor operation was studied. These preliminary results give insights on the protective nature of the first formed zirconia scale in case of an accident

  4. Relationships between δ18O in summer precipitation and temperature and moisture trajectories at Muztagata, western China

    2006-01-01

    Based on summer observations of stable isotope of precipitation at Muztagata, western China, during 2002―2003, this paper presents the relationship between δ18O in precipitation and air temperature, and discusses the effect of moisture transport on δ18O in precipitation. Results show that air temperature correlates positively with δ18O in precipitation, and the temperature effect controls the δ18O of precipitation in this area. The Muztagata region exhibits high δ18O values in summer precipitation, similar to those shown at stations in adjacent regions. According to the results of our model set up to trace the moisture trajectories, the westerlies and local moisture circulation contribute to variations of oxygen isotopes in precipitation. In addition, the impacts of the moisture transport distance, the moisture transport level, and the incursion of the polar air mass also influence the variations of δ18O in precipitation. The moisture origins and transport mechanisms also contribute to the variation of δ18O in precipitation at Muztagata.

  5. Past break-monsoon conditions detectable by high resolution intra-annual δ18O analysis of teak rings

    Managave, S. R.; Sheshshayee, M. S.; Borgaonkar, H. P.; Ramesh, R.

    2010-03-01

    Intra-annual variations in the cellulose oxygen isotopic composition (δ18O) of several annual growth rings of three teak (Tectona grandis L.F.) trees from central India show a clear seasonal cycle with higher values in the early and late growing seasons and lower values in the middle. This cycle is useful to identify growth occurring during different phases of the growing season. Relative humidity (RH) appears to control the intra-annual δ18O variations rather than rainfall, and therefore past break-monsoon conditions associated with lower RH, could be detected by high resolution sub-sampling of annual rings for δ18O analysis.

  6. In Situ Raman Spectroscopy of Supported Transition Metal Oxide Catalysts: 18O2-16O2 Isotopic Labeling Studies

    Weckhuysen, B.M.; Jehng, J.M.; Wachs, I.E.

    2000-01-01

    The isothermal isotopic exchange reaction of 18O2 with 16O of CrO3, MoO3, Nb2O5, WO3, V2O5, and Re2O7 supported on ZrO2 has been investigated with in situ laser Raman spectroscopy. Isotopic exchange of the oxygen atoms of the supported transition metal oxides with 18O2 is difficult and requires several successive reduction-18O2 reoxidation cycles at relatively high temperatures. The Raman spectroscopy data reveal that all the supported transition metal oxides are present as a monooxo species ...

  7. Nuclear and astrophysical aspects of 18O(p,γ)19F

    The capture reaction 18O(p,γ)19F has been investigated in the energy range Esub(p) = 80-2200 keV. The seven known resonances have been studied in detail and twelve new resonances have been found. The resonances at Esub(R) = 680, 977 and 1670 keV correspond to new states in 19F. The known resonance at Esub(R) = 631 keV is observed to consist of a doublet (ΔEsub(p) = 7 keV). Information on resonance energies, total and partial widths, branching and mixing ratios and ωγ values is reported. Transition strength arguments as well as analyses of γ-ray angular distribution data combined with results from previous work resulted in Jsup(π) assignments for some of the resonances and low-lying states in 19F. The assignment of several states in 19F as T = 3/2 analogue states of 19O is discussed. A direct capture process to several final states in 19F up to Esub(x) = 8.8 MeV has been observed revealing information on the orbital momenta of the captured protons in the final states, their spectroscopic factors and Jsup(π) assignments for interfering resonances. Special efforts were made to detect this process to states near the proton threshold, which are of importance to stellar hydrogen burning of 18O. The results are compared with corresponding information from other reactions. The investigated energy range of the 18O(p,γ)19F reaction corresponds to the important stellar temperature range of T = 0.01 to 5 X 109 K. The energy-averaged astrophysical reaction rates determined from the present data are compared with previous estimates for this reaction. The data permit reliable conclusions to be drawn concerning the final termination of the CNO tri-cycle. (orig.)

  8. delta 18O variations in snow on the Devon Island ice cap, Northwest Territories, Canada

    A study of delta18O variations of snow samples taken on traverses across the Devon Island ice cap in June 1971, 1972, and 1973 has shown a difference between the accumulation conditions on the souteast and nortwest sides of the ice cap. On the souteast side there is an increasing depletion of 18O in the snow with increasing elevation. This pattern is attibuted to the effect of orographic uplift of air masses moving over the ice cap from the southeast, which promotes condensation and precipitation due to adiabatic cooling. On the northwest side of the ice cap there is no evidence of any further depletion of 18O in snow, neither with increasing distance from the possible moisture source in Baffin Bay to the southeast nor with increasing elevation if the air mass comes from the northwest. In this case condensation is due to isobaric cooling so that precipitation is generally from level cloud bases. The changes inferred for the isotopic composition of the water vapour as it rises up the southeast slope are found to be consistent with its depletion through precipitation under near-equilibrium conditions. It is calculated that approximately 30% of the moisture at sea level on the southeast side of the ice cap and 8% at the top of the ice cap are of local origin. Lower temporal and aerial variability of the delta values on the southeast side of the ice cap is attributed to dominance of the Baffin Bay low on that side Effecting consistency of storm conditions there. The delta values of ice in the ablation zone on the Sverdrup Glacier show the combined effect of ice movement from the accumulation to the ablation zone and climatic change during the period of movement from cold to warm and back to cold conditions again. (auth)

  9. Thermal neutron capture cross sections for 16,171,18O and 2H

    Firestone, R. B.; Revay, Zs.

    2016-04-01

    Thermal neutron capture γ -ray spectra for 16,17,18O and 2H have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and O,1817 enriched D2O targets. Complete neutron capture γ -ray decay schemes for the 16,17,18O(n ,γ ) reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the γ -ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV γ ray from 16O(n ,γ ) was measured as Pγ(871 )=96.6 ±0.5 % and the thermal neutron cross section for this γ ray was determined as 0.164 ±0.003 mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose γ -ray cross sections were previously standardized. The γ -ray cross sections for the O,1817(n ,γ ) and 2H(n ,γ ) reactions were then determined relative to the 870.76-keV γ -ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the γ -ray cross sections and transition probabilities; σ0(16O )=0.170 ±0.003 mb; σ0(17O )=0.67 ±0.07 mb; σ0(18O )=0.141 ±0.006 mb; and σ0(2H )=0.489 ±0.006 mb.

  10. {sup 18}O/{sup 16}O determination in organic matter

    Saurer, M.; Siegwolf, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The oxygen isotope ratio in plant material can be used to deduce information about the climate and the environment. We present a simple and fast continuous-flow technique for the determination of the {sup 18}O/{sup 16}O ratio in organic matter. In this method the samples are thermally decomposed in the presence of glassy carbon and the evolving monoxide is used to determine the oxygen ratio. Not only cellulose but also nitrogen-containing materials can be processed when interfering gases (mainly N{sub 2}) are separated from CO by gas chromatography. (author) 2 figs., 2 refs.

  11. A culture-based calibration of benthic foraminiferal paleotemperature proxies: δ18O and Mg/Ca results

    D. C. McCorkle

    2010-01-01

    Full Text Available Benthic foraminifera were cultured for five months at four temperatures (4, 7, 14 and 21 °C to establish the temperature dependence of foraminiferal δ18O and Mg/Ca. Two Bulimina species (B. aculeata and B. marginata were most successful, adding chambers at all four temperatures and reproducing at 7 and 14 °C. Foraminiferal δ18O values displayed ontogenetic variations, with lower values in younger individuals. The δ18O values of adult specimens decreased with increasing temperature in all but the 4 °C treatment, exhibiting a relationship consistent with previous δ18O paleotemperature calibration studies. Foraminiferal Mg/Ca values, determined by laser ablation inductively coupled plasma mass spectrometry, were broadly consistent with previous Mg/Ca calibration studies, but extremely high values in the 4 °C treatment and higher than expected values at two of the other three temperatures make it challenging to interpret these results.

  12. Temperature variations in the past 6000 years inferred from δ18O of peat cellulose from Hongyuan, China

    2002-01-01

    Trends of the temperature variations recorded in δ18O in Hongyuan peat cellulose are similar to those recorded in δ 18O of Jinchuan peat cellulose and inδ18O of Dunde ice core. Climate events have been identified to be globallyhomogeneous. Two notable climate transition periods have been detected in the past 6000 years, namely 4000 aBP with climate shifting from cold to warm and 1500aBP with climate shifting from warm to relatively cold. Power spectrum analysiswas performed to investigate the periodical signals in the δ18O time series. Typical periodicities of 1200-1087 a, 752 a, 444 a, 325 a, 213 a, 127-123 a, 88a, 79 a were discovered, indicating an integrated influence on Hongyuan climatefrom solar, monsoon and ocean activities. Solar forcing has been addressed to be the main driving forcing of Hongyuan climate.

  13. Validation of δ18O as a proxy for past monsoon rain by multi-GCM simulations

    Midhun, M.; Ramesh, R.

    2016-03-01

    Stable oxygen isotope ratios (δ18O) of tree cellulose and speleothem carbonate are useful proxies for past monsoon rain in many tropical regions, as a decrease in rain δ18O is observed with increase in rainfall on a monthly time scale. This amount effect varies spatially; therefore a local calibration, with actual measurements of rain amount and its δ18O is required. Such observations, however, are quite limited in space and time. To circumvent this difficulty, many isotope enabled general circulation models (GCMs) are used to aid the interpretation of 18O proxies; nevertheless, all such simulations taken together are yet to be evaluated against observations over the Indian summer monsoon (ISM) region. Here we examine ten such GCM simulations archived by the stable water isotope INtercomparison Group, phase 2. The spatial patterns of simulated ISM rainfall and its δ18O are in good agreement with the limited observations available. Simulations nudged with observed wind fields show better skill in reproducing the observed spatio-temporal pattern of rainfall and its δ18O. A large discrepancy is observed in the magnitude of the simulated amount effect over the Indian subcontinent between the models and observation, probably because models simulate the spatial distribution of monsoon precipitation differently. Nudged simulations show that interannual variability of rainfall δ18O at proxy sites are controlled by either regional (rather than local) rainfall or upstream rain out. Interannual variability of rainfall δ18O over the East Asian region is well correlated with ENSO, while it is only weakly correlated over the Indian sub-continent.

  14. Establishing a grassland signature in veins: 18O in the leaf water of C3 and C4 grasses

    Helliker, Brent R.; Ehleringer, James R.

    2000-01-01

    We show that 18O evaporative enrichment of bulk leaf water in grass species can be significantly more enriched than predicted by the Craig–Gordon model, with C4 grasses considerably more enriched than C3 grasses. Our results suggest that the unanticipated 18O leaf water enrichment of grasses is attributable to the progressive evaporative enrichment along parallel veins (a function of both leaf length and interveinal distance), a pattern that does not occur in Dicotyledonous species. We propos...

  15. Intramolecular (18O) isotopic exchange in the gas phase observed during the tandem mass spectrometric analysis of peptides

    Fast atom bombardment/tandem mass spectrometry of protonated and metal cationized peptides has revealed evidence for novel intramolecular rearrangements in the gas phase. Second generation product ion scanning (MS/MS/MS) analyses of the protonated (18O2) analogues established that both isotope labels are located at the new C-terminus formed via the rearrangement. The kinetic energies released during the formation of the (18O1)-and (18O2)-labeled rearrangement products are indistinguishable, consistent with the involvement of a common intermediate. First generation product ion spectra (MS/MS) of protonated (18O2)-peptides include fragments arising from simple peptide bond cleavage which show isotope enrichments consistent with immediate precursor ions which incorporate (18O) at the peptide bond between the penultimate and C-terminal amino acid residues. Several lines of evidence eliminate the possibility of such incorporation of label during solution-phase preparation of the (18O2)-labeled analogues. Thus, the combined data are in accord with an isotope exchange process occurring in the gas phase, most likely through a mechanism involving the reversible formation of a cyclic intermediate. These studies, combined with previous data, emphasize the importance of the conformations adopted by gas-phase peptide ions in influencing fragmentation pathways. 30 refs., 8 figs

  16. An isotope mass balance model for the correlation of freshwater bivalve shell (Unio pictorum carbonate δ18O to climatic conditions and water δ18O in Lake Balaton (Hungary

    Gabriella SCHÖLL-BARNA

    2011-08-01

    Full Text Available The oxygen isotope composition of bivalve shells (δ18Oshell can potentially record environmental variability of shallow lakes and therefore it has been extensively used as a proxy in the reconstruction of past climate and environmental conditions. As δ18Oshell reflects - besides the water temperature - the oxygen isotope composition of lake water (δ18OL, it is required to interpret the quality and impact of parameters influencing the δ18OL. Using the isotope mass balance model, I tested the hypothesis that Balaton lake water δ18O variability can be described as a result of the combined effects of three main climatic parameters such as river runoff, precipitation and evaporation. I calculated δ18OL time series for the period 1999-2008 for the whole water body at Siófok (eastern part of Lake Balaton, Hungary based on measured precipitation, inflow and evaporation amount and measured inflow, precipitation δ18O and calculated vapour δ18O data. The comparison of the modelled δ18OL time series to measured surface δ18OL data revealed that δ18O of Balaton water is sensitive for variation of climatic parameters. This variability is most striking at the surface, while according to the results of the model, the whole water body itself is less sensitive. Monthly differences suggest that generally during summer the whole water body is mixed up, while moderate isotope stratification (0.3-0.7‰ difference between surface and whole water body can be assumed in early spring and autumn. Predictions of shell δ18O values were made using the measured surface water δ18O data and the modelled δ18O values for the whole water body. High-resolution sampling was conducted on two Unio pictorum shells covering the period of 2001-2008, and both predictions were compared to measured shell δ18O records. The results showed that the prediction for the whole water body gives a better fit to the measured shell δ18O, suggesting that the whole water body better

  17. 18O/16O ratio in groundwater of the Federal Republic of Germany

    More than 900 groundwater samples of 480 municipal water factories were collected at the area of the Federal Republic of Germany. The 18O/16O-ratio decreases from the north (-7per mill) to south (below -11per mill) due to an increasing distance from the south ('continental effect') and an increasing altitude above sealevel ('altitude effect'). The decrease of the 18O/16O-ratio per 1000 m altitude above sea level is 2.8per mill, per 1000 km distance from the sea 2.4per mill. At the coast an initial value of -7.2per mill results from the multicorrelation analysis. Except of two cases, some samples near to the coast and alongside river Rhine, the groundwater samples represent the mean oxygen isotope ratio of the local precipitation. This oxygen isotope ratio will be found in the conductive tissues of the plants (trees), too. Therefore the knowledge of the natural variation of the oxygen isotope ratio can serve as a tool in studies of plant physiology, water ecology, palaeclimatology and food analysis. (orig.)

  18. Inferring heterogeneity in aquitards using high-resolution deltaD and delta18O profiles.

    Hendry, M Jim; Wassenaar, L I

    2009-01-01

    Vertical depth profiles of pore water isotopes (deltaD and delta18O) in clay-rich aquitards have been used to show that solute transport is dominated by molecular diffusion, to define the timing of geologic events, and to estimate vertical hydraulic conductivity. The interpretation of the isotopic profiles in these studies was based on pore water samples collected from piezometers installed in nests (typically 4 to 15 piezometers) over depths of 10 to 80 m. Data from piezometer nests generally have poor vertical resolution (meters), raising questions about their capacity to reveal the impact of finer scale heterogeneities such as permeable sand bodies or fractured till zones on solute transport. Here, we used high-resolution (30-cm) depth profiles of deltaD and delta18O from two continuously cored boreholes in a till aquitard to provide new insights into the effects of sand bodies on solute transport. High-resolution core-derived profiles indicate that such heterogeneities can cause major deviations from one-dimensional diffusion profiles. Further, comparison of piezometer-measured values with best-fit diffusion trends shows subtle deviations, suggesting the presence of heterogeneities that should not be ignored. High-resolution profiles also more clearly defined the contact between the highly fractured oxidized zone and the underlying unoxidized zone than the piezometers. PMID:19735307

  19. ENSO flavors in a tree-ring δ18O record from Indonesia

    Schollaen, Karina; Karamperidou, Christina; Helle, Gerhard

    2014-05-01

    The existence of so-called ENSO flavors (Cold Tongue and Warm Pool El Nino), their underlying mechanisms and potential changes in their frequency of occurrence is an active field of research in the climate science community. Previous work has shown the distinct teleconnection patterns of ENSO flavors and SST, precipitation and salinity in the tropics, which should be taken into account when interpreting palaeo-climate proxies. At the same time, proxies from key locations with distinct ENSO-flavors signals can provide long continuous records, essential for identifying possible trends and (multi)decadal variability of ENSO flavor occurrence. Here, we show that one such key region is Java (Indonesia), where the ENSO influence on precipitation is significant for Warm Pool ENSO, and non-significant for Cold Tongue ENSO. We do so by investigating the ENSO signal in a 108-year long (1900-2007) tree-ring δ18O record of teak (Tectona grandis) trees growing in a lowland rain forest in Central Java. Climate response analysis with regional monthly rainfall data reveals that the tree-ring δ18O record is significantly correlated to rainfall, and is sensitive to the occurrence of Warm Pool ENSO events, as well as La Nina events. The results presented here demonstrate the ability of tree-ring stable isotope records to provide palaeo-climate records able to distinguish between the two ENSO flavors, with broad applicability to studies on past ENSO variability.

  20. A high-resolution δ18O record and Mediterranean climate variability

    C. Taricco

    2014-10-01

    Full Text Available A~high-resolution, well-dated foraminiferal δ18O record from a shallow-water core drilled from the Gallipoli Terrace in the Gulf of Taranto (Ionian Sea, previously measured over the last two millennia, has been extended to cover 707 BC–1979 AD. Spectral analysis of this series, performed by Singular Spectrum Analysis (SSA and other classical and advanced methods, strengthens the results obtained analysing the shorter δ18O profile, detecting the same highly significant oscillations of about 600 yr, 380 yr, 170 yr, 130 yr, and 11 yr, respectively explaining about 12%, 7%, 5%, 2% and 2% of the time series total variance, plus a millennial trend (18% of the variance. The comparison with the results of Multi-channel Singular Spectrum Analysis (MSSA applied to a data set of 26 Northern Hemisphere (NH temperature-proxy records shows that NH temperature anomalies share with our local record a long-term trend and a bicentennial cycle. These two variability modes, previously identified as temperature-driven, are the most powerful modes in the NH temperature data set. Both the long-term trends and the bicentennial oscillations, when reconstructed locally and hemispherically, show coherent phases. Also the corresponding local and hemispheric amplitudes are comparable, if changes in the precipitation-evaporation balance of the Ionian sea, presumably associated with temperature changes, are taken into account.

  1. Runoff modeling of the Amazon basin using 18 O as a conservative tracer

    Using the δO18 O content of natural waters as a conservative tracer, a runoff modelling of the Amazon river basin was carried out in order to study the hydrological characteristics of the precipitation-runoff relationship. Measurements of the δ18 O in rainfall waters made in the high Solimoes region at Benjamin Constant, in the central part of basin at Manaus, and at the mouth near the Marajo Island, while the river waters were measured at Obidos only, as a proxy for the mouth, during the 1973-1974 hydrological years. The hydrography separation of the Amazon river was performed using the isotopic method to estimate the contributions of the surface runoff (event water) and baseflow (pre-event water) components to the total river flow. At peak discharge, the average contribution of the baseflow was 57% of the total river flow. The annual average contributions for surface runoff and baseflow were 30.3 and 69.7%, respectively. The residence time of the subsurface water in the basin was estimated as being 7 months, by fitting a sinusoidal function to the isotopic values of rainfall and river waters. The low values of the amplitude damping in the basin suggest high mixing waters during the runoff process. (author). 21 refs., 4 figs., 1 tab

  2. Millennial-scale features in ?18O from a stalagmite in the eastern United States

    Hardt, B. F.; Doctor, D. H.; Gao, Y.; Rowe, H. D.; Cheng, H.; Edwards, R.

    2013-12-01

    The oxygen isotope record of calcite from a stalagmite collected from Grand Caverns in Virginia, USA shows evidence of millennial-scale variability that appears to be coherent with Dansgaard/Oeschger events observed in Greenland ice. Sample GC-S02 grew from 82 - 13 ka BP and ranges in δ18O composition from -8 to -4 ‰ (VPDB) with multiple instances of millennial-scale changes in excess of 1‰. As δ18O in GC-S02 is more positive during MIS 2 than MIS 3, change in mean annual temperature is not a likely explanation for the observed variability. The carbon and oxygen isotopic records of calcite are independent and show no evidence of covaration (r = -0.1). Changes in the seasonal timing of precipitation provides an alternate explanation for the data, particularly given the potential for warm- and cool-season precipitation to come from different sources (Gulf of Mexico versus the Atlantic ocean). Grand Caverns is located in the Shenandoah River watershed within the Appalachian Great Valley, suggesting a meaningful role for Atlantic moisture. The age model is based on high-precision U-Th ages, making this record a potential benchmark for the region.

  3. Validating methods for measuring delta18O and delta13C in otoliths from freshwater fish.

    Guiguer, K R R A; Drimmie, R; Power, M

    2003-01-01

    The ability of the phosphoric acid digestion technique to extract carbon dioxide from biogenic carbonates and reliably reproduce delta(18)O and delta(13)C signatures from standard reference materials (NBS-18, NBS-19) was tested and shown to produce accurate, unbiased measurements of non-biologic materials. The effects of roasting preparation methods commonly reported when analyzing biogenic carbonates were also tested in a series of experiments using reference standards and otoliths obtained from aquacultured Arctic charr and rainbow trout. Roasting had no effect on the isotope measurement of reference standards. No significant differences between mean oxygen isotope signatures from paired experiments with roasted and non-roasted fish otoliths were found. However, otolith oxygen isotope measurements were significantly enriched in comparison to rearing water-based measurements for both species. Agreement between expected isotopic equilibrium and measured otolith delta(18)O values varied as a function of roasting temperature and between species. Criteria for the selection of appropriate roasting temperatures are suggested and favour 350 degrees C in freshwater fish where unbiased estimates of average rearing water temperatures and known differences in rearing temperatures were obtained. Carbon isotopic disequilibria were observed for both species. A mixing model analysis established differences in the percentage of metabolically derived carbon in studied otoliths, with Arctic charr deriving a greater proportion of otolith delta(13)C from metabolism as a result of higher metabolic rates. PMID:12590395

  4. Relative discharge of the Amazon River and its main tributaries as measured using 18O values

    Discharge measurement of large rivers such as the Amazon and its tributaries is far from easy. On the other hand, the river discharge is an essential parameter for assessing the chemical and sediment load of a river. Under certain conditions the water oxygen isotope composition is a useful tool for estimating the relative contribution of a tributary to the main channel of a basin. In addition, if the final discharge is known, it will be possible to quantify the tributary discharge and the main channel discharge before their confluence. The required condition for the use of this technique is that the difference between the δ18O values of the main channel and those of its tributaries is large enough to allow measurement by mass spectrometry. This condition was found in five reaches of the Amazon River. The relative contributions of the tributaries Ica, Jutai, Purus, Negro and Madeira were estimated during different stages of the Amazon hydrograph. Finally, the results were compared with the discharge value measured by Richey et al. at the same time as sampling water for the determination of isotope composition. In general, the relative discharges estimated by using the δ18O values were in accordance with the values measured by a depth-integrated sampler

  5. Isolating relative humidity: dual isotopes d18O and dD as deuterium deviations from the global meteoric water line

    Cellulose d18O and dD can provide insights on climates and hydrological cycling in the distant past and how these factors differ spatially. However, most studies of plant cellulose have used only one isotope, most commonly d18O, resulting in difficulties partitioning variation in d18O of precipitati...

  6. First results from a novel methodological approach for δ18O analyses of sugars using GC-Py-IRMS

    Zech, Michael; Saurer, Matthias; Tuthorn, Mario; Rinne, Katja; Werner, Roland; Juchelka, Dieter; Siegwolf, Rolf; Glaser, Bruno

    2013-04-01

    Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ18O analyses is commercially available for more than 10 years, this method is hardly applied by isotope researchers so far. Using GC-Py-IRMS, Zech and Glaser (2009) and Zech et al. (2013; 2012) developed and applied a method, which allows determining δ18O of hemicellulose-derived sugar biomarkers extracted from soils and sediments. However, the used methylboronic acid (MBA) derivatization is suitable only for pentoses and deoxyhexoses, not for hexoses. Here we present first GC-Py-IRMS results for TMS-(trimethylsilyl)-derivatives of plant sap-relevant sugars (glucose, fucose, sucrose, raffinose) and a polyalkohol (pinitol) produced using BSTFA (N,O-Bis(trimethylsilyl)trifluoroacetamide) as the derivatization reagent. Particularly, we focus on sucrose, which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and in tree-ring studies. Replicate analyses of sucrose standards with known δ18O values suggest that the δ18O measurements are not stable over several days. A calibration (including a drift correction) against an external sucrose standard is hence essential when measuring sample batches. Furthermore, we observed a large dependence of the δ18O values on the analyte amount (area), which needs to be considered by a respective correction procedure. Tests with 18O-enriched water do not provide any evidence for oxygen exchange reactions between water and sucrose, glucose and raffinose. Finally we present the first application of compound-specific δ18O analyses from natural samples, namely from seven needle extracts (soluble carbohydrates) from a Siberian study area. Both the δ18O amplitude and values of sucrose are considerably higher (32.1‰ to 40.1‰) compared to the δ18O amplitude and values of bulk needle extract (24.6‰ to 27.2‰). We found positive correlation (although

  7. /sup 12/C(/sup 16/O,. cap alpha. )/sup 24/Mg( reaction in the energy region E/sub c. m. / = 26. 6 to 42. 9 MeV

    Bechara, M.J.; Lazzarini, A.J.; Ledoux, R.J.; Cosman, A.E.R.

    1983-04-01

    The /sup 12/C+ /sup 16/O resonance structure in the /sup 28/Si nucleus is examined by means of the /sup 12/C(/sup 16/O,..cap alpha..)/sup 2r/Mg reaction excitation functions in the energy range E/sub c.m./ = 26.6 to 42.9 MeV in 430 keV steps at theta/sub lab/ = 7.5/sup 0/. We could identify 64 discrete states in /sup 24/Mg up to 31.7 MeV of excitation energy. The excitation functions show abundant structure over the entire energy range. The summed excitation functions, which tend to average out statistical fluctuations, show pronounced intermediate structure enhancement in the cross section at E/sub c.m./approx. =29.5, 32.2, and 35 MeV and indicate the presence of a smaller peak at 37.3 MeV. The widths of these structures are about 1 MeV, which is intermediate between the value expected from ion-ion potential resonances and statistical fluctuations. The nonstatistical character of these structures is reinforced by some statistical tests and by the correlations in energy and width found in several exit channels. Our data also suggest a possible structural relationship between the /sup 28/Si resonances and certain /sup 24/Mg final states.

  8. Tracking Cats: Problems with Placing Feline Carnivores on δ18O, δD Isoscapes

    Pietsch, Stephanie J.; Hobson, Keith A.; Wassenaar, Leonard I.; Tütken, Thomas

    2011-01-01

    Background Several felids are endangered and threatened by the illegal wildlife trade. Establishing geographic origin of tissues of endangered species is thus crucial for wildlife crime investigations and effective conservation strategies. As shown in other species, stable isotope analysis of hydrogen and oxygen in hair (δDh, δ18Oh) can be used as a tool for provenance determination. However, reliably predicting the spatial distribution of δDh and δ18Oh requires confirmation from animal tissues of known origin and a detailed understanding of the isotopic routing of dietary nutrients into felid hair. Methodology/Findings We used coupled δDh and δ18Oh measurements from the North American bobcat (Lynx rufus) and puma (Puma concolor) with precipitation-based assignment isoscapes to test the feasibility of isotopic geo-location of felidae. Hairs of felid and rabbit museum specimens from 75 sites across the United States and Canada were analyzed. Bobcat and puma lacked a significant correlation between H/O isotopes in hair and local waters, and also exhibited an isotopic decoupling of δ18Oh and δDh. Conversely, strong δD and δ18O coupling was found for key prey, eastern cottontail rabbit (Sylvilagus floridanus; hair) and white-tailed deer (Odocoileus virginianus; collagen, bone phosphate). Conclusions/Significance Puma and bobcat hairs do not adhere to expected pattern of H and O isotopic variation predicted by precipitation isoscapes for North America. Thus, using bulk hair, felids cannot be placed on δ18O and δD isoscapes for use in forensic investigations. The effective application of isotopes to trace the provenance of feline carnivores is likely compromised by major controls of their diet, physiology and metabolism on hair δ18O and δD related to body water budgets. Controlled feeding experiments, combined with single amino acid isotope analysis of diets and hair, are needed to reveal mechanisms and physiological traits explaining why felid hair does

  9. Hydrochemistry and 18O/16O and 2H/1H Ratios of Ugandan Waters

    Gebremichael, M. G.; Jasechko, S.

    2013-12-01

    Today, 70% of the 35 million people living in Uganda have access to an improved water source, ranking Uganda 148 out of 179 nations reporting in 2010 (Millennium Development Goals Indicators). 80% of Ugandans rely on groundwater as their primary drinking water source, collecting at springs or from shallow wells. Similarly, 80% of Ugandans rely upon agriculture - usually rain fed - as their primary income source. Despite lack of access to protected water sources faced by 10 million Ugandans, and the importance of the blue economy to Uganda's continued development, a country-wide investigation of the chemistry and the stable oxygen and hydrogen isotope compositions of waters has yet to be completed. Here we present 250 analyses of 18O/16O, 2H/1H and dissolved ion concentrations of Ugandan lakes, rivers, groundwaters and springs collected during July, 2013. We use the new data to characterize regional scale groundwater recharge sources, advection pathways and interactions with surface waters. Large lakes - Albert, Edward and Victoria - show increases in 18O/16O and 2H/1H ratios consistent with open water evaporation, and are shown to be distinct from nearby groundwaters, suggesting minimal recharge from large lakes to the subsurface. Salinities of eastern Ugandan groundwaters are elevated relative to samples collected from the central and western regions, suggesting that longer groundwater residence times and enhanced water-rock interactions characterize these waters. Springs from western Uganda show a shift in 18O/16O to higher values as a result of hydrothermal water-rock exchanges. Dissolved ion and noble gas concentrations show potential for use in assessing geothermal energy resources, perhaps aiding the Ugandan Ministry for Energy, Minerals and Development to meet their goal of increasing renewable energy from 4% (current) to 61% of total use by 2017 (Nyakabwa-Atwoki, 2013). Millennium Development Goals Indicators. mdgs.un.org/unsd/mdg/data.aspx Nyakabwa

  10. Cold air incursions, δ18O variability, and monsoon dynamics associated with snow days at Quelccaya Ice Cap, Peru

    Hurley, John V.; Vuille, Mathias; Hardy, Douglas R.; Burns, Stephen J.; Thompson, Lonnie G.

    2015-08-01

    Quelccaya Ice Cap in the Andes of Peru contains an annually resolved δ18O record covering the past 1800 years; yet atmospheric dynamics associated with snow deposition and δ18O variability at this site are poorly understood. Here we make use of 10 years of snow pit and short core δ18O data and hourly snow-height measurements obtained by an automated weather station deployed at the ice cap's summit to analyze linkages between snowfall, δ18O, and the South American summer monsoon (SASM). Snow accumulation peaks in December and is negative May-September. Snow δ18O values decrease gradually through austral summer from about -17 to -24‰. Surface snow δ18O is altered after deposition during austral winter from about -24 to -15‰. More than 70% of the total snow accumulation is tied to convection along the leading edge of cold air incursions of midlatitude air advected equatorward from southern South America. Snowfall amplitude at Quelccaya Ice Cap varies systematically with regional precipitation, atmospheric dynamics, midtroposphere humidity, and water vapor δD. Strongest snowfall gains correspond with positive precipitation anomalies over the western Amazon Basin, increased humidity, and lowered water vapor δD values, consistent with the "amount effect." We discuss ventilation of the monsoon, modulated by midlatitude cold air advection, as potentially diagnostic of the relationship between SASM dynamics and Quelccaya snowfall. Results will serve as a basis for development of a comprehensive isotopic forward model to reconstruct past monsoon dynamics using the ice core δ18O record.

  11. Influence of Interstellar FUV Radiation on the Abundance Ratio of 13CO to C18O in L 1551

    Lin, Sheng-Jun; Shimajiri, Yoshito; Hara, Chihomi; Lai, Shih-Ping; Nakamura, Fumitaka; Sugitani, Koji; Kawabe, Ryohei; Kitamura, Yoshimi; Yoshida, Atsushi; Tatei, Hidefumi; Akashi, Toshiya; Tsukagushi, Takashi

    2015-08-01

    To investigate the relationship between the far-ultraviolet (FUV) radiation and the abundance ratios between 13CO and C18O, we observed L 1551 in 12CO (J=1-0), 13CO (J=1-0) and C18O (J=1-0) using the Nobeyama Radio Observatory 45 m telescope with an angular resolution of ~22" (corresponding to 0.017 pc at a distance of 160 pc). L 1551 is chosen because it is relatively isolated in Taurus-Auriga complex, providing an ideal environment for studying the variation of abundance ratio due to the penetration of the FUV photons. L 1551 is a young star-forming region containing at least 6 young protostars between Class I and Class III stages and a quiescent elongated starless core. The distribution of 12CO emission shows the outflows coming from 2 youngest protostars IRS5 and NE. The 13CO and C18O are detected throughout the whole region with enhancement around the outflows and depletion in the outflow cavities. To avoid the influence of outflows, we exclude the outflow regions for X(13CO)/X(C18O) abundance ratio calculation. X(13CO)/X(C18O) is found in the range of 3.2 -- 36.2 with a mean value of 7.6. Comparing to the extinction map derived from Herschel observations, we found that the abundance ratio reaches its maximum at low AV and decreases to typical solar system value of 5.5 within the starless core. The high X(13CO)/X(C18O) value at the low AV value in L 1551 is most likely due to the selective FUV photodissociation of C18O. This is in contrast with Orion-A region where its internal OB stars keep the abundance ratio at a high level greater than ~10.

  12. LED-based Fourier transform spectroscopy of 16O12C18O and 12C18O2 in the 11,260-11,430 cm-1 range

    Serdyukov, V. I.; Sinitsa, L. N.; Lugovskoi, A. A.; Borkov, Yu. G.; Tashkun, S. A.; Perevalov, V. I.

    2016-07-01

    The absorption spectrum of the 16O12C18O and 12C18O2 carbon dioxide isotopologues has been recorded in the 11,260- 11,430 cm-1 spectral range using Bruker IFS 125 HR Fourier transform spectrometer with resolution 0.05 cm-1 at temperature 297 K and path length 24 m. The 18O enriched sample of carbon dioxide at total pressure 96.5 mbar was used for these purposes. The spectrometer used LED emitter as a light source. This gave possibility to reach the minimal detectable absorption coefficient αmin~1.4×10-7 cm-1 using 23,328 scans. In the recorded spectrum we have assigned the 00051-00001 band for both 16O12C18O and 12C18O2 isotopologues using the predictions performed within the framework of the method of effective operators. The line positions and intensities of the observed bands are found. The comparison of the observed and predicted line positions and intensities is performed confirming good accuracy of the predictions. The spectroscopic parameters for the observed bands are determined.

  13. Differential membrane proteomics using 18O-labeling to identify biomarkers for cholangiocarcinoma

    Kristiansen, Troels Zakarias; Harsha, H C; Grønborg, Mads; Maitra, Anirban; Pandey, Akhilesh

    2008-01-01

    enrichment of cellular subproteomes prior to mass spectrometric analysis can provide increased coverage of certain classes of molecules. We used a membrane protein enrichment strategy coupled with 18O labeling based quantitative proteomics to identify proteins that are highly expressed in cholangiocarcinomas....... In addition to identifying several proteins previously known to be overexpressed in cholangiocarcinoma, we discovered a number of molecules that were previously not associated with cholangiocarcinoma. Using immunoblotting and immunohistochemical labeling of tissue microarrays, we validated Golgi...... membrane protein 1, Annexin IV and Epidermal growth factor receptor pathway substrate 8 (EPS8) as candidate biomarkers for cholangiocarcinomas. Golgi membrane protein 1 was observed to be overexpressed in 89% of cholangiocarcinoma cases analyzed by staining tissue microarrays. In light of recent reports...

  14. Optimised conditions for the synthesis of (17)O and (18)O labelled cholesterol.

    de la Calle Arregui, Celia; Purdie, Jonathan A; Haslam, Catherine A; Law, Robert V; Sanderson, John M

    2016-02-01

    Conditions are described for the preparation of cholesterol with (17)O and (18)O labels from i-cholesteryl methyl ether using minimal amounts of isotopically enriched water. Optimum yields employed trifluoromethanesulfonic acid as catalyst in 1,4-dioxane at room temperature with 5 equivalents of water. An isotopic enrichment >90% of that of the water used for the reaction could be attained. Tetrafluoroboric acid could also be used as catalyst, at the expense of a lower overall reaction yield. Byproducts from the reaction included dicholesteryl ether, methyl cholesteryl ether, compounds formed by ether hydrolysis, and olefins arising from elimination reactions. Reactions in tetrahydrofuran yielded significant amounts of cholesteryl ethers formed by reaction with alcohols arising from hydrolysis of the solvent. PMID:26724708

  15. Two-neutron stripping in ({sup 18}O, {sup 16}O) and (t,p) reactions

    Cavallaro, M.; Agodi, A.; Carbone, D.; Cunsolo, A. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania (Italy); Bondì, M.; Cappuzzello, F.; Nicolosi, D.; Tropea, S. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania, Italy and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Borello-Lewin, T.; Rodrigues, M. R. D. [Instituto de Física - Universidade de São Paulo, Rua do Matão Travessa R Nr.187 CEP 05508-090 Cidade Universitária, São Paulo (Brazil); De Napoli, M. [INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Garcia, V. N. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata, 24210-340, Niteroi, RJ (Brazil); Linares, R.; Lubian, J.; Paes, B. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata , 24210-340, Niteroi, RJ (Brazil); Foti, A. [Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania, Italy and INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy)

    2014-11-11

    The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C reactions has been investigated at 84 MeV incident energy. The charged ejectiles produced in the reaction have been momentum analyzed and identified by the MAGNEX magnetic spectrometer. Q-value spectra have been extracted with an energy resolution of 160 keV (Full Width at Half Maximum) and several known bound and resonant states of {sup 14}C have been identified up to 15 MeV. In particular, excited states with dominant 2p - 4h configuration are the most populated. The absolute values of the cross sections have been extracted showing a striking similarity with those measured for the same transitions by (t,p) reactions. This indicates that the effect of the {sup 16}O core is negligible in the reaction mechanism.

  16. Mean field boson treatment of the electron scattering form factors in 18O

    An extended mean field boson approach to proton-neutron systems with nπ ≠ nν is proposed an applied to calculating the energy spectra as well as the electron scattering form factors for the 0+ → 0+ and 0+ → 2+ transitions in 18O. Provided the single-particle orbitals are taken from the lowest three major oscillator shells and all nucleons are allowed to be active, the agreement with experimental data is very good. The results are also compared with those obtained in the restricted sd-shell subspace, which enables one to estimate the effects of possible excitations of the 16O core. It is found that such effects are non-negligible

  17. Evidence for solar forcing of climate variation from δ18O of peat cellulose

    2000-01-01

    There have been a number of investigations for examining the possible link between long-term climate variability and solar activity.A continuous δ18O record of peat cellulose covering the past 6000 years and the response of climate variation inferred from the proxy record to solar forcing are reported.Results show that during the past 5000 years the abrupt climate variations,including 17 warming and 17 cooling,and a serious of periodicities,such as 86,101,110,127,132,140,155,207,245,311,820 and 1050 years,are strikingly correlative to the changes of solar irradiation and periodicity.These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.

  18. Evidence for solar forcing of climate variation from δ18O of peat cellulose

    洪业汤; 刘东生; 姜洪波; 周立平; 洪冰; 朱泳煊; 李汉鼎; 冷雪天; 秦小光; 王羽; 林庆华; 曾毅强

    2000-01-01

    There have been a number of investigations for examining the possible link between long-term climate variability and solar activity. A continuous δ18O record of peat cellulose covering the past 6 000 years and the response of climate variation inferred from the proxy record to solar forcing are reported. Results show that during the past 5 000 years the abrupt climate variations, including 17 warming and 17 cooling, and a serious of periodicities, such as 86, 101, 110,127, 132, 140, 155, 207, 245, 311, 820 and 1 050 years, are strikingly correlative to the changes of solar irradiation and periodicity. These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.

  19. Origin of summer monsoon rainfall identified by δ18O in precipitation

    PANG Hongxi; HE Yuanqing; ZHANG Zhonglin; LU Aigang; GU Juan; ZHAO Jingdong

    2005-01-01

    A negative correlation between δ18O in monsoon precipitation and f, the ratio of precipitable water in monsoon region to that in water source area, is hypothesized.Using the Rayleigh model, a new method for identifying origin of summer monsoon rainfall is developed based on the hypothesis. In order to validate the method, the isotopic data at New Delhi, a typical station in the southwest monsoon region, and Hong Kong, a typical station in the southeast monsoon region, were collected and analyzed for case studies.The case studies indicate that the water source areas of the monsoon rainfall at the two stations identified by the method are accordant with the general atmosphere circulation patterns. The method developed in this paper is significantly important for tracing the origin of summer monsoon precipitation.

  20. δ18O isotope map-generation of European mineral waters, applications and limits

    There is an increasing demand for independent analytical methods which can control the geographical origin of food. The EU project TRACE was started with the aim to develop a general understanding of the relation of the geo-bio-climatic environment and the isotope and elemental signature in food commodities. Besides mineral water, the agricultural products wheat, honey, olive oil and lamb meat are investigated. As one part of the study a detailed δ18O map for groundwater will be generated by the isotope results of 600 samples of European mineral waters. These groundwater isotope maps provide a multitude of applications not only for authenticity of food, but for groundwater recharge and climate studies, criminal forensics as well as archaeology too. (author)

  1. An explanation for the 18O excess in Noelaerhabdaceae coccolith calcite

    Hermoso, M.; Minoletti, F.; Aloisi, G.; Bonifacie, M.; McClelland, H. L. O.; Labourdette, N.; Renforth, P.; Chaduteau, C.; Rickaby, R. E. M.

    2016-09-01

    Coccoliths have dominated the sedimentary archive in the pelagic environment since the Jurassic. The biominerals produced by the coccolithophores are ideally placed to infer sea surface temperatures from their oxygen isotopic composition, as calcification in this photosynthetic algal group only occurs in the sunlit surface waters. In the present study, we dissect the isotopic mechanisms contributing to the "vital effect", which overprints the oceanic temperatures recorded in coccolith calcite. Applying the passive diffusion model of carbon acquisition by the marine phytoplankton widely used in biogeochemical and palaeoceanographic studies, our results suggest that the oxygen isotope offsets from inorganic calcite in fast dividing species Emiliania huxleyi and Gephyrocapsa oceanica originates from the legacy of assimilated 18O-rich CO2 that induces transient isotopic disequilibrium to the internal dissolved inorganic carbon (DIC) pool. The extent to which this intracellular isotopic disequilibrium is recorded in coccolith calcite (1.5 to +3‰ over a 10 to 25 °C temperature range) is set by the degree of isotopic re-equilibration between CO2 and water molecules before intracellular mineralisation. We show that the extent of re-equilibration is, in turn, set by temperature through both physiological (dynamics of the utilisation of the DIC pool) and thermodynamic (completeness of the re-equilibration of the relative 18O-rich CO2 influx) processes. At the highest temperature, less ambient aqueous CO2 is present for algal growth, and the consequence of carbon limitation is exacerbation of the oxygen isotope vital effect, obliterating the temperature signal. This culture dataset further demonstrates that the vital effect is variable for a given species/morphotype, and depends on the intricate relationship between the environment and the physiology of biomineralising algae.

  2. The First Detailed 2H and 18O Isoscapes of Freshwater in Scotland

    Meier-Augenstein, W.; Hoogewerff, J.; Kemp, H. F.; Frew, D.

    2012-04-01

    Scotland's freshwater lochs and reservoirs provide a vital resource for sustaining biodiversity, agriculture, food production as well as for human consumption. Regular monitoring of freshwater quality by the Scottish Environmental Protection Agency (SEPA) fulfils the legislative requirements but new scientific methods involving stable isotope analysis present an opportunity for delivering on current and nascent government policies [1] and gaining a greater understanding of Scottish waters and their importance in the context of climate change, environmental sustainability and the aforementioned functions. In brief, 2H and 18O isoscapes of Scottish freshwater could be used to support fundamental and applied research in: • Climate change - These first ever isoscapes will provide a baseline against which future environmental impact can be assessed due to changes in the characteristic isotope composition of freshwater lochs and reservoirs. • Scottish branding - Location specific stable isotope signatures of Scottish freshwater have the potential to be used as a tool for provenancing and thus protecting premium Scottish produce such as Scottish beef, Scottish berries and Scottish Whisky. During 2011, freshwater samples were collected with the support of SEPA from more than 80 freshwater lochs and reservoirs across Scotland. Here we present the result of the 2H and 18O stable isotope analyses of these water samples together with the first isoscapes generated based on these data. [1] Adaptation Framework - Adapting Our Ways: Managing Scotland's Climate Risk (2009): Scotland's Biodiversity: It's in Your Hands - A strategy for the conservation and enhancement of biodiversity in Scotland (2005); Recipe For Success - Scotland's National Food and Drink Policy (2009); Scottish Planning Policy Environmental Report (2009); Scottish Planning Policy (SPP) 15 Planning for Rural Development (2005); National Planning Policy Guideline (NPPG) 14: Natural Heritage (1999).

  3. Preferential formation of 13C- 18O bonds in carbonate minerals, estimated using first-principles lattice dynamics

    Schauble, Edwin A.; Ghosh, Prosenjit; Eiler, John M.

    2006-05-01

    Equilibrium constants for internal isotopic exchange reactions of the type: Ca12C18O16O2+Ca13C16O3↔Ca13C18O16O2+Ca12C16O3 for individual CO 32- groups in the carbonate minerals calcite (CaCO 3), aragonite (CaCO 3), dolomite (CaMg(CO 3) 2), magnesite (MgCO 3), witherite (BaCO 3), and nahcolite (NaHCO 3) are calculated using first-principles lattice dynamics. Calculations rely on density functional perturbation theory (DFPT) with norm-conserving planewave pseudopotentials to determine the vibrational frequencies of isotopically substituted crystals. Our results predict an ˜0.4‰ excess of 13C18O16O22- groups in all studied carbonate minerals at room-temperature equilibrium, relative to what would be expected in a stochastic mixture of carbonate isotopologues with the same bulk 13C/ 12C, 18O/ 16O, and 17O/ 16O ratios. The amount of excess 13C18O16O22- decreases with increasing temperature of equilibration, from 0.5‰ at 0 °C to <0.1‰ at 300 °C, suggesting that measurements of multiply substituted isotopologues of carbonate could be used to infer temperatures of ancient carbonate mineral precipitation and alteration events, even where the δ 18O of coexisting fluids is uncertain. The predicted temperature sensitivity of the equilibrium constant is ˜0.003‰/°C at 25 °C. Estimated equilibrium constants for the formation of 13C18O16O22- are remarkably uniform for the variety of minerals studied, suggesting that temperature calibrations will also be applicable to carbonate minerals not studied here without greatly compromising accuracy. A related equilibrium constant for the reaction: Ca12C18O16O2+Ca12C17O16O2↔Ca12C18O17O16O+Ca12C16O3 in calcite indicates formation of 0.1‰ excess 12C 18O 17O 16O 2- at 25 °C. In a conventional phosphoric acid reaction of carbonate to form CO 2 for mass-spectrometric analysis, molecules derived from 13C18O16O22- dominate (˜96%) the mass 47 signal, and 12C 18O 17O 16O 2- contributes most of the remainder (3%). This suggests

  4. The interstellar C18O/C17O ratio in the solar neighbourhood: The rho Oph cloud

    Wouterloot, J G A; Henkel, C

    2004-01-01

    Observations of up to ten carbon monoxide (CO and isotopomers) transitions are presented to study the interstellar C18O/C17O ratio towards 21 positions in the nearby (d~140pc) low-mass star forming cloud rho Oph. A map of the C18O J=1-0 distribution of parts of the cloud is also shown. An average 12C18O/12C17O isotopomeric ratio of 4.11 +/- 0.14, reflecting the 18O/17O isotope ratio, is derived from Large Velocity Gradient (LVG) calculations. From LTE column densities we derive a ratio of 4.17 +/-0.26. These calculations also show that the kinetic temperature decreases from about 30 K in the cloud envelope to about 10 K in the cloud cores. This decrease is accompanied by an increase of the average molecular hydrogen density from 10^4 cm-3 to >10^5 cm-3. Towards some lines of sight C18O optical depths reach values of order unity.

  5. The high-resolution climaterecorded in the δ18O of Porites lutea from the Nansha Islands of China

    2001-01-01

    A Porites lutea core from Yongshu Reef of Nansha Islands covering 50 years growth history was analyzed for oxygen isotopic composition with monthly and seasonally resolution. The calibration of the δ18O with the instrumental temperature indicated that the coral δ18O is a good indicator for sea surface temperature (SST) and air temperature ( t ). It can be used to reconstruct the SST and air temperature of the Yongshu Reef sea area. In addition, the coral δ18O provides signatures for the intensity of the East Asia monsoon and it is a record for the activities of El Ni(n~)o events. With the calibrated SST and air temperature formulas, the most recent fifty years SST and air temperature were reconstructed based on the coral δ18O, thus back up the understanding of the climate of Nansha Islands to 1950, far beyond the limit of the instrumental recording since September 1988. It was found that, in general, increasing 1℃ air temperature results in 0.24‰ decrease in skeletal δ18O.

  6. Correlation between δ18O in precipitation and surface air temperature on different time-scale in China

    The relation between isotopic compositions of precipitation and surface air temperature provides a unique tool for paleoclimate studies, among which the relation between long term changes in δ18O of precipitation and surface air temperature at different stations or in a given location seems to be the most appropriate to paleoclimatic reconstructions. Analysis was conducted on monthly and annual mean δ18O content of precipitation and surface air temperature at spatial and fixed locations by using the data of China (1985-2002) in Global Network of Isotopes in Precipitation (GNIP) Database. This study shows that there is a positive correlation between δ18O of precipitation and surface air temperature for stations located in north of 34 degree-36 degree N latitudes. The seasonal δ18O-temperature gradient derived from the monthly data of 12 stations in northern China is about 0.034% degree C-1. The δ18O-temperature gradient, however, derived from the long term annual mean data of 13 stations, is about 0.052% degree C-1, which is substantially larger than the seasonal gradient. (authors)

  7. δ18O and δ13C Analysis in Tree Rings of Pterocarpus angolensis Growing in Zimbabwe

    McLeran, K.; Schoof, J. T.; Lefticariu, L.; Therrell, M.

    2015-12-01

    Instrumental weather records in southern Africa are largely limited to the last 100 years and documentary weather-related data are rare prior to the 1800s, hindering our understanding of the natural and/or anthropogenic factors that influence climate variability over this region. Measuring stable isotopes ratios (commonly 13C/12C and 18O/16O) in tree rings can provide a good proxy for extending climate data beyond the instrumental record. The objective of this study is to characterize historical variations in the climatology underlying extreme climatic events in Zimbabwe using instrumental climate records (precipitation and temperature) and a multi-proxy approach (ring width, δ18O, and δ13C) for dendroclimatic proxy reconstructions. A 90-year (1900-1990) δ18O and δ13C tree ring record using four Pterocarpus angolensis samples is being developed and compared to tree ring width, monthly, seasonal, and annual precipitation totals, meteoric water δ18O values, and mean monthly and seasonal temperature. Preliminary results indicate significant correlations between the average δ18O record and the previous year December precipitation totals (r=0.41, pZimbabwe.

  8. Incomplete fusion and preequilibrium emission in the reactions 40Ar + 45Sc, 40Ar + 24Mg, 40Ar + 13C at 27.5 MeV by nucleon

    The evaporation residues were detected by means of a heavy ion time of flight system. As an attempt to examine in detail incomplete fusion for medium and light mass systems we have studied the reactions with experimental conditions allowing a complete separation and identification of the final products. We have analysed the velocity of the evaporation residues. The preequilibrium particles appear to be governed by two different regimes. The results show clearly that various compound nuclei are formed in the incomplete fusion process. The 40Ar + 13C reaction appears to be a special case. In the 40Ar+24Mg reaction, the study of preequilibrium particles in coincidence with evaporation residues confirms the results suggested for the heavy fragments

  9. Aplicaciones de los marcadores biogeoquímicos δ13C y δ18O en Mazama temama Aplications of biogeochemical markers δ13C and δ18O in Mazama temama

    Víctor Adrián Pérez-Crespo; Ximena Ulloa-Montemayor; Guillermo Acosta-Ochoa; Joaquín Arroyo-Cabrales; Luis M. Alva-Valdivia; Pedro Morales-Puente; Edith Cienfuegos-Alvarado

    2012-01-01

    Se presentan los valores isotópicos de δ13C y δ18O obtenidos del esmalte dental de un temazate procedente de un sitio arqueológico. Dichos valores indican que este cérvido tenía una dieta ramoneadora y habitaba en una zona de vegetación cerrada.We present isotopic values of δ13C and δ18O obtained from dental enamel in a brocket deer individual found in an archeological site. Those values show that the individual had a browser in an area of closed vegetation.

  10. Determination of ring-oxygen kinetic-isotope effects in methyl-D-xylopyranoside-5-18O

    The analytical procedures are described for measuring oxygen-18 kinetic-isotope effects in the ring oxygen of methyl-α and β-D-xylopyranosides-5-18O. The study was undertaken to confirm one of two possible mechanisms by which D-glycopyranosides undergo hydrolysis, i.e., the A-1 cyclic or acyclic mechanism. Oxygen-18 labeled sugars were subjected to either acid or enzyme hydrolysis. β-D-xylopyranose-5-18O was separated by GLC as a reaction product (5% and 100% hydrolysis) in the form of a t-butyldimethyl silyl ether (BDMS) and monitored for oxygen-18. Combined gas chromatography-mass spectrometry (GC/MS) provided data consistent with an A-1 cyclic mechanism. No significant kinetic-isotope effect (18O. An additional neutron activation analysis (NAA) procedure is presented for monitoring oxygen-18 in sugars. A computer program is included for verifying fragment losses in mass spectra for unenriched compounds

  11. H_2^{16}O and H_2^{18}O Maser Emission from Gas-Dust Clouds

    Nesterenok, Aleksandr; 10.1134/S1063773711070036

    2011-01-01

    The collisional pumping of H_2^{16}O and H_2^{18}O masers in hot dense gas-dust clouds has been simulated numerically. New data on the rate coefficients for collisional transitions from Faure et al. (2007) were used in the calculations. The possibility of detecting H_2^{18}O emission in 22.2-GHz H_2^{16}O maser sources is investigated. The medium is shown to become optically thick in the H_2^{16}O lines for which an inverted level population is observed at H_2O column densities of ~10^{19}-10^{20} cm^{-2}. A simultaneous observation of H_2^{18}O emission and H_2^{16}O maser emission in the same source will allow the physical conditions in the gas-dust cloud to be refined.

  12. Holocene East Asian summer monsoon records in northern China and their inconsistency with Chinese stalagmite δ18O records

    Liu, Jianbao; Chen, Jianhui; Zhang, Xiaojian; Chen, Fahu

    2016-04-01

    Monsoon precipitation over China exhibits large spatial differences. It has been found that a significantly enhanced East Asian summer monsoon (EASM) is characterized by increased rainfall in northern China and by reduced rainfall in southern China, and this relationship occurs on different time scales during the Holocene. This study presents results from a diverse range of proxy paleoclimatic records from northern China where precipitation variability is traditionally considered as an EASM proxy. Our aim is to evaluate the evolution of the EASM during the Holocene and to compare it with all of the published stalagmite δ18O records from the Asian Monsoon region in order to explore the potential mechanism(s) controlling the Chinese stalagmite δ18O. We found that the intensity of the EASM during the Holocene recorded by the traditional EASM proxy of moisture (or precipitation) records from northern China are significantly different from the Chinese stalagmite δ18O records. The EASM maximum occurred during the mid-Holocene, challenging the prevailing view of an early Holocene EASM maximum mainly inferred from stalagmite δ18O records in eastern China. In addition, all of the well-dated Holocene stalagmite δ18O records, covering a broad geographical region, exhibit a remarkably similar trend of variation and are statistically well-correlated on different time scales, thus indicating a common signal. However, in contrast with the clear consistency in the δ18O values in all of the cave records, both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal-to- centennial time scales over eastern China. In addition, both paleoclimatic records and modeling results suggest that Holocene East Asian summer monsoon precipitation reached a maximum at different periods in different regions of China. Thus the stalagmite δ18O records from the EASM region should not be regarded as a reliable indicator of the strength of the East

  13. A new interpretation of the two-step δ18O signal at the Eocene-Oligocene boundary

    H. A. Dijkstra

    2010-07-01

    Full Text Available The most marked step in the global climate transition from "Greenhouse" to "Icehouse" Earth occurred at the Eocene-Oligocene (E–O boundary, 33.7 Ma. Evidence for climatic changes comes from many sources, including the marine benthic δ18O record, showing an increase by 1.2–1.5‰ at this time. This positive excursion is characterised by two steps, separated by a plateau. The increase in δ18O values has been attributed to rapid glaciation of the Antarctic continent, previously ice-free. Simultaneous changes in the δ13C record are indicative of a greenhouse gas control on climate. Previous studies show that a decline in pCO2 beyond a certain threshold value may have initiated the growth of a Southern Hemispheric ice sheet. These studies were not able to conclusively explain the remarkable two-step profile in δ18O. Furthermore, they did not address the potential role of changes in ocean circulation in the E–O transition. Here a new interpretation of the δ18O signal is presented, based on model simulations using a simple coupled 8-box-ocean, 4-box-atmosphere model with an added land ice component. The model was forced with a slowly decreasing atmospheric carbon dioxide concentration. It is argued that the first step in the δ18O represents a shift in meridional overturning circulation from a Southern Ocean to a bipolar source of deep-water formation, which is associated with a cooling of the deep sea. This shift can be initiated by a small density perturbation in the model, although there is also a parameter regime for which the shift occurs spontaneously. The second step in the δ18O profile occurs due to a rapid glaciation of the Antarctic continent. This new interpretation is a robust outcome of our model and is in good agreement with proxy data.

  14. Water budget of Semiadalia undecimnotata Schn. larvae feeding on Myzus persicae Sulz. studied with HT18O

    In coccinella larvae the total uptake was determined in two different ways: (1) from the cumulative water diet measured directly, by aphid consumption, and from the vapour cuticular absorption rate, which was estimated with HTO alone in control experiments; (2) from the elimination rate of double-labelled water, HT18O, initially added to the body water and analysed with a theoretical model. The results obtained from both methods in the 3rd and 4th larval stages are correlated, and it is suggested that double-labelled HT18O may be used to measure aphid consumption in the field. (author)

  15. Latest miocene benthic delta/sup 18/O changes, global ice volume, sea level and the Messinian salinity crisis

    Hodell, D.A.; Elmstrom, K.M.; Kennett, J.P.

    1986-04-03

    Oxygen isotope evidence indicates high but variable delta/sup 18/O values in benthic foraminiferal calcite during the latest Miocene and earliest Pliocene. These high values may represent increases in global ice volume and associated sea-level fall. The delta/sup 18/O record resembles glacial/interglacial cycles, but with only one-third the amplitude of the late Pleistocene signal. This variability may reflect instability in the Antarctic ice sheet, and palaeomagnetic correlation points to an isotopic event coinciding with the isolation and desiccation of the Mediterranean basin during the latest Messinian.

  16. Sub-barrier enhancement of fusion as compared to a microscopic method in 18O+12C

    Steinbach, T. K.; Vadas, J.; Schmidt, J.; Haycraft, C.; Hudan, S.; deSouza, R. T.; Baby, L. T.; Kuvin, S. A.; Wiedenhöver, I.; Umar, A. S.; Oberacker, V. E.

    2014-01-01

    Measurement of the energy dependence of the fusion cross-sec on at sub-barrier energies provides an important test for theoretical models of fusion. To extend the measurement of fusion cross-sections in the sub-barrier domain for the 18O+12C system. Use the new experimental data to confront microscopic calculations of fusion. Evaporation residues produced in fusion of 18O ions with 12C target nuclei were detected with good geometric efficiency and identified by measuring their energy and time...

  17. Variability of the Indo-Pacific warm pool convection since 1867 AD in a tree cellulose δ18O record

    Zhu, M.; Stott, L. D.; Buckley, B. M.

    2011-12-01

    The Indo-Pacific Warm Pool (IPWP) is a major heat and moisture source for atmospheric circulation and is influential for global climate. Various methods, e.g. satellite observations, paleoclimate reconstructions using corals, marine sediments, and speleothems, as well as climate models, have been employed to study the hydrological variability of the IPWP and its relation to global climate. In this study, we provide an alternative way to investigate this problem by analyzing the stable isotopic composition (δ18O) of tree ring cellulose, sampled subannually from Pinus merkusii that grow in Kirirom National Park of southern Cambodia. Our cellulose δ18O record, which spans the period 1867-2006, reveals regular seasonal cycles with an average amplitude of ~4 %, mainly reflecting the seasonal difference in the isotopic composition of soil moisture. The δ18O minimum value in each annual cycle is believed to represent the most isotopically- depleted precipitation of each year, which derives from the oceanic moisture from IPWP in September-October. An isotope amount effect is manifested in the cellulose δ18O minimum values, as they correlate strongly with the amount of rainout over the IPWP before the moisture is transported towards Cambodia. They correlate strongly with the outgoing long wave radiation over the IPWP as well, suggesting that the cellulose δ18O from southern Cambodia could be used to reconstruct the convection intensity over the IPWP. Spectral analysis of the cellulose δ18O reveals significant peaks that are accordant with the ENSO periodicity, 2-7 years, as well as a decadal periodicity of 13.5 years. The variability of our cellulose δ18O record on ENSO band are similar to central Pacific coral δ18O records, with reduced amplitude of variability in the1920sthrough the 1950s, a period of weak ENSO activity. The decadal variability in our cellulose record is also common in coral records, such as the 1976-77 shift, and this might be related to internal

  18. Fluid participation in deep fault zones: Evidence from geological, geochemical, and 18O/16O relations

    Kerrich, R.; La Tour, T. E.; Willmore, L.

    1984-06-01

    Fluid incursion into fault zones and their deeper level counterparts, brittle-ductile shear zones, is examined in a number of different crustal environments. At the Grenville front, translation was accommodated along two mylonite zones and an associated boundary fault. The high- (MZ II) and low-temperature (MZ I) mylonite zones formed at 580 to 640°C and 430 to 490°C, respectively, in the presence of fluids of metamorphic orgin indigenous to the immediate rocks. A population of posttectonic quartz veins occupying brittle fractures were precipitated from fluids with extremely negative δ18O at 200 to 300°C. The water may have been derived from downwards penetration into fault zones of low-18O precipitation on a mountain range induced by continental collision with, uplift accommodated at deep levels by the mylonite zones coupled with rebound on the boundary faults. At Lagoa Real, Brazil, Archaean gneisses overlie Proterozoic sediments along thrust surfaces and contain brittle-ductile shear zones locally occupied by uranium deposits. Following deformation at 500 to 540°C, in the presence of metamorphic fluids and under conditions of low water to rock ratio, shear zones underwent local intense oxidation and desilicification. All minerals undergo a shift of -10‰, indicating discharge of meteoric water recharged formation brines in the underlying Proterozoic sediments up through the Archaean gneisses during overthrusting: about 1000 km3 of solutions passed through these structures. At Yellow-knife, a series of large-scale shear zones developed by brittle-ductile mechanisms, involving volume dilation with migration of ˜5 wt % volatiles into the shear zone from surrounding metabasalts. This early deformation involved no departures in redox state or whole rock δ18O from background states of Fe2+/ΣFe = 0.72 and 7 to 7.5‰, respectively, attesting to conditions of low water/rock. Shear zones subsequently acted as high-permeability conduits for pulsed discharge of >9

  19. Biosynthesis of the meroterpenoid, austin, by Aspergillus ustus: incorporation of 18O2, sodium [1-13C,18O2] acetate, and [Me-13C,2H3] methionine

    Mass spectral and 13C n.m.r. analyses of austin produced by fermentation of Aspergillus ustus in the presence of 18O2 and [Me-13C,2H3]methionine showed that all labelled methionine-derived hydrogens were retained, determined that five of nine oxygens were introduced by aerobic oxidation, and elucidated the general mechanism of late biosynthetic stages. (author)

  20. Planktic δ18O records in the northern South China Sea: MIS 5.5 vs MIS 1

    Sarnthein, M.; Sadatzki, H.

    2012-04-01

    Benthic δ18O records show peak and average levels for Marine Isotope Stage (MIS) 5.5, which are 0.1-0.2 ‰ lighter than during MIS 1, a shift that largely results from changes in global ice volume. In planktic δ18O records of the northern South China Sea this trend may grow by 0.1-0.2 ‰ due to both a rise in sea surface temperatures (SST) during MIS 5.5 and enhanced freshwater input. On the other hand, dominant sources of atmospheric humidity may alter from the far distant equatorial Indian (18O depleted) to the nearby West Pacific Ocean (18O enriched), thus significantly influencing the δ18O value of the monsoon-controlled freshwater discharge to the South China Sea (Pausata et al., 2011), and accordingly, the local planktic δ18O signal of surface waters. We tested the role of these possibly opposed factors by means of planktic δ18O records with centennial-scale resolution at ODP Site 1144 (2040 m w.d.; Bühring et al., 2004) and MD05-2904 (2070 m w.d.; Ge et al., 2010). In contrast to an expected 18O depletion for MIS 5.5 of 0.3 ‰, the pertinent core sections were 18O enriched by 0.4 ‰ as compared to MIS 1. This positive shift may either suggest a major and dominant switch in atmosph¬eric water supply from Indian to nearby West Pacific sources or exhibit a loss of the sediment section crucial for MIS 5.5, that is a distinct stratigraphic gap. Highly resolved δ18O records obtained for comparison from three sediment cores retrieved nearby at much greater water depths (ODP Sites 1145, 1146; Core 17924) clearly show for MIS-5.5 the expected δ18O level that is slightly lighter than that of MIS 1, in harmony with increased SST (He et al., 2008), and thus support the hiatus model. It is also corroborated by large fields of (modern) erosional furrows which are generated by a vigorous inflow of Upper Pacific Deepwater passing along the continental slope off Hong Kong near 2350 m w.d. During interglacial MIS 5.5, this current had probably moved upslope by

  1. The Impact of Clouds on Ecosystem-Atmosphere CO18O Exchanges in the U.S. Great Plains

    Still, C. J.; Riley, W. J.; Biraud, S. C.; Noone, D. C.; Berry, J. A.

    2005-12-01

    The downward excursion in δ18O of atmospheric CO2 observed during the 1990s and the large interannnual variability characteristic of this isotopologue are not understood. We hypothesize that these variations in δ18O of atmospheric CO2 may be linked to global-scale variations in cloud cover and its influence on biosphere-atmosphere CO18O exchanges. Recent work has demonstrated the influence of clouds on canopy photosynthesis through increases in the diffuse radiation fraction and relative humidity, combined with decreases in leaf temperature. In concert, these alterations tend to increase canopy photosynthesis, which should also increase CO18O fluxes. However, photosynthetic CO18O fluxes also depend on the δ18O of leafwater, and enhanced cloudiness should decrease the δ18O of leafwater by enhancing relative humidity. Thus, the net impact of differing cloud cover on biosphere-atmosphere CO18O exchanges is difficult to predict. To capture these contrasting effects, we employed a comprehensive ecosystem isotope model (ISOLSM) in the southern great plains region of Oklahoma and Kansas. This region is particularly amenable for such a study because of the density of cloud property and radiation measurements. The region contains natural and agricultural ecosystems representing a variety of photosynthetic pathways and growth forms, including tallgrass prairie pastures, broadleaf forests, and crops. To drive the model across the entire region, we used Mesonet meteorological data collected at 120 stations in 2004, as well as precipitation δ18O values from the National Atmospheric Deposition Program network. LAI profiles from 2004 were derived from MODIS data. Our results suggest a large impact of clouds on photosynthetic CO2 and CO18O fluxes across this region. In an unstressed broadleaf deciduous forest (LAI=6.3), three sequential midsummer days with contrasting cloud cover illustrate this impact. Julian Day 222 is sunny, JD 223 is partly cloudy, and JD 224 is very

  2. Initial isotopic geochemistry ({delta} 18 O, {delta} D) of fluids from wells of the Los Humeros, Pue., geothermal field; Geoquimica isotopica ({delta} 18 O, {delta} D) inicial de fluidos de pozos del campo geotermico de Los Humeros, Pue.

    Barragan Reyes, Rosa Maria; Arellano Gomez, Victor Manuel [Instituto de Investigaciones Electricas, Gerencia de Geotermia, Cuernavaca, Morelos (Mexico)]. E-mail: rmb@iie.org.mx; Ramirez Montes, Miguel; Tovar Aguado, Rigoberto [Comision Federal de Electricidad, Gerencia de Proyectos Geotermoelectricos, Morelia, Michoacan (Mexico)

    2010-01-15

    Isotopic data ({delta} 18 O, {delta} D) from fluids from production wells at the Los Humeros, Pue., geothermal field were analyzed to investigate the possible origin of these fluids and the dominant processes of the reservoir at its initial state. According to pre-exploitation data, it is suggested the Los Humeros reservoir fluids are made of a mixture of meteoric water of very light isotopic composition (paleo-fluids) and andesitic water. The relationship {delta} D vs {delta} 18 O from pre-exploitation data indicates the produced fluids are composed of a mixture of (at least) two fluids with distinct isotopic compositions. At the more enriched end of the mixing relationship are the isotopic compositions of the wells H-23 and H-18 (located in the southern area of the field), while the lighter fluids were found in well H-16 (originally) and then in well H-16 (repaired). It was found that the liquid phases of deep wells are more enriched in {delta} 18 O while the shallow wells present lower values, suggesting a convection process at the initial state. Based on this isotopic profile, it is considered that even the production depths of the wells H-1, H-12 and H-16 (repaired) are just about the same, but their respective isotopic compositions are quite different. The {delta} 18 O value for well H-16 (repaired) seems to be that of condensate steam, while the corresponding values for wells H-1 and H-12 fall within the value interval of the deep wells (H-23). This suggests wells H-1 and H-12 are collecting very deep fluids enriched in {delta} 18 O. These results could be useful in creating a conceptual model of the reservoir. [Spanish] Se analizaron datos isotopicos ({delta}18 O, {delta}D) de los fluidos de pozos productores del campo geotermico de Los Humeros, Pue., para investigar el posible origen de los fluidos asi como los procesos dominantes del yacimiento en su estado inicial. De acuerdo con datos previos a la explotacion, se plantea que los fluidos del yacimiento

  3. Oxygen determination in materials by 18O(p,αγ)15N nuclear reaction

    Kumar, Sanjiv; Sunitha, Y.; Reddy, G. L. N.; Sukumar, A. A.; Ramana, J. V.; Sarkar, A.; Verma, Rakesh

    2016-07-01

    The paper presents a proton induced γ-ray emission method based on 18O(p,αγ)15N nuclear reaction to determine bulk oxygen in materials. The determination involves the measurement of 5.27 MeV γ-rays emitted following the de-excitation of 15N nuclei. A description of the energetics of the reaction is given to provide an insight into the origin of 5.27 MeV γ-rays. In addition, thick target γ-ray yields and the limits of detection are measured to ascertain the analytical potential of the reaction. The thick-target γ-ray yields are measured with a high purity germanium detector and a bismuth germanate detector at 0° as well as 90° angles in 3.0-4.2 MeV proton energy region. The best limit of detection of about 1.3 at.% is achieved at 4.2 MeV proton energy for measurements at 0° as well 90° angles with the bismuth germanate detector while the uncertainty in quantitative analysis is oxygen in several oxide as well as non-oxide materials.

  4. States of 15C via the (18O,16O) reaction

    Cappuzzello, F; Cunsolo, A; Foti, A; Orrigo, S E A; Rodrigues, M R D; Borello-Lewin, T; Carbone, D; Schillaci, C

    2010-01-01

    A study of the 15C states was pursued in 2008 at the Catania INFN-LNS laboratory by the 13C(18O,16O)15C reaction at 84 MeV incident energy. The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Thanks to an innovative technique the ejectiles were identified without the need of time of flight measurements. Exploiting the large momentum acceptance (25%) and solid angle (50 msr) of the spectrometer, the 15C energy spectra were obtained with a quite relevant yield up to about 20 MeV excitation energy. The application of the powerful technique of the trajectory reconstruction did allow to get an energy resolution of about 250 keV FWHM, limited mainly by straggling effects. The spectra show several known low lying states up to about 7 MeV excitation energy as well as two unknown resonant structures at about 11.4 and 13.5 MeV. The strong excitation of these latter together with the measured width of about 2 MeV FWHM could indicate the presence of collective modes of excitation connec...

  5. The ({sup 18}O, {sup 16}O) reaction as a probe for nuclear spectroscopy

    Cappuzzello, F.; Bondì, M.; Nicolosi, D.; Tropea, S. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania, Italy and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Agodi, A.; Carbone, D.; Cavallaro, M.; Cunsolo, A. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania (Italy); Borello-Lewin, T.; Rodrigues, M. R. D. [Instituto de Física - Universidade de São Paulo, Rua do Matão Travessa R Nr.187, 05508-090 Cidade Universitária, São Paulo (Brazil); De Napoli, M. [INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Linares, R. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata, 24210-340, Niteroi, RJ (Brazil); Foti, A. [Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania, Italy and INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy)

    2014-11-11

    The response of nuclei to the ({sup 18}O, {sup 16}O) two-neutron transfer reaction at 84 MeV incident energy has been systematically studied at the Catania INFN-LNS laboratory. The experiments were performed using several solid targets from light ({sup 9}Be, {sup 11}B, {sup 12,13}C, {sup 16}O, {sup 28}Si) to heavy ones ({sup 58,64}Ni, {sup 120}Sn, {sup 208}Pb). The {sup 16}O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (−10%, +14%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra with energy resolution of about 150 keV and angular distributions with angular resolution better than 0.3°. A common feature observed with light nuclei is the appearance of unknown resonant structures at high excitation energy. The strong population of these latter together with the measured width can reveal the excitation of a collective mode connected with the transfer of a pair.

  6. In folio study of carbonic anhydrase and Rubisco activities in higher C3 plants using 18O and mass spectrometry

    This document studies the effects of a mild water stress and carbonic anhydrase activity by ethoxyzolamide (EZA) on the diffusion of CO2 in leaves, by 18O labelling of O2 and of CO2 associated to mass spectrometry. (A.B.). 5 refs., 2 figs

  7. A coral δ18O record of ENSO driven sea surface salinity variability in Fiji (south -western tropical Pacific)

    Le Bec, Nolwenn; Julliet-Leclerc, Anne; Corrège, Thierry; Blamart, Dominique; Delcroix, Thierry

    2000-12-01

    The role of salinity in the dynamics and thermodynamics of El Niño - Southern Oscillation (ENSO) events is increasingly being investigated. However, instrumental records of salinity are scarce and short in the tropical Pacific, and there is a clear need for a reliable salinity proxy to extend our knowledge of ENSO through time. Here, we present 40 years of δ18O data from a Fiji coral (16°48‧S-177°27‧E). The coral δ18O signal integrates both sea surface temperature (SST) and sea surface salinity (SSS) variations. On a seasonal timescale, δ18O is mainly driven by SST changes whereas on an interannual ENSO timescale, it is almost exclusively affected by SSS variability. Since interannual fluctuations of SSS are rather well correlated to the Southern Oscillation Index in Fiji, coral δ18O can be used to reconstruct paleo-salinity data with some level of confidence. This may help for tracking ENSO influences back in time.

  8. Efficient Total Chemical Synthesis of (13) C=(18) O Isotopomers of Human Insulin for Isotope-Edited FTIR.

    Dhayalan, Balamurugan; Fitzpatrick, Ann; Mandal, Kalyaneswar; Whittaker, Jonathan; Weiss, Michael A; Tokmakoff, Andrei; Kent, Stephen B H

    2016-03-01

    Isotope-edited two-dimensional Fourier transform infrared spectroscopy (2 D FTIR) can potentially provide a unique probe of protein structure and dynamics. However, general methods for the site-specific incorporation of stable (13) C=(18) O labels into the polypeptide backbone of the protein molecule have not yet been established. Here we describe, as a prototype for the incorporation of specific arrays of isotope labels, the total chemical synthesis-via a key ester insulin intermediate-of 97 % enriched [(1-(13) C=(18) O)Phe(B24) ] human insulin: stable-isotope labeled at a single backbone amide carbonyl. The amino acid sequence as well as the positions of the disulfide bonds and the correctly folded structure were unambiguously confirmed by the X-ray crystal structure of the synthetic protein molecule. In vitro assays of the isotope labeled [(1-(13) C=(18) O)Phe(B24) ] human insulin showed that it had full insulin receptor binding activity. Linear and 2 D IR spectra revealed a distinct red-shifted amide I carbonyl band peak at 1595 cm(-1) resulting from the (1-(13) C=(18) O)Phe(B24) backbone label. This work illustrates the utility of chemical synthesis to enable the application of advanced physical methods for the elucidation of the molecular basis of protein function. PMID:26715336

  9. Abraham Reef Stable Isotope Data (delta 13C, delta 18O, delta 14C) for 1635-1957

    National Oceanic and Atmospheric Administration, Department of Commerce — Site: Abraham Reef, 22ó 06'S, 153ó 00'E, Porites australiensus, Radiocarbon (delta 14C) and Stable Isotope (del 18O and del 13C) results from bi-annual samples from...

  10. Use of laser spectroscopy to measure the 13C/12C and 18O/16O compositions of carbonate minerals.

    Barker, Shaun L L; Dipple, Gregory M; Dong, Feng; Baer, Douglas S

    2011-03-15

    The stable carbon and oxygen isotope compositions of carbonate minerals are utilized throughout the earth and environmental sciences for various purposes. Here, we demonstrate the first application of a prototype instrument, based on off-axis integrated cavity output laser spectroscopy, to measure the carbon and oxygen isotope composition of CO(2) gas evolved from the acidification of carbonate minerals. The carbon and oxygen isotope ratios were recorded from absorption spectra of (12)C(16)O(16)O, (13)C(16)O(16)O, and (12)C(16)O(18)O in the near-infrared wavelength region. The instrument was calibrated using CaCO(3) minerals with known δ(13)C(VPDB) and δ(18)O(VSMOW) values, which had been previously calibrated by isotope ratio mass spectrometry relative to the international isotopic standards NBS 18 and NBS 19. Individual analyses are demonstrated to have internal precision (1 SE) of better than 0.15‰ for δ(13)C and 0.6‰ for δ(18)O. Analysis of four carbonate standards of known isotopic composition over 2 months, determined using the original instrumental calibration, indicates that analyses are accurate to better than 0.5‰ for both δ(13)C and δ(18)O without application of standard-sample-standard corrections. PMID:21341717

  11. The use of 18O/ 16O ratios to study the formation and chemical origin of coal

    Dunbar, John; Wilson, A. T.

    1983-08-01

    The 18O /16O ratios of some New Zealand peat, lignite and coal samples were measured and compared with those of various coal precursors (cellulose, lignin and plant resins). The results showed that the major source of oxygen in all cases (except that of high rank coal) was from cellulose with the contribution from lignin and plant resins being insignificant.

  12. The use of 18O/16O ratios to study the formation and chemical origin of coal

    The 18O/16O ratios of some New Zealand peat, lignite and coal samples were measured and compared with those of various coal precursors (cellulose, lignin and plant resins). The results showed that the major source of oxygen in all cases (except that of high rank coal) was from cellulose with the contribution from lignin and plant resins being insignificant. (author)

  13. The evolution of Phanerozoic seawater - Isotope paleothermometry finds consensus on Early Paleozoic warmth and constant seawater δ18O

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

    2015-12-01

    Evolution of metazoan life is closely linked to the Phanerozoic evolution of ocean temperatures and chemistry. Oxygen isotopic evidence for early Phanerozoic paleotemperatures has been equivocal, with decreasing δ18O values with age being interpreted as warmer early oceans, decreasing seawater δ18O with age, or increasing diagenetic alteration in older samples. Here we compare an updated compilation of oxygen isotope data for carbonate and phosphate fossils and microfossils (Grossman, 2012, Geol. Time Scale, Elsevier, 195-220) with a compilation of new and existing clumped isotope data. Importantly, these data are curated based on sample preservation with special consideration given to screening techniques, and tectonic and burial history. Burial history is critical in the preservation of carbonate clumped isotope temperatures in particular, which can undergo reordering in the solid state. We use a model derived for reordering kinetics (Henkes et al., 2014, Geochim. Cosmochim. Acta 139:362-382) to screen clumped isotope data for the effects of solid-state burial alteration. With minor but significant exceptions (Late Cretaceous, Early Triassic), average δ18O values (4 m.y. window, 2 m.y. steps) for post-Devonian brachiopods, belemnites, and foraminifera, representing tropical-subtropical surface ocean conditions, yield average isotopic temperatures below 30°C (assuming a seawater δ18O value [ -1‰ VSMOW] of an "ice-free" world). In contrast, Ordovician to Devonian data show sustained temperatures of 35-40°C. Likewise, isotopic paleotemperatures from conodont apatite, known to be resistant to isotopic exchange, follow the same pattern. Clumped isotope data derived from Paleozoic brachiopod shells that experienced minimal burial (< 100 °C) and <1% reordering according to the taxon-specific clumped isotope reordering model yield typical temperatures of 25-30°C for the Carboniferous, and 35-40°C for the Ordovician-Silurian. Inserting clumped temperatures and

  14. Convenient recycling and reuse of bombarded [18O]H2O for the production and the application of [18F]F−

    The limited availability and the increasing demands of [18O]H2O force the reuse of bombarded [18O]H2O for the production of [18F]F− at least for the purposes of research. Therefore, inorganic and organic contaminants have to be removed from the [18O]H2O after bombardment. We present a simple, effective, easy-handling and reliable method of [18O]H2O purification including oxidation and distillation. The obtained recycled [18O]H2O had comparable quality to commercially distributed [18O]water. This was confirmed by a detailed comparison of produced radionuclides and their activities and the application of [18F]F− for the automated synthesis of [18F]fluspidine. - Highlights: • A reliable recycling procedure of irradiated (bombarded) enriched [18O]H2O is described. • Two methods for the oxidation of organic contaminants followed by low temperature distillation are presented. • The characterisation revealed [18O]H2O with high purity, and the production of [18F]F− and its use in radiosyntheses confirm a high quality of the [18O]H2O for the purposes of research

  15. Clumped Isotope Verification of δ18O-Based Freshwater Mussel Shell Growth Chronology for a High-Resolution Climate and River Discharge Record

    VanPlantinga, A.; Grossman, E. L.; Passey, B. H.; Randklev, C.

    2015-12-01

    Isotope profiles in freshwater mussel shells can be used to reconstruct climate, water source, and river discharge, but problems arise from variable water temperature and δ18O. To resolve this complexity and expand the application of isotope sclerochronology to the study of past river systems, we measured δ18O and Δ47 in two common freshwater mussel species from the Brazos River in Texas. To compare the environmental record with the shell record and develop a sclerochronology, weekly water temperature and δ18O data were collected from the Brazos River near College Station from January 2012 to August 2013. The river data reveal complex, irregular patterns for predicted aragonite δ18O. Comparing δ18O profiles from micromilled transects (70-200 µm increments) of coeval shell growth within and between shells yielded consistent patterns. Shell δ18O can be accurately matched to predicted δ18O, providing a chronology of shell growth. However, without a water temperature and δ18O record, interpreting a sclerochronology would be impossible. Shell Δ47 can potentially provide a seasonal chronology to verify the δ18O sclerochronology, which would be invaluable for the use of δ18O sclerochronology in historical and ancient shells. For Δ47 analyses, samples were taken at 0.5 mm resolution in presumed seasonal dark and light growth bands. Clumped temperatures range between 21 and 35 ± 4˚C (Henkes et al., 2013) and track the river temperature record, supporting the interpreted shell δ18O chronology. Shell Δ47-calculated water δ18O values range from -1.2 to 1.5 ± 0.9‰ and match river δ18O. High-resolution shell δ18O profiles combined with Δ47 temperatures can reconstruct a weekly history of water δ18O, and with the observed river discharge vs. water δ18O relation, produce a qualitative record of river discharge. These analytical techniques applied to a historical Brazos River mussel shell collected prior to dam construction reveal weekly records of

  16. The 18O:16O of dissolved oxygen in rivers and lakes in the Amazon Basin: Determining the ratio of respiration to photosynthesis rates in freshwaters

    The concentration and 18O:16O ratio of dissolved oxygen were measured for 23 rivers and lakes of the Amazon Basin during 1988, 1990, and 1991. With only two exceptions, the rivers and lakes had dissolved oxygen concentrations that were at 20-90% of atmospheric saturation levels. The δ18O of the dissolved oxygen ranged from 15 to 30% (vs. SMOW). The δ18O for the lakes were the lowest at 15-23%. δ18O 18O of the rivers, in contrast, ranged from 24 to 30 per-thousand > 24.2 per-thousand resulted from respiration. Despite this clear difference between the δ18O for rivers and lakes, these water bodies had similar levels of oxygen undersaturation. The δ18O and dissolved oxygen concentrations are used to determine the ratio of community respiration (R) to gross photosynthesis (P) rates. R:P varied between ∼1 and 1.5 for lakes and between 1.5 and 4 for rivers. For all rivers and lakes, the measured δ18O indicated the presence of photosynthetically produced oxygen, with the highest proportion occurring in lakes. The δ18O of dissolved oxygen is a unique tracer of photosynthetic oxygen and provides, through a determination of R:P, a means of quantifying the heterotrophic state of freshwaters. 29 refs., 8 figs., 4 tabs

  17. Stable isotope time-series in mammalian teeth: In situ δ18O from the innermost enamel layer

    Blumenthal, Scott A.; Cerling, Thure E.; Chritz, Kendra L.; Bromage, Timothy G.; Kozdon, Reinhard; Valley, John W.

    2014-01-01

    Stable carbon and oxygen isotope ratios in mammalian tooth enamel are commonly used to understand the diets and environments of modern and fossil animals. Isotope variation during the period of enamel formation can be recovered by intra-tooth microsampling along the direction of growth. However, conventional sampling of the enamel surface provides highly time-averaged records in part due to amelogenesis. We use backscattered electron imaging in the scanning electron microscope (BSE-SEM) to evaluate enamel mineralization in developing teeth from one rodent and two ungulates. Gray levels from BSE-SEM images suggest that the innermost enamel layer, isotopic signal than other layers. We sampled the right maxillary incisor from a woodrat subjected to an experimentally induced water-switch during the period of tooth development, and demonstrate that secondary ion mass spectrometry (SIMS) can be used to obtain δ18O values with 4-5-μm spots from mammalian tooth enamel. We also demonstrate that SIMS can be used to discretely sample the innermost enamel layer, which is too narrow for conventional microdrilling or laser ablation. An abrupt δ18O switch of 16.0‰ was captured in breath CO2, a proxy for body water, while a laser ablation enamel surface intra-tooth profile of the left incisor captured a δ18O range of 12.1‰. The innermost enamel profile captured a δ18O range of 15.7‰, which approaches the full magnitude of δ18O variation in the input signal. This approach will likely be most beneficial in taxa such as large mammalian herbivores, whose teeth are characterized by less rapid mineralization and therefore greater attenuation of the enamel isotope signal.

  18. Fourth interlaboratory comparison exercise for δ2H and δ18O analysis of water samples (WICO2011)

    Complete text of publication follows. The IAEA Isotope Hydrology Laboratory organized the fourth interlaboratory comparison exercise for the analysis of hydrogen and oxygen stable isotope composition of water. Four water samples prepared and calibrated at the IAEA Isotope Hydrology Laboratory were labelled IAEA-OH-13 to IAEA-OH-16. Altogether 137 laboratories from 53 countries submitted 172 datasets to the IAEA. Samples cover the range of δ18O and δ2H values typical of natural waters. Each laboratory received four samples with a randomly assigned identification code. The reference values were calculated from the results of the 12 laboratories whose performance was the best in the last intercomparison exercise, WICO2002 (Table 1). Cumulative deviations for δ18O and δ2H are less than 0.2h and 2.0h, respectively. Statistical analysis of the submitted results was undertaken to assess the performance of each laboratory (precision and accuracy) with respect to the reference δ18O and δ2H values for the analysed four samples by a two-stage statistical treatment adopted in previous IAEA interlaboratory exercises. From our results (Table 2) it is generally seen that the mean values are within uncertainty the same as the reference values, however, our standard deviations are significantly higher. Fig. 1. shows the obtained value of each laboratory for the δ18O of the OH-16 sample and the δ2H value of the OH-14 sample, respectively. Our values are indicated by black arrows. The upper and the lower horizontal black lines show the 1σ deviation of the reference value (middle line). Fig. 2. shows the cumulative deviation of datasets from the reference values determined as 8 x δ18O + δ2H. According to these data, our dataset (black arrow) is the 25th best out of the 172 datasets of 153 laboratories in the world.

  19. A (nearly) complete experimental linelist for 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O by high-sensitivity CW-CRDS spectroscopy between 5851 and 7045 cm-1

    An experimental database for the 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O isotopologues of carbon dioxide has been constructed on the basis of the high-sensitivity absorption spectrum of carbon dioxide with 99% enrichment in 13C recorded by CW-cavity ring down spectroscopy (CW-CRDS) between 5851 and 7045 cm-1. As a result of the achieved sensitivity (typical noise equivalent absorption αmin∼2-5x10-10 cm-1) combined with the high linearity and dynamics (more than four decades) of the CW-CRDS technique, the amount of spectroscopic information contained in these spectra was considerable. A total of 8639 transitions of the 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O isotopologues with line strength as low as 5x10-29 cm/molecule were assigned. They belong to a total of 150 bands, while less than 20 bands were previously reported by Fourier transform spectroscopy. The excellent agreement between the predictions of the effective operators model and the observations has allowed using an automatic search program to assign the weaker lines observed in the congested spectrum. The spectroscopic parameters of the vibrational upper levels were obtained from a fit of the measured line positions. A number of resonance interactions were observed; in particular, several occurrences of interpolyad anharmonic couplings not included in the polyad model of effective Hamiltonian, were found to affect a few bands of the 16O13C18O and 16O13C17O isotopologues. In the list of 8639 transitions, which are provided as Supplementary material, line positions are experimental values (typical uncertainty in the order of 1x10-3 cm-1), while line strengths were calculated at 296 K by using the effective operators approach (typical uncertainty in the order of 5%). In the case of the 13C16O2 isotopologue, the reported transitions represent 99.65% of the total absorbance in the region considered

  20. The 1996 thaw as a {sup 18}O tracer experiment at the lysimeter plant in Wagna; Die Schneeschmelze 1996 als {sup 18}O-Tracerversuch an der Lysimeteranlage in Wagna

    Fank, J.; Zojer, H. [Forschungsgesellschaft Joanneum, Graz (Austria). Inst. fuer Geothermie und Hydrogeologie; Stichler, W. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany). Inst. fuer Hydrologie

    1999-02-01

    In the year 1991 a research site was set up in Wagna in the western Leibnitz Field (Styria) which permits an examination of seepage water movement and of material transport as a function of the permeability of the uppermost soil layers and the underlying more coarsly clastic sediments under locale-specific natural management systems. Research at this site is largely based on hydrochemical and isotope-hydrological analysis. The {sup 18}O isotope is an ideal natural tracer of water movement. Infiltration water from the thaw following a snowy winter was displaced downward into the unsaturated zone as a result of a major precipitation event of 85.5 mm from April 2 to 5, 1996. This displacement is evident in the {sup 18}O concentrations of the seepage water at various measuring depths. The displacement is associated with recharge events, thaw processes tending to produce dispersive flows and precipitation events leading to ``piston flow effects. Winter precipitation water reaches a depth of 60 to 70 cm by mid-April. The attenuated {sup 18}O concentration reveals the predominant flow characteristics in the different compartments of the unsaturated zone (finely clastic soils, gravels, and sands). [Deutsch] Im Jahre 1991 wurde in Wagna, im westlichen Leibnitzer Feld (Steiermark), eine Forschungsstation errichtet, die es erlaubt, unter ortsueblichen, natuerlichen Bewirtschaftungssystemen die Sickerwasserbewegung und den Transport von Stoffen in Abhaengigkeit von der Durchlaessigkeit der obersten Bodenschichten und der darunter folgenden groeberklastischen Sedimente vor allem auf Grundlage der hydrochemischen und isotopenhydrologischen Analytik zu untesuchen. Die Verwendung des {sup 18}O-Isotops als natuerlicher Tracer repraesentiert in idealer Weise die Bewegung des Wassers. Infiltrationswasser aus der Schneeschmelze nach einem schneereichen Winter wurde durch ein starkes Niederschlagsereignis von 85.6 mm zwischen 2. und 5. April 1996 in der ungesaettigten Zone

  1. Analysis of the CRDS spectrum of 18O3 between 6950 and 7125 cm-1

    The absorption spectrum of the 18O3 isotopologue of ozone was recorded by CW-Cavity Ring Down Spectroscopy in the 6950-7125 cm-1 region. The typical noise equivalent absorption of the recordings is αmin ≈1×10-10 cm-1. The spectrum is dominated by three very weak bands: 3ν1+5ν3 near 7009 cm-1 and the ν2+7ν3 and 4ν2+5ν3 interacting bands near 7100 cm-1. In total 260, 206 and 133 transitions were assigned for the 3ν1+5ν3, ν2+7ν3 and 4ν2+5ν3 bands, respectively. The line positions of the 3ν1+5ν3 band were modelled using an effective Hamiltonian (EH) model involving two dark states - (6 0 1) and (2 5 2) - in interaction with the (3 0 5) bright state. The EH model developed for the ν2+7ν3 and 4ν2+5ν3 bands involves only the (0 1 7) and (0 4 5) interacting bright states. Line positions could be reproduced with rms deviations on the order of 0.01 cm-1 and the dipole transition moment parameters were determined for the three observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a list of 984 transitions of the three bands which is provided as Supplementary Material.

  2. Differential cross section measurements of 27Al(p,p/γ)27Al and 27Al(p,αγ)24Mg reactions in the energy range of 1.6-3.0 MeV

    Jokar, A.; Kakuee, O.; Lamehi-Rachti, M.; Sharifzadeh, N.; Fathollahi, V.

    2015-11-01

    In this work measurement of differential cross sections of 27Al(p,p/γ)27Al (Eγ = 844, 1014 keV) and 27Al(p,αγ)24Mg (Eγ = 1369 keV) nuclear reactions in the proton energy range of 1.6-3.0 MeV are described and the measured values are presented. Thin Al target was prepared by evaporating a 26 μg/cm2 Al onto a 129 μg/cm2 self-supporting Ag film. The gamma-rays and backscattered protons were detected simultaneously. The gamma-rays and protons were collected by an HPGe detector placed at an angle of 90° with respect to beam direction and an ion implanted Si detector placed at a scattering angle of 165°, respectively. In this experimental setup the great advantage is that differential cross sections could be independent on absolute values of the collected beam charge. The overall systematic uncertainty of cross sections was estimated to be ±9% while statistical errors were less than ±5%.

  3. Infrared spectroscopy of 17O- and 18O-enriched carbon dioxide: Line positions and intensities in the 4681-5337 cm-1 region

    Borkov, Yu. G.; Jacquemart, D.; Lyulin, O. M.; Tashkun, S. A.; Perevalov, V. I.

    2015-07-01

    The line positions and intensities of carbon dioxide isotopologues have been retrieved in the 4681-5337 cm-1 spectral range from Fourier transform spectra of carbon dioxide recorded in LADIR (Paris, France) with the Bruker IFS 125-HR [Jacquemart D, et al., J Quant Spectrosc Radiat Transf 2012;113:961-975]. In total 6386 line positions and intensities of 89 bands of 12 isotopologues 16O12C16O, 16O13C16O, 16O12C18O, 16O12C17O, 16O13C18O, 16O13C17O, 18O12C18O, 17O12C18O, 17O12C17O, 18O13C18O, 17O13C18O, and 17O13C17O have been retrieved. 23 bands were newly assigned. All studied bands belong to the ΔP=7 series of transitions, where P = 2V1 +V2 + 3V3 is the polyad number (Vi are vibrational quantum numbers). The accuracy of the line position measurement is about 0.3×10-3 cm-1 for the unblended and not very weak lines. The accuracy of the line intensities varies from 4% to 15% depending on the isotopologue, on the intensity of the line and on the extent of the line overlapping. The observed intensities were used to fit the effective dipole moment parameters for the ΔP=7 series of transitions in 16O12C18O, 16O12C17O, 12C17O2, 17O12C18O, 16O13C17O, 13C17O2 and 17O13C18O isotopologues of carbon dioxide.

  4. Assimilation of High 18O/16O Crust by Shergottite-Nakhlite-Chassigny (SNC) Magmas on Mars

    Day, J. M.; Taylor, L. A.; Valley, J. W.; Spicuzza, M. J.

    2005-12-01

    There is significant geochemical evidence for assimilation of crustal material into sub-aerial, mantle-derived, terrestrial basaltic magmas. Some of the most powerful constraints on crustal assimilation come from oxygen isotope studies, because supracrustal rocks often have distinct 18O/16O ratios resulting from interaction with Earth's hydrosphere. From a planetary perspective, studies of carbonate concretions from meteorite ALH84001 have yielded evidence for low-temperature crustal interaction at or near the surface of its putative parent body, Mars. This finding raises the possibility that crustal assimilation processes may be tracked using oxygen isotopes in combination with geochemical data of other reputed martian (SNC) meteorites. The whole-rock oxygen isotope ratios (Laser fluorination δ18O = +4.21 to +5.85‰ VSMOW) of SNC meteorites, correlate with aspects of their incompatible element chemistry. Some of the oxygen isotope variability may be explained by post-magmatic alteration on Mars or Earth; however, it appears, based on petrographic and geochemical observations, that a number of SNC meteorites, especially Shergottites, retain the original whole-rock oxygen isotope values of their magmas prior to crystallisation. Correlations between oxygen isotopes and incompatible element geochemistry are consistent with assimilation of a high-18O/16O, incompatible-element rich, oxidizing crustal component by hot, mantle-derived magmas (δ18O = ~~4.2‰). A crustal component has previously been recognized from Sr-Nd-Os isotope systematics and oxygen fugacity measurements of SNC meteorites. Oxygen isotope evidence from SNC meteorites suggests high-18O/16O crustal contaminants on Mars result from low temperature (< 300°C) interaction with martian hydrosphere. The extent of apparent crustal contamination tracked by oxygen isotopes in SNC meteorites implies that the majority of martian crust may have undergone such interactions. Evidence for assimilation of

  5. Reconstructing relative humidity from plant δ18O and δD as deuterium deviations from the global meteoric water line.

    Cellulose δ18O and δD in preserved plant material can provide insights on climates and hydrological cycling in the distant past. However, most studies of plant cellulose have used only one isotope, most commonly δ18O, resulting in difficulties partitioning variation between chang...

  6. Isotopic tracing (D, 18O and 29Si) to understand the alteration on historic glass

    Verney-Carron, Aurélie; Saheb, Mandana; Valle, Nathalie; Mangin, Denis; Remusat, Laurent; Loisel, Claudine

    2015-04-01

    In order to better preserve historic glasses, e.g. stained glass windows, the understanding of their alteration mechanisms and of what controls the kinetics corresponding to each process is required. The ancient stained glasses are characterized by thick alteration layers, continuous or as pits, that are cracked or lost. Therefore, if a passivating role of the alteration layer has been proved on some other kinds of glass (such as basaltic or nuclear glass) in aqueous medium, the issue can be addressed for low durable stained glass weathered in varying atmospheric conditions. The mechanism of alteration layer formation was first investigated by performing dynamic and static experiments on model medieval glasses altered with a solution doped in 29Si at different concentrations (or saturation degrees). Solid analyses were carried out by SIMS and solution by HR-ICP-MS. Medieval stained glass has mainly a potash-lime-silica composition with a low content in alumina. The alkaline and alkaline-earth elements have thus a modifier role in the glassy network. This structural difference compared to boro- or alumino-silicate glasses could induce differences in the alteration mechanisms. However, the analysis of the Si isotopic signature of the gel layer highlighted that diffusion, but also hydrolysis/condensation reactions, are also involved in the gel layer formation process, leading to a structural and textural reorganization. The second objective was to determine the kinetic role of the alteration layer, and especially to trace the circulation of water once the altered layer is formed. For that, ancient glasses were exposed to simulated rainfall events / drying periods cycles during 3 months by using a solution doped in D and 18O. NanoSIMS analyses have shown that the transport in the alteration layer is mainly driven by diffusion in the porosity despite the presence of cracks that could have been preferential ways of circulation. This demonstrates also a potential

  7. Re—Examination on the Climatological Significance of the Ice Core δ18O Records from No.1 Glacier at the Head of Urumqi River

    侯书贵

    2000-01-01

    Ice core δ18O recorde from the No.a glacier at the head of the Urumqi River were used o characterize the relationship between δ18O and contemporaneous surface air temperature(Ta) nearby the Daxigou Meteorological Station(3539 m above sea level,-2km away from the ice core drilling site),Although the ice core records of annually averaged δ18O are positively correlated with conemporaneous surface air temperature,especially summer air temperature,the correlation is less significant than that for the precipitation samples due to depositional and post-depositional modification processes,However,the Climatological significance of the ice corδ18O records can be still preserved to a certain degree,which moght extend the application of high altitude and sub-tropical ice core δ18O records to paleoclimate reconstruction.

  8. Climatic significance of δ18O records from an 80.36 m ice core in the East Rongbuk Glacier, Mount Qomolangma (Everest)

    ZHANG; Dongqi; QIN; Dahe; HOU; Shugui; KANG; Shichang; REN

    2005-01-01

    The δ18O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ18O and the net accumulation records of the ice core suggests the "amount effect" of summer precipitation on the δ18O values in the region. Therefore, the δ18O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ18O values during strong monsoon phases and higher values during weak phases.

  9. H/D and 16O/18O isotope effects in water permeation process with phase transition

    H/D and 16O/18O isotope effects of water permeation with phase transition have been determined and their mechanism discussed. The special designed and build laboratory installation has been used for experiments. The isotope effects of permeation have been compared with isotope effects of vaporization. It has been found out that H/D effect of permeation exceeds the vapour pressure effect 1.5 times while the 16O/18O effect of permeation was 7 times as large as vapour pressure effect. The cascade installation for water enrichment in D2O and H218O has been also designed. It has been proved that permeation method on hydrophobic membranes could be competitive for the other methods used for D2O and H218O production on industrial scale

  10. 13C/12C and 18O/16O in calcium carbonate-cemented beach sands ('beach rocks')

    A study of the stable isotope composition (C13/C12 and O18/O16) of the cement and the local groundwater in Itaparica Island (Salvador-Brazil) is carried out to determine the origin of the carbonate cement. For area A, the cement has Δ13C = 9% showing that CO2 in groundwater charged by decay of organic material is the source of carbonate in the cement. Probably comentation occurs during loss of excess CO2 from groundwater as comes into an environment where loss of CO2 is possible . In area B, where the cements contain, on the average Δ18O v=1,3%, the cement is formed from carbonate typical of sea water or a mixture of sea water and fresh water. (Autor)

  11. Fourier transform measurements of H218O and HD18O in the spectral range 1000-2300 cm-1

    The spectra of water vapor enriched by 18O were recorded in the 1000-2300 cm-1 spectral range, which corresponds to the spectral region studied by IASI instrument (Infrared Atmospheric Sounding Spectrometer) instrument. The spectra were recorded by a step by step Fourier Transform Spectrometer (FTS) at room temperature with absorption path lengths up to 36 m. Positions, intensities and self broadening coefficients of about 1800 lines of H218O and 900 of HD18O were analyzed and all the transitions were assigned. This paper focuses on lines intensities and comparisons with data from literature are presented. An average difference of 10% with HITRAN2008 database H218O line intensities is found with a maximum discrepancy of about 25% for the ν1-ν2 band.

  12. Separation of radium in the reaction of 60 MeV/u 18O with ThO2

    230Ra and its daughter 230Ac were produced by the reaction of 60 MeV/u 18O with ThO2. Using 133Ba, 224Ra and 212Pb-212Bi as tracers, 0.1M NH4EDTA-0.3M NH4-acetate solution as eluent, the relationship between pH and elution peaks, and the influence of the amount of Ba2+ carrier on the elution curve in cation exchange procedures were tested. Based on the results of conditional experiments, a procedure suitable for isolation of radium from the ThO2 irradiated with 60 MeV/u 18O beam was developed. The results demonstrated that the decontamination effectiveness for main reaction products, specially for barium, was satisfactory. (author)

  13. Integrated platform with a combination of online digestion and (18)O labeling for proteome quantification via an immobilized trypsin microreactor.

    Zhang, Shen; Yuan, Huiming; Zhao, Baofeng; Zhou, Yuan; Jiang, Hao; Zhang, Lihua; Liang, Zhen; Zhang, Yukui

    2015-08-01

    A novel automated integrated platform for quantitative proteome analysis was established with a combination of online digestion of proteins and in situ(18)O labeling by an immobilized enzyme reactor (IMER); digests were captured and desalted by a C18 trap column, and peptides were analyzed by nanoRPLC-ESI-MS/MS. Bovine serum albumin (BSA) was used to evaluate the performance of the developed platform. Compared with traditional offline methods, not only the digestion and labeling time was shortened from 36 h to just 1 h, but also the labeling efficiency was improved from 95% to 99%. Furthermore, the back-exchange from (18)O to (16)O could also be efficiently avoided by the use of IMER. The platform was further evaluated by the quantitative analysis of 100 ng (18)O and (16)O online labeled yeast sample with a mixing ratio of 1 : 1, and the results showed significantly improved sensitivity and reproducibility, as well as improved quantitative accuracy than offline method. With these advantages, the integrated platform was finally applied to the quantitative profiling of 100 ng proteins extracted from two mouse hepatocarcinoma ascites syngeneic cell lines with high and low lymph node metastases rates, and ten differentially expressed proteins were successfully found, most of which were related to tumorigenesis and tumor metastasis. All these results demonstrate that the developed integrated platform can provide a new way for high efficiency (18)O labeling and the quantitative analysis of trace amounts of sample with high accuracy and high reproducibility. PMID:26063120

  14. Selective Memory: Process-Based Temperature Calibration for Greenland Ice Core δ-18O Accounting for Seasonal Biases

    Rhines, A. N.; Huybers, P. J.

    2013-12-01

    Greenland δ-18O variability --- a proxy of temperature variability --- differs markedly between the Holocene and the last glacial. Placing the observed modern temperature record in the context of the past requires an understanding of how temperature variability projects onto the isotopic fractionation and depositional processes that influence the recorded isotopic signal. We apply a new statistical methodology for determining moisture sources to the Greenland ice sheet with model simulations of the Holocene and last glacial. The method uses Lagrangian estimates of source properties, and is validated against conservative Eulerian 'water tagging' tracers. Both the seasonality and source of precipitation change significantly between the Holocene and last glacial, though source temperature is generally stable --- deriving from the near the sea ice edge and being near freezing as this is the most proximate source of water vapor for Greenland. With greater sea ice extent and enhanced orographic forcing, the North Atlantic storm track also migrates southward, reducing the flux of moist static energy to Greenland. This causes a decrease in winter temperature concomitant with a reduced ratio of winter-to-summer accumulation, muting the annual-mean isotopic response to the cooling. Based on these results, a temperature calibration is derived for Greenland δ-18O that depends on the mean background climate and takes into account changes in seasonality and source. The new calibration compares favorably with independent estimates of the δ-18O-temperature relationship from the last glacial and Holocene. These results help to better calibrate the Greenland ice core δ-18O-temperature relationship and provide insight into the difference between modern and glacial climates.

  15. Temporal variation of 18O and deuterium excess in precipitation, river and spring waters in Alpine regions of Switzerland

    The paper presents results of combined 18O and 2H analyses of precipitation, river and spring water samples collected from 1983 to 1992 in the Alpine region of Switzerland. The data obtained prove that there is a good correlation between the surface air temperature and the monthly mean 18O content in precipitation, river and spring waters of the study area. The observed δ 18O temperature coefficient ranges from about 0.8 to 0.9 per mille per deg. C. These results are consistent with values derived from the IARA/WMO Environmental Isotopes in Precipitation Network. During the observation period the deuterium excess dex (dex = δ2H - 8δ18O) in precipitation at stations along a north-south cross-section over the Alps showed a seasonal variation and an apparent altitude effect. At Locarno (370 m a.s.l.), a distinct minimum of about 7.5 per mille occurred in July and a maximum of 12 per mille in September. At the stations Kleine Scheidegg (2060 m a.s.l.) and Saentis (2500 m a.s.l.), the annual mean deuterium excess was generally higher than at Locarno. The maximum value of 13.5 per mille was found to occur in October/November at the Saentis station. The long term trend of the deuterium excess was studied in precipitation and spring waters of the Kleine Scheidegg region. The results obtained suggest a slight decrease of this parameter from 1983 to 1992. In the paper the experimental results are discussed with respect to the potential of the deuterium excess in climate related studies. (author). 10 refs, 6 figs

  16. Multipolarity analysis for 14C high-energy resonance populated by (18O,16O) two-neutron transfer reaction

    The 12C(18O,16O)14C reaction at 84 MeV incident energy has been explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed at 16.9 MeV. A multipolarity analysis of the cross section angular distribution indicates an L = 0 character for such a transition

  17. Temperature evolution from the δ18O record of Hani peat, Northeast China, in the last 14000 years

    HONG Bing; LIU CongQiang; LIN QingHua; Shibata YASUYUKI; LENG XueTian; WANG Yu; ZHU YongXuan; HONG YeTang

    2009-01-01

    From the last deglaclation to the Holocene, the Greenland Ice Core (GISP2) δ18O records as well as the records of ice-rafted debris on the surface of the North Atlantic have revealed a succession of sudden cooling events on the centennial to millennial scales. However, the temperature proxy records are rarely studied systematically and directly to ensure that this air temperature cooling pattern simulta- neously existed in the East Asian Region, in addition to the repeated pattern occurring in the Greater Atlantic Region. A peat cellulose δ18O temperature proxy record proximately existing for 14000 years was picked up from the Hani peat in Jilin Province, China. It suggests by comparison that the sudden cooling events, such as the Older Dryas, Inter-Aller(o)d, Younger Dryas, and nine ice-rafted debris events of the North Atlantic, are almost entirely reiterated in the temperature signals of Hani peat cellulose δ18O. These cooling events show that the repeatedly occurring temperature cooling pattern not only appeared in the North Atlantic Region in the high latitudes, but also in the Northwest Pacific Region in the middle latitudes. The climate change events marking the start of the Holocene Epoch, the Holocene Megathermal, the "8.2 kyr" event, the "4.2 kyr" event, the Medieval Warm Period, and the Little Ice Age are further discussed. The sensitivity response of Hani peat cellulose δ18O to the land surface tem- perature and the reason for the age accuracy of peat cellulose 14C are also discussed based on the characteristics of the peat bog environment.

  18. Temperature evolution from the δ 18O record of Hani peat, Northeast China, in the last 14000 years

    Shibata; YASUYUKI

    2009-01-01

    From the last deglaciation to the Holocene, the Greenland Ice Core (GISP2) δ 18O records as well as the records of ice-rafted debris on the surface of the North Atlantic have revealed a succession of sudden cooling events on the centennial to millennial scales. However, the temperature proxy records are rarely studied systematically and directly to ensure that this air temperature cooling pattern simultaneously existed in the East Asian Region, in addition to the repeated pattern occurring in the Greater Atlantic Region. A peat cellulose δ 18O temperature proxy record proximately existing for 14000 years was picked up from the Hani peat in Jilin Province, China. It suggests by comparison that the sudden cooling events, such as the Older Dryas, Inter-Allerφd, Younger Dryas, and nine ice-rafted debris events of the North Atlantic, are almost entirely reiterated in the temperature signals of Hani peat cellulose δ 18O. These cooling events show that the repeatedly occurring temperature cooling pattern not only appeared in the North Atlantic Region in the high latitudes, but also in the Northwest Pacific Region in the middle latitudes. The climate change events marking the start of the Holocene Epoch, the Holocene Megathermal, the "8.2 kyr" event, the "4.2 kyr" event, the Medieval Warm Period, and the Little Ice Age are further discussed. The sensitivity response of Hani peat cellulose δ 18O to the land surface temperature and the reason for the age accuracy of peat cellulose 14C are also discussed based on the characteristics of the peat bog environment.

  19. Search for the two-photon decay of the 2+ first excited states in 18O and 28Si

    The present work describes an attempt to measure the probability for the two-photon transition between two adjacent nuclear states in the presence of an allowed, strongly predominant one-photon decay, using the Heidelberg-Darmstadt Crystal Ball Spectrometer. The branching ratios of the two-photon decay of the first excited, 2+ levels of 18O and 28Si relative to the one-photon, E2 transitions to the 0+ ground states were determined to be: Wγγ/Wγ = (0.7±2.4) x 10-6 for the 2+>0+ transition in 18O and Wγγ/Wγ = (1.6±1.8) x 10-6 for the 2+>0+ transition in 28Si. Since both results are consistent with zero, it is possible to express them as the upper limits for the two-photon decay (3 δ) of 7.9 x 10-6 of 18O and 6.9 x 10-6 of 28Si 2+ levels. These values are by far the smallest ones reported to be observed in a two-photon decay of a nuclear state. For 18O, the result disproves theoretical estimates of the corresponding two-photon E1F1 matrix element was well as experimental values deduced from multiple-Coulomb-excitation measurements. The main experimental difficulties were caused by the gamma rays from one-photon transitions and were found to be connected with cross-talk events due to Bremsstrahlung of Compton electrons and not - as generally believed - positron annihilation in flight. (orig.)

  20. Radiochemical separation of thorium from the natural uranium irradiated by 60 MeV/u 18O ions

    The experimental conditions for the extraction of thorium by using PMBP as extractant and 234Th as tracer in the nitric acid solution were investigated. Based on the experiments, a chemical procedure used for rapidly separating thorium from the natural uranium irradiated by 18O ions was developed. The γ spectrum of the thorium fraction shows that the most of the reaction products, especially U, Ce and I can be completely removed by using the procedure

  1. Potential utility of tree ring δ18O series for reconstructing precipitation records from the lower reaches of the Yangtze River, southeast China

    Xu, Chenxi; Ge, Junyi; Nakatsuka, Takeshi; Yi, Liang; Zheng, Huaizhou; Sano, Masaki

    2016-04-01

    In this study, we investigated the interannual and intraannual variabilities in the oxygen isotope composition (δ18O) preserved in the tree ring cellulose of Pinus taiwanensis in the lower reaches of the Yangtze River, southeast China, to explore its potential utility for precipitation reconstruction over the period of 1855-2013. Intraannual variations of tree ring cellulose δ18O show distinct annual cycles that are characterized by δ18O maxima in the early growth near the ring boundary and δ18O minima in the middle and late portions of the ring. Seasonal patterns of tree ring δ18O were influenced by August-October typhoons. The tree ring cellulose δ18O was measured in both young and old trees to test for the juvenile effect. The results revealed no significant differences in the mean values and long-term trends in δ18O in the old and young trees. A response analysis indicated that tree ring δ18O correlated significantly with precipitation and relative humidity between May and October, and the δ18O chronology accounted for 37.4% of the actual variation in the May-October precipitation between 1951 and 2013. The extremely dry and wet years revealed by the tree ring δ18O-based reconstructed precipitation also corresponded to actual local drought and flood events from the documentary records. Reconstructed precipitation showed significant relationship with central tropical Pacific sea surface temperature, which indicated that El Niño-Southern Oscillation (ENSO) exerted influences on May-October precipitation in the lower reaches of the Yangtze River. In addition, the relationship between ENSO and precipitation weakened between 1920 and 1940, and low variance of ENSO from 1920 to 1940 may result in the damped ENSO's influences on precipitation in southeast China.

  2. Factors Influencing the Stable Oxygen and Hydrogen Isotopic Composition (δ 18O and δ D) of a Subarctic Freshwater Lake Ecosystem

    Wang, Y.; Wooller, M. J.

    2005-12-01

    Previous studies have shown that the stable oxygen and hydrogen isotopic compositions (δ 18O and δD) in various animal tissues can be used to examine past climates and animal migration pattern. Little attention has been paid to the relative roles of diet and water influencing the overall δ 18O and δD of animal tissues in freshwater ecosystems. It is unclear whether different trophic levels in a freshwater lake ecosystem have an identical relationship to the water that surrounds them. The δ18O and δD values of animal tissues may be controlled by numerous different factors, including metabolic and biosynthetic isotopic fractionation and variations of δ 18O and δD in the food available. We began to examine these issues by analyzing the δ 18O and δD throughout a freshwater aquatic ecosystem at Smith Lake in Alaska. We collected samples representing primary producers and consumers (primary and secondary). Samples included green algae, various aquatic plants, such as Nuphar variegatum (water lily), Polygonum amphibium (water smartweed), Carex utriculata (sedge), Utricularia vulgaris (common bladderwort), Typha latifolia (common cattail), and a range of aquatic invertebrates, including Chironomus. sp (midge), Zygoptera (damselfly), Anisoptera (dragonfly), Dytiscidae (diving beetle) and Euhirudinea (leeches). The δ 18O and δD of Smith Lake water were ~-13.5e and -129.0e, respectively, and we present the δ 18O and δD of the rest of the ecosystem relative to these data. For instance, the δ 18O of chironomus sp. was ~12.1, which is greater than the of the lake water. Preliminary results suggest the extent of the fractionation between δ 18O of chironomids vs. lake water δ 18O is consistent with previous studies. Our data provide an insight into the range of variations that could be expected within a single freshwater ecosystem.

  3. 12CO, 13CO and C18O observations along the major axes of nearby bright infrared galaxies

    Tan, Qinghua; Zhang, Zhiyu; Xia, Xiaoyang

    2011-01-01

    We present simultaneous observations of CO,13CO and C18O J=1-0 emission in 11 nearby (cz<1000 km/s) bright infrared galaxies. Both 12CO and 13CO are detected in the centers of all galaxies, except for 13CO in NGC 3031. We have also detected C18O, CS J=2-1, and HCO+ J=1-0 emission in the nuclear regions of M82 and M51. These are the first systematical extragalactic detections of 12CO and its isotopes from the PMO 14m telescope. We have conducted half-beam spacing mapping of M82 over an area of 4'*2.5' and major axis mapping of NGC 3627, NGC 3628, NGC 4631, and M51. The radial distributions of 12CO and 13CO in NGC 3627, NGC 3628, and M51 can be well fitted by an exponential profile. The 12CO/13CO intensity ratio,R,decreases monotonically with galactocentric radius in all mapped sources. The average R in the center and disk of the galaxies are 9.9+/-3.0 and 5.6+/-1.9 respectively, much lower than the peculiar R(~24) found in the center of M82. The intensity ratios of 13CO/C18O, 13CO/HCO+ and 13CO/CS (either o...

  4. Isotopic analyses (18O, 13C, 14C) of two meromictic lakes in the Canadian Arctic Archipelago

    Meromictic Lakes Garrow and Sophia in the Canadian Arctic Archipelago were sampled to establish the origin and age of their water by isotopic studies. 18O values reflect the permanent stratification of the water in both lakes. The mixolimnia contain waters with an isotopic signal between -13.16 and -21.98%, coherent with the values for precipitation in these high latitudes. In the chemoclines, the delta18O values increase to -10% concomitantly with a rise in chloride content to 42 g.liter-1. In the monimolimnia, hypersaline waters (up to 2.5 times the salinity of seawater) show negative delta18O values (ca. -.08%). These waters result from brine production during permafrost growth in the watershed, according to a Rayleigh process. 14C dating of total inorganic carbon in the Lake Garrow monimolimnion gave an age of 2580 +/- 260 years BP. In Lake Sophia, the deep waters exhibit recent 14C activity that suggests recent infiltration of seawater into the lake basin

  5. Compound-specific delta18O analyses of neutral sugars in soils using GC-Py-IRMS

    Zech, Michael; Glaser, Bruno; Werner, Roland; Juchelka, Dieter

    2010-05-01

    Stable oxygen isotopes (delta18O) are a valuable (paleo-)climate proxy applied to ice cores, deep sea sediments, speleothems and lake sediments. For instance, there has been made much effort to assess delta18O of cellulose from lake sediments. However, purity grade of the extracted cellulose and hygroscopy are analytical problems. In order to overcome these problems, we tested compound-specific delta18O analyses of neutral sugars using gas chromatography - pyrolysis - isotope ratio mass spectrometry (GC-Py-IRMS). Although this technique is available for about the last ten years, it is hardly applied so far. We ensured quantitative conversion of organically bound oxygen to CO in the pyrolysis reactor by monitoring not only mass 28 but also mass 44 (CO2) and excluded oxygen contamination in our system by co-analysing oxygen-free compounds (alkanes). Neutral sugars from litter and topsoils were extracted hydrolytically and measured after derivatization with methylboronic acid (MBA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Corrections were made using sugar standards measured in alternation with the samples to ensure the ‘principle of identical treatment' and for the hydrolytically introduced and exchangeable carbonyl-oxygen bound to C1 in the alditose sugar molecules. First results are promising for the hemicellulose-derived sugars arabinose and xylose as well as for the microbial-derived sugars fucose and rhamnose. Ongoing work focuses on assessing also cellulose-derived glucose and on the analytical elimination of the carbonyl-oxygen of the sugars.

  6. Advances in processes for PET radiotracer synthesis: Separation of [18F]fluoride from enriched [18O]water

    Positron emission tomography (PET) is a powerful scientific and clinical tool for the study and visualization of human physiology that can provide important information about metabolism and diseases such as cancer. At present, [18F]fluorodeoxyglucose ([18F]FDG) is the most frequently used radiotracer for the routine clinical evaluation of malignant tumors in a range of body tissues. FDG synthesis is continuously being developed to improve and simplify the synthetic procedure including the isolation of [18F]fluoride from [18O]water. There are many methods reported in literature for the isolation of [18F]fluoride, including evaporation, coat-capture–elution, the use of cation-exchange resin and electrode trapping. This review article gives an overview of some of the most common methods for the separation of [18F]fluoride ions from [18O]water, highlighting the potential strength of the methods and also problems and weaknesses for synthesis of 18F PET tracers. - Highlights: • New developments in processing of [18F]fluoride from [18O]water are detailed. • Efficient separation is required for dose-on-demand radiopharmaceuticals. • Electrode trapping of [18F]fluoride offers significant advantages for solvent exchange. • Microfluidic devices complement novel technologies for isotope separation and synthesis

  7. Toward accurate thermochemistry of the {sup 24}MgH, {sup 25}MgH, and {sup 26}MgH molecules at elevated temperatures: Corrections due to unbound states

    Szidarovszky, Tamás [MTA-ELTE Research Group on Complex Chemical Systems, P.O. Box 32, H-1518 Budapest 112 (Hungary); Császár, Attila G., E-mail: csaszar@chem.elte.hu [MTA-ELTE Research Group on Complex Chemical Systems, P.O. Box 32, H-1518 Budapest 112 (Hungary); Laboratory on Molecular Structure and Dynamics, Institute of Chemistry, Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest (Hungary)

    2015-01-07

    The total partition functions Q(T) and their first two moments Q{sup ′}(T) and Q{sup ″}(T), together with the isobaric heat capacities C{sub p}(T), are computed a priori for three major MgH isotopologues on the temperature range of T = 100–3000 K using the recent highly accurate potential energy curve, spin-rotation, and non-adiabatic correction functions of Henderson et al. [J. Phys. Chem. A 117, 13373 (2013)]. Nuclear motion computations are carried out on the ground electronic state to determine the (ro)vibrational energy levels and the scattering phase shifts. The effect of resonance states is found to be significant above about 1000 K and it increases with temperature. Even very short-lived states, due to their relatively large number, have significant contributions to Q(T) at elevated temperatures. The contribution of scattering states is around one fourth of that of resonance states but opposite in sign. Uncertainty estimates are given for the possible error sources, suggesting that all computed thermochemical properties have an accuracy better than 0.005% up to 1200 K. Between 1200 and 2500 K, the uncertainties can rise to around 0.1%, while between 2500 K and 3000 K, a further increase to 0.5% might be observed for Q{sup ″}(T) and C{sub p}(T), principally due to the neglect of excited electronic states. The accurate thermochemical data determined are presented in the supplementary material for the three isotopologues of {sup 24}MgH, {sup 25}MgH, and {sup 26}MgH at 1 K increments. These data, which differ significantly from older standard data, should prove useful for astronomical models incorporating thermodynamic properties of these species.

  8. Southwest U.S. Paleoclimate Over the Past 30,000 Years: Insights from Speleothem δ18O and Growth Rate Time Series

    Meyer, K. J.; FENG, W.; Banner, J. L.; James, E.; Musgrove, M.

    2011-12-01

    A 30 ky growth rate and high-resolution δ18O time series from a central Texas (TX) speleothem provides new insights when integrated with recently published speleothem δ18O and growth rate records from New Mexico (NM) and Arizona (AZ), along with Gulf of Mexico (GOM) foraminifera δ18O records. This comparison enables a regional assessment of factors which may control temporal variations in rainfall amount and moisture sources in the Southwestern U.S. The three speleothem locations (TX, NM, AZ) span ~ 1,200 km. A regional east-to-west decrease in speleothem δ18O values of up to 9 % is observed throughout the record. This is the same direction of regional decrease as in modern rainfall. This suggests 1) mixing of moisture from two sources, Pacific moisture (low δ18O), and GOM moisture (high δ18O), and 2) that these two sources have contributed moisture to the region for most of the last 30 ky. Prior to 15 ka, relatively large magnitude, millennial-scale oscillations (up to ~3 %) occur in the NM δ18O record while the TX and AZ records show smaller variations (~1 %). Starting at ~ 15 ka, both AZ and NM records show a rapid increase in δ18O values, whereas TX shows a decrease prior to a rapid increase. This dip in the TX δ18O record approximately corresponds with δ18O shifts in the GOM that have been attributed to glacial melt water inputs. All three records show peaks in growth rate between 15 and 12 ka, and significant decreases in growth rate in the Holocene. The speleothem δ18O time series appear to reflect changes in rainfall amount and composition. The correspondence of the TX and GOM records implicates GOM moisture composition as the major control on Late Pleistocene to Holocene TX precipitation δ18O values. NM and AZ, by contrast, apparently received varying proportions of Pacific and GOM sources over this time period. Periods of high δ18O values in the NM and AZ records, when combined with relative high growth rates, may suggest increased overall

  9. Changes in the δ18O and δ30Si values of partially dissolved phytoliths: implications for environmental reconstruction

    Prentice, A. J.; Jabeen, I.; Webb, E. A.

    2014-12-01

    The oxygen and silicon isotope compositions of phytolith silica preserved in soils can be used to examine past climate and biogeochemical cycles. The δ18O values of phytoliths vary with temperature and the δ18O values of formation water while the δ30Si values of phytoliths depend on silicon availability and weathering rates. However, further investigation into the stability of opal-A phytoliths in soils is necessary, as post-depositional alteration of biogenic silica may alter the isotopic composition and affect paleoenvironmental reconstruction. The effects of partial dissolution on the oxygen- and silicon-isotope composition of phytoliths was assessed through dissolution experiments in silicic acid-free water at a range of temperature (4-44°C) and pH conditions (4-10). After 3-30% dissolution, concurrent oxygen and silicon isotope analyses were obtained for the remaining opal-A. Over the course of the experiments oxygen and silicon isotope values of solid silica changed by up to +4.4 ‰ and +0.55 ‰, respectively. Under most conditions δ30Si values increased during early dissolution, followed by a decrease as dissolution progressed until δ30Si values were similar to, or in extreme cases, lower than the original unaltered phytoliths. This might indicate that both dissolution and re-precipitation contribute to the isotopic composition of the altered phytoliths. Changes in δ18O values of the phytoliths follow a similar pattern. We propose that the outer, reactive surface of a fresh phytolith is depleted of 30Si and 18O relative to the rest of the sample. A decrease in surface area suggests that removal of this layer accounts for the initial increase in δ30Si and δ18O values during early dissolution. Extended reaction times result in lower isotopic values and an unexpected decease in aqueous Si suggesting precipitation or exchange occurs. This study improves our understanding of the role of terrestrial biogenic silica in global Si cycle. Post

  10. Intercomparison of 20th century tropical climate model hindcasts and coral δ18O data using a forward proxy model

    Thompson, D. M.; Evans, M. N.; Ault, T. R.; Cole, J. E.; Emile-Geay, J.

    2009-12-01

    Forward modeling of climate proxies enables identification of uncertainties in the interpretation of high resolution proxy archives in a manner that is complementary to classical inverse methods. By coupling proxy models to climate model output driven with realistic external forcings, a framework for assessment of their consistency with proxy observations over long timescales is created. Here we model reef coral oxygen isotopic composition (δ18O) as a function of sea-surface temperature (SST) and sea-surface salinity (SSS), the latter a linear proxy for the isotopic composition of seawater in the tropics. We first validate this model against a comprehensive network of 20th century coral δ18O measurements. When driven with historical SST and SSS data for the last ~50 years, the forward model is able to capture the spatial and temporal pattern of ENSO variability observed in the corals better than a univariate SST-based model, hence establishing the skill of this bivariate model. We then drive the forward model with SST and SSS from 20th-century simulations of state-of-the-art climate models, such as GFDL CM2.0 (run 1 c3m; Delworth et al, 2006, Wittenberg et al, 2006), to assess the ability of climate models to reproduce tropical climate variability. GFDL CM2.0 forward modeled coral δ18O accurately reproduces the spatio-temporal pattern of the observed coral δ18O trend over the 20th century, and furthermore suggests the trend was primarily driven by increased SSTs. However, the magnitude of the modeled trend is smaller than observed in the corals, suggesting that coral physiology has reacted in a non-linear fashion to the observed climatic forcing, or that GFDL CM2.0's tropical response to external climate forcing is too small. Instead, variance in GFDL modeled corals is dominated by strong interannual variability that is much greater than that observed in corals. The temporal evolution of modeled ENSO variance and frequency over the 20th century is also markedly

  11. High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm-1: Part III-Analysis and theoretical modeling of the 12C17O2, 16O12C17O, 17O12C18O, 16O13C17O and 17O13C18O spectra

    Karlovets, E V; Mondelain, D; Kassi, S; Tashkun, S A; Perevalov, V I

    2014-01-01

    More than 19,700 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990 cm-1 (1.71-1.43 \\mum). This third and last report is devoted to the analysis of the bands of five 17O containing isotopologues present at very low concentration in the studied spectra: 16O12C17O, 17O12C18O, 16O13C17O, 17O13C18O and 12C17O2 (627, 728, 637, 738 and 727 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 1759, 1786, 335, 273 and 551 transitions belonging to 24, 24, 5, 4 and 7 bands were rovibrationally assigned for 627, 728, 637, 738 and 727, respectively. For comparison, only five bands were previously measured in the region for the 728 species. All the identified bands belong to the \\deltaP=8 and 9 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational qua...

  12. Water - Isotope - Map (δ 18O, δ 2H, 3H) of Austria: Applications, Extremes and Trends

    Wyhlidal, Stefan; Kralik, Martin; Benischke, Ralf; Leis, Albrecht; Philippitsch, Rudolf

    2016-04-01

    The isotopic ratios of oxygen and hydrogen in water (2H/1H and 18O/16O) are important tools to characterise waters and their cycles. This starts in the atmosphere as rain or snow and continues in surface water and ends in shallow groundwater as well as in deep groundwater. Tritium formed by natural cosmic radiation in the upper atmosphere and in the last century by tests of thermonuclear bombs in the atmosphere, is characterised by its radioactive decay with a half-life of 12.32 years and is an ideal age-marker during the last 60 years. To determine the origin and mean age of waters in many projects concerning water supply, engineering and scientific projects in the last 45 years on more than 1,350 sites, more than 40,000 isotope measurements were performed in Austria. The median value of all sites of oxygen-18 is δ 18O -10.7 ‰ and for hydrogen-2 δ 2H -75 ‰. As the fractionation is mainly temperature dependent the lowest negative values are observed in winter precipitation (oxygen-18 as low as δ 18O -23 ‰) and in springs in the mountain regions (δ 18O -15.1 ‰). In contrast the highest values were observed in summer precipitation (up to δ 18O - 0.5 ‰) and in shallow lakes in the Seewinkel (up to δ 18O + 5 ‰). The isotopic ratios of the Austrian waters are also influenced by the origin of the evaporated water masses. Therefore the precipitation in the region south of the main Alpine crest (East-Tyrol, Carinthia and South-East Styria) is approximately 1 ‰ higher in δ 18O-values than sites at the same altitude in the northern part. This is most probably caused by the stronger influence of precipitation from the mediterranean area. The median value of all 1,120 sampling sites of decay corrected (2015) tritium measurements is 6.2 tritium units (TU). This is somewhat smaller than the median value of all precipitation stations with 7.2 TU. This can be explained by the fact that in most cases in groundwater the median value has been reduced by decay

  13. Temporal variations of the 18O/16O signal of the whole-canopy transpiration in a temperate forest

    Lee, Xuhui; Kim, Kyounghee; Smith, Ronald

    2007-09-01

    Biosphere-atmosphere exchange of water vapor isotopes plays an important role in the global atmospheric 18O-CO2 and 18O-O2 budgets. In this paper, we report the results of the first continuous measurements of isotope ratios of water vapor and the evapotranspiration flux in a temperate forest over one full growing season. We found that the 18O/16O isotopic signal of the whole-canopy transpiration (δT) was not in steady state with respect to plant source water. The departure from steady state was greatest at night and on days of low transpiration rates. Relative humidity was an important driver on timescales shorter than a few hours; on the diurnal timescale, the nonsteady state behavior was driven by relative humidity and the covarying transpiration rate. On average, δT was lowest in midmorning and highest at midnight, with an average peak-to-peak variation on the order of 15‰ over the growing season. A diurnal variation of 60‰ or more was observed on some days. On the seasonal timescale, δT was tightly coupled with the precipitation isotope ratio in the early growing season and fluctuated around the isotope ratio of the stem water of overstory trees in the late growing season. The temporal shift suggests that the forest switched its water source from the shallow to the deep soil pool and that the overstory trees dominated the whole stand transpiration in the late growing season. Using isotopic partitioning, we estimated that the overstory trees contributed roughly 70% to the whole-stand transpiration water loss during the growing season.

  14. Protostellar accretion traced with chemistry. Comparing synthetic C18O maps of embedded protostars to real observations

    Frimann, S.; Jørgensen, J. K.; Padoan, P.; Haugbølle, T.

    2016-03-01

    Context. Understanding how protostars accrete their mass is a central question of star formation. One aspect of this is trying to understand whether the time evolution of accretion rates in deeply embedded objects is best characterised by a smooth decline from early to late stages or by intermittent bursts of high accretion. Aims: We create synthetic observations of deeply embedded protostars in a large numerical simulation of a molecular cloud, which are compared directly to real observations. The goal is to compare episodic accretion events in the simulation to observations and to test the methodology used for analysing the observations. Methods: Simple freeze-out and sublimation chemistry is added to the simulation, and synthetic C18O line cubes are created for a large number of simulated protostars. The spatial extent of C18O is measured for the simulated protostars and compared directly to a sample of 16 deeply embedded protostars observed with the Submillimeter Array. If CO is distributed over a larger area than predicted based on the protostellar luminosity, it may indicate that the luminosity has been higher in the past and that CO is still in the process of refreezing. Results: Approximately 1% of the protostars in the simulation show extended C18O emission, as opposed to approximately 50% in the observations, indicating that the magnitude and frequency of episodic accretion events in the simulation is too low relative to observations. The protostellar accretion rates in the simulation are primarily modulated by infall from the larger scales of the molecular cloud, and do not include any disk physics. The discrepancy between simulation and observations is taken as support for the necessity of disks, even in deeply embedded objects, to produce episodic accretion events of sufficient frequency and amplitude.

  15. Holocene changes in monsoon precipitation in the Andes of NE Peru based on δ18O speleothem records

    Bustamante, M. G.; Cruz, F. W.; Vuille, M.; Apaéstegui, J.; Strikis, N.; Panizo, G.; Novello, F. V.; Deininger, M.; Sifeddine, A.; Cheng, H.; Moquet, J. S.; Guyot, J. L.; Santos, R. V.; Segura, H.; Edwards, R. L.

    2016-08-01

    Two well-dated δ18O-speleothem records from Shatuca cave, situated on the northeastern flank of the Peruvian Andes (1960 m asl) were used to reconstruct high-resolution changes in precipitation during the Holocene in the South American Summer Monsoon region (SASM). The records show that precipitation increased gradually throughout the Holocene in parallel with the austral summer insolation trend modulated by the precession cycle. Additionally the Shatuca speleothem record shows several hydroclimatic changes on both longer- and shorter-term time scales, some of which have not been described in previous paleoclimatic reconstructions from the Andean region. Such climate episodes, marked by negative excursions in the Shatuca δ18O record were logged at 9.7-9.5, 9.2, 8.4, 8.1, 5.0, 4.1, 3.5, 3.0, 2.5, 2.1 and 1.5 ka b2k, and related to abrupt multi-decadal events in the SASM. Some of these events were likely associated with changes in sea surface temperatures (SST) during Bond events in the North Atlantic region. On longer time scales, the low δ18O values reported between 5.1-5.0, 3.5-3.0 and 1.5 ka b2k were contemporaneous with periods of increased sediment influx at Lake Pallcacocha in the Andes of Ecuador, suggesting that the late Holocene intensification of the monsoon recorded at Shatuca site may also have affected high altitudes of the equatorial Andes further north. Numerous episodes of low SASM intensity (dry events) were recorded by the Shatuca record during the Holocene, in particular at 10.2, 9.8, 9.3, 6.5, 5.1, 4.9, 2.5 and 2.3 ka b2k, some of them were synchronous with dry periods in previous Andean records.

  16. Comparison of coral δ18O with pseudocorals derived from in situ sea surface salinity and temperature measurements

    DeLong, K. L.; Chaichi, N.; Maupin, C. R.; Richey, J. N.; Quinn, T. M.; Poore, R. Z.

    2015-12-01

    Paleoclimatologists use pseudocorals and forward modeling of coral oxygen isotopes (δ18O) to assess δ18O variations for comparison with climate model output in order to understand past tropical oceanic-atmospheric variability. Oxygen isotopic (δ18Ocoral) variability in shallow water coral skeletons is dependent on sea surface temperature (SST) and δ18O of seawater (δ18Osw), which varies with sea surface salinity (SSS). However, measurements of δ18Osw and SSS are sparse; therefore, simulated SSS (e.g., SODA) is typically used in pseudocoral investigations. Our study site is the Dry Tortugas National Park (DRTO; 24º42'N, 82º48'W) in the southeastern Gulf of Mexico (GOM) where hourly SST and SSS measurements are available from NOAA buoys (1992-2002) and the Florida Keys National Marine Sanctuary (FKNMS; 2011-2014). Here we use bivariate forward modeling of monthly average buoy SSS and SST to develop a time series of pseudocoral δ18O (δ18Op = -0.22(‰/ºC)SST + 0.11(‰/psu)SSS) for DRTO that are compared with δ18Ocoral variations from three Siderastrea siderea coral colonies growing in close proximity within the park. We use the relationship for δ18Osw and SSS determined for Flower Garden Banks coral reef in the northern GOM (27º52'N, 93º49'W) since no measurements of δ18Osw are currently available for DRTO. δ18Op co-varies with δ18Ocoral (r2 = 0.59) with a root mean square error (RMSE = 0.32‰) greater than the intercolony δ18Ocoral variability (r2 = 0.80; RSME = 0.07‰). Discrepancies between δ18Op and δ18Ocoral may be related to the lack of a local SSS-δ18Osw relationship for DRTO or uncertainties in subannual time assignment for δ18Ocoral. A new source of SSS is the NASA satellite Aquarius (2012-2014), which may be useful in future pseudocoral studies, that is evaluated along with high resolution simulated SSS (Global Ocean Physics Reanalysis GLORYS2V3; 1993-2012). We find similar correlation between Aquarius-derived SSS and FKNMS SSS (r2

  17. First results of the isotopic study (18O, 2H, 3H) of the Douala Quaternary aquifer (Cameroon)

    The Quaternary sandy aquifer of the Douala sedimentary basin generally shows homogeneous isotopic abundances (18O, 2H, 3H) of water sampled at different depths.The large majority of these samples indicated a direct and fast infiltration of precipitation, without significant evaporation. This homogeneity can moreover be accentuated under the pumping effects, connecting various levels of the multilayer aquifer. These results show that pollution from the surface can quickly reach the deeper layers, and seems to corroborate those obtained on the basis of field measurements and chemical analyses. (author)

  18. The application of δ18O and δD for understanding water pools and fluxes in a Typha marsh

    Bijoor, NS; Pataki, DE; Rocha, AV; Goulden, ML

    2011-01-01

    The δ18O and δD composition of water pools (leaf, root, standing water and soil water) and fluxes [transpiration (T), evaporation (E)] were used to understand ecohydrological processes in a managed Typha latifolia L. freshwater marsh. We observed isotopic steady-state T and deep rooting in Typha. The isotopic mass balance of marsh standing water showed that E accounted for 3% of the total water loss, T accounted for 17% and subsurface drainage (D) accounted for the majority (80%). There was a...

  19. First results of the isotopic study (18O, 2H, 3H) of the Douala Quaternary aquifer (Cameroon)

    The quaternary sandy aquifer of the Douala sedimentary basin generally indicates homogeneity in isotopic abundance (18O, 2H, 3H) of water sampled at different depths. The large majority of these samples indicated a direct and fast infiltration of the precipitations, without significant evaporation. This homogeneity can moreover be accentuated under the pumping effects, putting in communication various levels of the multilayer aquifer. These results show that pollution from the surface can quickly reach the deeper layers, and seems to corroborate those obtained on the basis of field measurements and chemical analyses. (author)

  20. VizieR Online Data Catalog: C18O/C17O ratios in the Galactic center

    Zhang, J. S.; Sun, L. L.; Riquelme, D.; Henkel, C.; Lu, D. R.; Zhang, Y.; Wang, J. Z.; Wang, M.; Li, J.

    2015-09-01

    Our mapping observations of the J=1-0 lines of 12CO, 13 and C17O were carried out with the DLH 13.7m telescope of the Purple Mountain Observatory (PMO) at Delingha in 2011 January and 2012 May and November. The C18O and C17O lines were also observed in single-point mode toward Sgr B2 with the IRAM 30m telescope in 2011 September, and toward Sgr C and Sgr D with the Mopra 22m in 2014 June. (2 data files).

  1. Determination of Isotopic Abundance of 2H, 13C, 18O, and 37Cl in Biofield Energy Treated Dichlorophenol Isomers

    Mahendra Kumar Trivedi

    2015-01-01

    2,4-Dichlorophenol (2,4-DCP) and 2,6-dichlorophenol (2,6-DCP) are two isomers of dichlorophenols, have been used as preservative agents for wood, paints, vegetable fibers and as intermediates in the production of pharmaceuticals and dyes. The aim of the study was to evaluate the impact of biofield energy treatment on the isotopic abundance ratios of 2H/1H or 13C/12C, and 18O/16O or 37Cl/35Cl, in dichlorophenol isomers using gas chromatography-mass spectrometry (GC-MS). The 2,4- DCP and 2,6-DC...

  2. First measurement of the {sup 18}O(p,{alpha}){sup 15}N cross section at astrophysical energies

    Cognata, M La; Spitaleri, C; Cherubini, S; Gulino, M; Lamia, L; Pizzone, R G; Puglia, S M R; Rapisarda, G G; Romano, S; Sergi, M L [INFN Laboratori Nazionali del Sud, Catania (Italy); Mukhamedzhanov, A; Tribble, R E; Al-Abdullah, T; Banu, A; Goldberg, V [Cyclotron Institute, Texas A and M University, College Station, TX (United States); Coc, A [CSNSM, CNRS/IN2P3, Universite Paris Sud, Orsay (France); Irgaziev, B [GIK Institute of Engineering Sciences and Technology, Topi, District Swabi, N. W. F. P. (Pakistan); Kiss, G G [ATOMKI, Debrecen (Hungary); Mrazek, J [Nuclear Physics Institute of ASCR, Rez near Prague (Czech Republic); Crucilla, V, E-mail: LaCognata@lns.infn.i

    2010-01-01

    The {sup 18}O(p,{alpha}){sup 15}N reaction rate has been deduced by means of the Trojan horse method. For the first time the contribution of the 20 keV resonance has been directly evaluated, giving a value about 35% larger than the one in the literature. Moreover, the present approach has allowed to improve the accuracy by a factor 8.5, as it is based on the measured strength instead of spectroscopic measurements. The contribution of the 90 keV resonance has been also determined, which turned out to be of negligible importance to astrophysics.

  3. High sensitivity CW-CRDS of 18O enriched water near 1.6 μm

    The absorption spectrum of 18O enriched water has been recorded by continuous wave cavity ring down spectroscopy between 5905.7 and 6725.7 cm-1 using a series of fibred DFB lasers. The investigated spectral region corresponds to the important 1.55 μm transparency window of the atmosphere where water absorption is very weak. The typical CRDS sensitivity (noise equivalent absorption of 5x10-10 cm-1) allowed for the detection of lines with intensity as low as 10-28 cm/molecule while the minimum intensity value provided by HITRAN in the considered spectral region is 1.7x10-24 cm/molecule. The line parameters were retrieved with the help of an interactive least squares multi-lines fitting program assuming a Voigt function as line profile. Overall, 4510 absorption lines belonging to the H218O, H216O, HD18O, HD16O and H217O water isotopologues were measured. Their intensities range between 3x10-29 and 5x10-23 cm/molecule at 296 K and the typical accuracy on the line positions is 1x10-3 cm-1. 2074 of the observed lines attributed to H218O, HD18O and H217O are reported for the first time. The transitions were assigned on the basis of variational calculations resulting in 288, 135 and 38 newly determined rovibrational energy levels for the H218O, HD18O and H217O isotopologues, respectively. The new data set includes the band origin of the 4ν2 bending overtone of H218O at 6110.4239 cm-1 and rovibrational levels corresponding to J and Ka values up to 18 and 12, respectively, for the strongest bands of H218O: 4ν2, ν1+2ν2, 2ν2+ν3, 2ν1, ν1+ν3, and ν2+ν3. The obtained experimental results have been compared to the spectroscopic parameters provided by the HITRAN database and to the recent IUPAC critical review of the rovibrational spectrum of H218O and H217O as well as to variational calculations. Large discrepancies between the 4ν2 variationally predicted and experimental intensities have been evidenced for the H218O and H216O molecules.

  4. Evaporation induced 18O and 13C enrichment in lake systems: A global perspective on hydrologic balance effects

    Horton, Travis W.; Defliese, William F.; Tripati, Aradhna K.; Oze, Christopher

    2016-01-01

    Growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time. One of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions. However, endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined. As a consequence, isotopic researchers are often required to assume values for multiple parameters, including temperature of carbonate formation or lake water δ18O, in order to interpret changes in hydrologic conditions. Here, we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions. Through integration of multiple large datasets we show that lake carbonate δ18O values and the lake waters from which they are derived are often shifted by >+10‰ relative to source waters discharging into the lake. The global pattern of δ18O and δ13C covariation observed in >70% of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records. Modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where δ18O and δ13C covariation is absent. Aridisol pedogenic carbonates show similar isotopic responses to evaporation, and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed. Recent advances in stable isotope research techniques present unprecedented

  5. Spatial and temporal characteristics of 2H and 18O in the basin of Dongting Lake. Impact of monsoon precipitation

    Two water sampling campaigns were carried out in April and August 2012 to investigate the spatial and temporal characteristics of 2H and 18O in the basin of Dongting Lake and to further understand the interactions between precipitation, river water, lake water, and groundwater. Influenced by different monsoons, precipitation, river water, and lake water are enriched in isotopes in April but depleted in August. Stable isotopes of river water and lake water also have great spatial variations. Unlike river and lake water, groundwater has little seasonal isotopic variation, indicating that the transformation between surface water and groundwater is very slow. (author)

  6. Periodicity analysis of δ18O in precipitation over Central Europe: Time-frequency considerations of the isotopic 'temperature' effect

    Salamalikis, V.; Argiriou, A. A.; Dotsika, E.

    2016-03-01

    In this paper the periodic patterns of the isotopic composition of precipitation (δ18O) for 22 stations located around Central Europe are investigated through sinusoidal models and wavelet analysis over a 23 years period (1980/01-2002/12). The seasonal distribution of δ18O follows the temporal variability of air temperature providing seasonal amplitudes ranging from 0.94‰ to 4.47‰; the monthly isotopic maximum is observed in July. The isotopic amplitude reflects the geographical dependencies of the isotopic composition of precipitation providing higher values when moving inland. In order to describe the dominant oscillation modes included in δ18O time series, the Morlet Continuous Wavelet Transform is evaluated. The main periodicity is represented at 12-months (annual periodicity) where the wavelet power is mainly concentrated. Stations (i.e. Cuxhaven, Trier, etc.) with limited seasonal isotopic effect provide sparse wavelet power areas at the annual periodicity mode explaining the fact that precipitation has a complex isotopic fingerprint that cannot be examined solely by the seasonality effect. Since temperature is the main contributor of the isotopic variability in mid-latitudes, the isotope-temperature effect is also investigated. The isotope-temperature slope ranges from 0.11‰/°C to 0.47‰/°C with steeper values observed at the southernmost stations of the study area. Bivariate wavelet analysis is applied in order to determine the correlation and the slope of the δ18O - temperature relationship over the time-frequency plane. High coherencies are detected at the annual periodicity mode. The time-frequency slope is calculated at the annual periodicity mode ranging from 0.45‰/°C to 0.83‰/°C with higher values at stations that show a more distinguishable seasonal isotopic behavior. Generally the slope fluctuates around a mean value but in certain cases (sites with low seasonal effect) abrupt slope changes are derived and the slope becomes

  7. 18O isotopic characterisation of non-point source contributed heavy metals (Zn and Cu) contamination of groundwater

    In many urbanised areas, fast depletion and severe degradation of the of groundwater resource with contaminants such as nitrate, fluoride, and heavy metals is a common phenomenon, resulting in zonal disparity in fresh water availability. Therefore, for protection of groundwater from pollution and depletion, it is a matter of concern for the planners and decision makers to clearly characterise the sources of contamination and to search for an alternative approach for groundwater development and management. In this context, a new approach is presented here, based on monitoring of 18O stable isotopic and heavy metals composition of groundwater, to clearly characterise non-point source contributed heavy metals pollution of groundwater in northern parts of Delhi area. In the investigated area, the Cu content in the groundwater ranges from 3-41 μg/l and Zn content ranges from 5-182 μg/l, showing considerable variation from location to location as well as within the small parts of a location. Wide variation in the 18O stable isotope content of groundwater (δ value of -5.7 per mille to -8.5 per mille) is due to significant variation in the δ18O-contents of rainfall with space and time, as well as intensity and distribution of rainfall. Enrichment in 18O composition with increasing Cu and Zn levels in groundwater suggest that infiltration of rain water, irrigation water and surface run-off water from the surrounding farm lands, along with agrochemicals and other salts present in the soil, to be the main processes causing groundwater contamination. The concentration of Cu and Zn in groundwater vary spatially, due to different degrees of evaporation/recharge, amounts of fertiliser applied and wastes disposed, adsorption/dispersion of species in the soils and lateral mixing of groundwater. Two opposite mechanisms adsorption and redistribution of infiltrating water along with Zn and Cu species in the soil zone are likely to affect the movement of the Zn and Cu species

  8. A 6-yr record of stable isotope ratios of hydrogen and oxygen and temperature correlation of δ18O in precipitation from Eastern Hungary

    Complete text of publication follows. Investigation of past environmental changes might be possible only if we understand the isotopic systematic of modern precipitation using precipitation-linked stable isotope proxies or models. The apparent temperature coefficient Δδ18O/ΔT is important because it is used to calculate some paleotemperature changes, and because it is a basis for validating the accuracy of GCMs. In principle, three relationships can be observed between the isotopic composition of precipitation and local surface air temperature: (1) a spatial relation between the long-term averages of δ18O (δ2H) of precipitation and the local air temperature for different stations; (2) a temporal relation between short-term (seasonal) changes of δ18O (δ2H) and temperature for a single station or group of stations and (3) a temporal relation between long-term changes in δ18O (δ2H) and temperature at a certain location. The isotopic composition of hydrogen and oxygen of the monthly precipitation from Eastern Hungary was analyzed in samples collected during a monitoring period from the beginning of 2001 to the end of 2006. At the same time an event-based sample collection and data analysis were also performed. During the studied period, the δ18O values varied from 3.9 to -21.3 per mille and the δ2H values from 2.0 to -176.3 per mille. The composite monthly isotopic ratios of oxygen and hydrogen yield a regression line δ2H = 6.9δ18O - 4.1 per mille with a correlation coefficient of 0.92, while the LMWL calculated on event-based sample δ2H and δ18O values gives a regression line δ2H = 6.6δ18O - 9.1 per mille with a correlation coefficient of 0.90. Both lines are close to the GMWL but show the effect of secondary evaporation. The highest δ2H and δ18O values were obtained during the summer months, whereas the lowest δ2H and δ18O values were recorded during autumn and winter. Time series of δ2H and δ18O values for individual samples, amount

  9. Mean proloculus size, delta super(13) C and delta super(18) O variations in recent benthic foraminifera from the west coast of India and their climatic implications

    Nigam, R.; Sarkar, A.

    variabilities in delta super(18) O and delta super(13) C are rather high which may be due to disequilibrium isotopic fractionation or probably partial selection of specimens. Climatic implications of the results are discussed and few recommendations are also...

  10. Large-Scale Multiplexed Quantitative Discovery Proteomics Enabled by the Use of an 18O-Labeled “Universal” Reference Sample

    Qian, Wei-Jun; Liu, Tao; Petyuk, Vladislav A; Gritsenko, Marina A.; Petritis, Brianne O.; Polpitiya, Ashoka D.; Kaushal, Amit; Xiao, Wenzhong; Finnerty, Celeste C.; Jeschke, Marc G.; Jaitly, Navdeep; Monroe, Matthew E.; Moore, Ronald J.; Moldawer, Lyle L; Davis, Ronald W

    2009-01-01

    The quantitative comparison of protein abundances across a large number of biological or patient samples represents an important proteomics challenge that needs to be addressed for proteomics discovery applications. Herein, we describe a strategy that incorporates a stable isotope 18O-labeled ″universal″ reference sample as a comprehensive set of internal standards for analyzing large sample sets quantitatively. As a pooled sample, the 18O-labeled ″universal″ reference sample is spiked into e...

  11. The comparison of H$_2$CO (1$_{10}$--1$_{11}$), C$^{18}$O (1--0) and continuum towards molecular clouds

    Di Tang, Xin; Zhou, Jian Jun; Wu, Gang; Okoh, Daniel

    2014-01-01

    We present large scale observations of C$^{18}$O (1--0) towards four massive star forming regions for MON R2, S156, DR17/L906 and M17/M18. The transitions of H$_2$CO (1$_{10}$--1$_{11}$), C$^{18}$O (1--0) and 6 cm continuum were compared towards the four regions. Analysis of observation and Non--LTE model results shows that the brightness temperature of the formaldehyde absorption line is strongest in background continuum temperature range of about 3 -- 8 K. The excitation of the H$_2$CO absorption line is affected by strong background continuum emission. From the comparison of H$_2$CO and C$^{18}$O maps, we found that the extent of H$_2$CO absorption is broader than that of C$^{18}$O emission in the four regions. Except for the DR17 region, the H$_2$CO absorption maximum is located at the same position with the C$^{18}$O peak. The good correlation between intensities and widths of H$_2$CO absorption and C$^{18}$O emission lines indicate that the H$_2$CO absorption line can trace dense and warm regions of the...

  12. Strong coupling of centennial-scale changes of Asian monsoon and soil processes derived from stalagmite δ18O and δ13C records, southern China

    Liu, Dianbing; Wang, Yongjin; Cheng, Hai; Edwards, R. Lawrence; Kong, Xinggong; Li, Ting-Yong

    2016-05-01

    The paleoclimate application of speleothem δ13C is influenced by site-specific processes. Here we present four stalagmite δ13C records from two caves in southern China, covering early and late Marine Isotope Stage (MIS) 3 and the Holocene, to investigate the spatio-temporal pattern of calcite δ13C changes and the relationship with Asian monsoon (AM) variability. In each growth period, precessional- to millennial-scale changes are clear in the δ18O record. In contrast, millennial variability is absent in the δ13C record, which characterizes persistent centennial oscillations. However, centennial-scale δ18O variations agree well with those of δ13C, with a larger amplitude in δ13C changes (about twice that of δ18O). This suggests that soil humidity balance associated with regional hydrological circulations is important for these centennial δ13C changes, although evaporation-related kinetic fractionation can induce concurrent enrichments in δ18O and δ13C. In frequency, the detrended δ18O and δ13C records are coupled at a periodicity of about 300 yr during the last glacial period and 150 yr during the Holocene. Those centennial-scale δ13C variations are generally consistent with Greenland temperature variability, indicating a climate response over broad regions. Thus, strong co-variation of δ18O and δ13C records should have a climatic origin, even if it is amplified by kinetic effects.

  13. Laser-based, in situ measurements of fine-scale variations in the [delta][sup 18]O values of hydrothermal quartz

    Conrad, M.E.; Chamberlain, C.P. (Dartmouth College, Hanover, NH (United States))

    1992-09-01

    Recently developed laser-based techniques have been used to make in situ measurements of the [delta][sup 18]O values of hydrothermal vein quartz from the Tayoltita and Guanajuato mining districts of Mexico. The [delta][sup 18]O[sub qtz] values within a single 2 [times] 5 cm sample of banded quartz from Guanajuato varied from 12.6[per thousand] to 17.3[per thousand]. Similarly, [delta][sup 18]O[sub qtz] values measured in a 2 [times] 3 cm sample from Tayoltita ranged from 5.7[per thousand] to 9.5[per thousand]. In both cases, the spread of [delta][sup 18]O values measured within individual samples is comparable to the total ranges of [delta][sup 18]O values previously reported for vein samples from the respective districts. Fluid-inclusion homogenization temperatures measured for these samples rule out the possibility that the changes in the [delta][sup 18]O values observed could have been caused by temperature fluctuations; therefore, they must be the result of large shifts in the isotopic composition of the vein fluids.

  14. 13CO and C18O emission from a dense gas disk at z=2.3: abundance variations, cosmic rays and the initial conditions for star formation

    Danielson, A L R; Smail, Ian; Bayet, E; van der Werf, Paul P; Cox, P; Edge, A C; Henkel, C; Ivison, R J

    2013-01-01

    We analyse the SLEDs of 13CO and C18O for the J=1-0 up to J=7-6 transitions in the gravitationally lensed ultraluminous infrared galaxy SMMJ2135-0102 at z=2.3. This is the first detection of 13CO and C18O in a high-redshift star-forming galaxy. These data comprise observations of six transitions taken with PdBI and we combine these with 33GHz JVLA data and our previous 12CO and continuum emission information to better constrain the properties of the ISM within this system. We study both the velocity-integrated and kinematically decomposed properties of the galaxy and coupled with an LVG model we find that the star-forming regions in the system vary in their cold gas properties. We find strong C18O emission both in the velocity-integrated emission and in the two kinematic components at the periphery of the system, where the C18O line flux is equivalent to or higher than the 13CO. We derive an average velocity-integrated flux ratio of 13CO/C18O~1 suggesting a [13CO]/[C18O] abundance ratio at least 7x lower than...

  15. Global isoscapes for δ18O and δ2H in precipitation: improved prediction using regionalized climatic regression models

    Terzer, S.; Wassenaar, L. I.; Araguás-Araguás, L. J.; Aggarwal, P. K.

    2013-11-01

    A regionalized cluster-based water isotope prediction (RCWIP) approach, based on the Global Network of Isotopes in Precipitation (GNIP), was demonstrated for the purposes of predicting point- and large-scale spatio-temporal patterns of the stable isotope composition (δ2H, δ18O) of precipitation around the world. Unlike earlier global domain and fixed regressor models, RCWIP predefined 36 climatic cluster domains and tested all model combinations from an array of climatic and spatial regressor variables to obtain the best predictive approach to each cluster domain, as indicated by root-mean-squared error (RMSE) and variogram analysis. Fuzzy membership fractions were thereafter used as the weights to seamlessly amalgamate results of the optimized climatic zone prediction models into a single predictive mapping product, such as global or regional amount-weighted mean annual, mean monthly, or growing-season δ18O/δ2H in precipitation. Comparative tests revealed the RCWIP approach outperformed classical global-fixed regression-interpolation-based models more than 67% of the time, and clearly improved upon predictive accuracy and precision. All RCWIP isotope mapping products are available as gridded GeoTIFF files from the IAEA website (www.iaea.org/water) and are for use in hydrology, climatology, food authenticity, ecology, and forensics.

  16. Global isoscapes for δ18O and δ2H in precipitation: improved prediction using regionalized climatic regression models

    S. Terzer

    2013-06-01

    Full Text Available A Regionalized Climatic Water Isotope Prediction (RCWIP approach, based on the Global Network for Isotopes in Precipitation (GNIP, was demonstrated for the purposes of predicting point- and large-scale spatiotemporal patterns of the stable isotope compositions of water (δ2H, δ18O in precipitation around the world. Unlike earlier global domain and fixed regressor models, RCWIP pre-defined thirty-six climatic cluster domains, and tested all model combinations from an array of climatic and spatial regressor variables to obtain the best predictive approach to each cluster domain, as indicated by RMSE and variogram analysis. Fuzzy membership fractions were thereafter used as the weights to seamlessly amalgamate results of the optimized climatic zone prediction models into a single predictive mapping product, such as global or regional amount-weighted mean annual, mean monthly or growing-season δ18O/δ2H in precipitation. Comparative tests revealed the RCWIP approach outperformed classical global-fixed regression-interpolation based models more than 67% of the time, and significantly improved upon predictive accuracy and precision. All RCWIP isotope mapping products are available as gridded GeoTIFF files from the IAEA website (www.iaea.org/water and are for use in hydrology, climatology, food authenticity, ecology, and forensics.

  17. Quantitative analysis of cell surface membrane proteins using membrane-impermeable chemical probe coupled with 18O labeling

    Zhang, Haizhen; Brown, Roslyn N.; Qian, Wei-Jun; Monroe, Matthew E.; Purvine, Samuel O.; Moore, Ronald J.; Gritsenko, Marina A.; Shi, Liang; Romine, Margaret F; Fredrickson, James K.; Paša-Tolić, Ljiljana; Smith, Richard D.; Lipton, Mary S.

    2010-01-01

    We report a mass spectrometry-based strategy for quantitative analysis of cell surface membrane proteome changes. The strategy includes enrichment of surface membrane proteins using a membrane-impermeable chemical probe followed by stable isotope 18O labeling and LC-MS analysis. We applied this strategy for enriching membrane proteins expressed by Shewanella oneidensis MR-1, a gram-negative bacterium with known metal-reduction capability via extracellular electron transfer between outer membrane proteins and extracellular electron receptors. LC/MS/MS analysis resulted in the identification of about 400 proteins with 79% of them being predicted to be membrane localized. Quantitative aspects of the membrane enrichment were shown by peptide level 16O and 18O labeling of proteins from wild-type and mutant cells (generated from deletion of a type II secretion protein, GspD) prior to LC-MS analysis. Using a chemical probe labeled pure protein as an internal standard for normalization, the quantitative data revealed reduced abundances in ΔgspD mutant cells of many outer membrane proteins including the outer membrane c-cype cytochromes OmcA and MtrC, in agreement with previously investigation demonstrating that these proteins are substrates of the type II secretion system. PMID:20380418

  18. Dense Cores of Dark Clouds. XII. 13CO and C18O in Lupus, Corona Australis, Vela, and Scorpius

    Vilas-Boas, J. W. S.; Myers, P. C.; Fuller, G. A.

    2000-04-01

    More than 110 dense condensations of the dark clouds in Lupus, Corona Australis, Norma, Vela, and Scorpius were observed in the 13CO and C18O (J=1-0) transitions. The condensations of dark clouds with high star formation activity like the Ophiuchus, Taurus, and Cepheus have average C18O and H2 column densities of 1.8x1015 and 1.1x1022 cm-2. If we take the average size of the condensations to be 0.2 pc, a condensation must have average H2 volumetric densities >=2x104 cm-3 in order to be a good candidate to form stars. The four Lupus filaments have similar radial velocities and velocity dispersions, suggesting that they originated from the same parental cloud. Among these filaments, Lupus 1 is unique in having recent star formation activity, despite the high number of T Tauri stars observed toward the others. Lupus 1 also shows a complex velocity gradient along its main axis. The distribution of radial velocities of the condensations observed toward Scorpius are in good agreement with the hypothesis that they are in a region with expansion velocity smaller than or equal to 18 km s-1. The Corona Australis cloud has velocity gradients ranging from -0.5 km s-1 pc-1 at one extreme to 0.1 km s-1 pc-1 at the other.

  19. Geostatistical Analysis of Spatial Isotope (δ18O, δ2H and 3H) Variability of Groundwater Across Morocco

    Environmental isotopes are increasingly being used for a variety of applications in the fields of the Earth's water cycle and climate change. This paper reports the first national level survey of δ18O, δ2H, 3H and 14C in groundwater across Morocco, including the analysis of the spatial distribution of stable (δ18O and δ2H) and radioactive (tritium and carbon-14) isotopes used to assess eleven groundwater basins distributed across Morocco. The interpolations were carried out using ESRI ArcGIS 9.2 with spatial analyst extension. The methods used are ordinary kriging inverse distance weighting (IDW). The maps showing the spatial variability of tritium and radiocarbon in the basins are used to visualize the presence of modern and old groundwater, while the stable isotope maps show that the age of groundwater, the type (shallow or deep groundwater), the distance of the basin from the sea (Atlantic and Mediterranean) and the altitude are the main factors influencing the isotopic composition of groundwater. Those thematic maps will provide a valuable contribution for sustainable groundwater management of resources for drinking water supplies, agriculture and industry, which is a prime concern in countries dominated by arid and semiarid climates such as Morocco. (author)

  20. Analysis of products of thymine irradiated by 18O8+ ion beam in N2O saturated aqueous solution

    Some methods of capillary gas chromatography, such as GC, GC-MS GC-FT-IR, are used to analyze the products of thymine irradiated by 18O8+ ion beam in N2O saturated aqueous solution. From the results of GC-MS the molecular weight of products can be determined, and from the results of GC-FT-IR some molecular structure information of products can be obtained. By this way the products, 5,6-Dihydro-thymine, 5-Hydroxyl-5-Methylhydantoin, 5-Hydroxyl-6-Hydro-thymine, 5-Hydro-6-Hydroxyl thymine, 5-Hydroxymethyluracil, Trans-Thymine glycol, Cis-Thymine glycol and dimers are determined without separation of them from samples. Though these products are as same as those products of thymine irradiated by γ rays in N2O saturated aqueous solution, the mechanism of thymine irradiated by heavy ion beam in aqueous solution is different from that by γ rays. The main products of thymine irradiated by 18O8+ ion beam in N2O saturated aqueous solution are hydroxyl adducts at 5-6 band of thymine, while the main products of thymine irradiated by γ ray in N2O saturated aqueous solution are dimers of thymine

  1. Protostellar accretion traced with chemistry: Comparing synthetic C18O maps of embedded protostars to real observations

    Frimann, Søren; Padoan, Paolo; Haugbølle, Troels

    2015-01-01

    Context: Understanding how protostars accrete their mass is a central question of star formation. One aspect of this is to try and understand if the time evolution of accretion rates in deeply embedded objects is best characterised by a smooth decline from early to late stages, or by intermittent bursts of high accretion. Aims: We create synthetic observations of deeply embedded protostars in a large numerical simulation of a molecular cloud, which are compared directly to real observations. The goal is to compare episodic accretion events in the simulation to observations, and to test the methodology used for analysing the observations. Methods: Simple freeze-out and sublimation chemistry is added to the simulation, and synthetic C18O line cubes are created for a large number of simulated protostars. The spatial extent of C18O is measured for the simulated protostars, and compared directly to a sample of 16 deeply embedded protostars observed with the Submillimeter Array. If CO is distributed over a larger a...

  2. Isotopic analyses (18O, 13C, 14C) of two meromictic lakes in the Canadian Arctic Archipelago

    Meromictic Lakes Garrow and Sophia in the Canadian Arctic Archipelago were sampled to establish the origin and age of their waters by isotopic studies. The sigma/sub SMOW/18O values reflect the permanent stratification of the waters in both lakes. The mixolimnia contain waters with an isotopic signal between -13.16 and -2.198%, coherent with the values of precipitation in these high latitudes. The short residence time of the water in this layer makes it possible to record episodic variations of the freshwater inputs to the lakes. In the chemoclines, the sigma18O values increase to -10% concomitantly with a rise in chloride content to 42 g liter-1. This corresponds to a conservative mixing of surficial and deep waters. In the monimolimnia, hypersaline waters from brine production during permafrost growth in the watershed, according to a Rayleigh process. The brines drained toward the deepest part of each lake, after postglacial uplift, and became isolated. 14C dating of total inorganic carbon in the Lake Garrow monimolimnion gave an age of 2580 +/- 260 years B.P. In Lake Sophia, the deep waters exhibit recent 14C activity (121.4% modern carbon) that suggests recent infiltration of seawater into the lake basin

  3. CRDS detection and modelling of vibrational bands of 18O3 approaching the dissociation threshold (7400–7920 cm−1)

    The absorption spectrum of the 18O3 isotopologue of ozone is recorded by CW-Cavity Ring Down Spectroscopy between 7400 and 7920 cm−1. The typical noise equivalent absorption of the recordings is αmin≈1×10−10 cm−1 allowing for the detection of extremely weak vibrational bands located only a few % below the dissociation limit. The absorption spectrum also includes the weak 3A2(000)–X(110) hot vibronic band at 7877.53 cm−1 affected by predissociation broadening. Overall, about 1000 lines were rovibrationnally assigned to six vibrational bands. Their line positions were modelled using effective Hamiltonian models covering three vibrational interacting systems and involving several “dark” states perturbing observed transitions. Line positions could be reproduced with rms deviations on the order of 0.01 cm−1. The dipole transition moment parameters of the six bands were determined from the retrieved line intensities. The obtained set of effective parameters and the experimentally determined energy levels were used to generate a list of 1461 transitions provided as Supplementary materials. - Highlights: • Cavity Ring Down Spectroscopy of 18O3 between 7400 and 7920 cm−1. • 1017 Transitions assigned to six A-type vibrational bands. • Upper vibrational states located a few % below the dissociation limit at 8560 cm−1. • Effective operator modelling of the spectra. • Good agreement with ab initio values for the band centres and rotational constants

  4. Study of some excited states in 21Ne-21Na, 18O-18F and 15N-15O nuclei

    The study of 21Ne-21Na, 18O-18F and 15N-15O nuclei was performed through proton capture and transfer reactions and allows to determine the spins and parities of some excited states, give the gamma deexcitation schemes of these levels, compute the neutron and proton reduced width γ2sub(n) and γ2sub(p). The levels studied are: in 21Na 4.1520Ne(p,p), (p,p'), (p,p'γ) and (pγ) reactions) and in 21Ne: E(exc)=4.73, 5.69 and 5.78 MeV (20Ne (p,p) reaction); in 18O: E(exc)17O(d,p) reaction); in 15O: 8.92 MeV doublet and 8.98 MeV level (angular correlation 14N(p,γγ) and in 15N: 9.0514N(d,p) reaction). A comparison with theoretical results is discussed and analog states are pointed out

  5. High resolution analysis of 32S18O2 spectra: The ν1 and ν3 interacting bands

    Ulenikov, O. N.; Bekhtereva, E. S.; Krivchikova, Yu. V.; Morzhikova, Yu. B.; Buttersack, T.; Sydow, C.; Bauerecker, S.

    2015-11-01

    Highly accurate, ~(1 - 2) ×10-4cm-1, ro-vibrational spectrum of S18O2 was recorded with Bruker IFS 120 HR Fourier transform interferometer in the region of 1050-1400 cm-1 where the bands ν1 and ν3 are located. About 1560 and 1840 transitions were assigned in the experimental spectrum with the maximum values of quantum numbers Jmax. /Kamax. equal to 65/22 and 58/16 to the bands ν3 and ν1, respectively. The further weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account Coriolis resonance interaction between the vibrational states (100) and (001). To make the ro-vibrational analysis physically more suitable, the initial values of main spectroscopic parameters have been estimated from the values of corresponding parameters of the S16O2 species on the basis of the results of the Isotopic Substitution theory. Finally, the set of 23 spectroscopic parameters obtained from the fit reproduces values of 1292 initial "experimental" ro-vibrational energy levels (about 3400 transitions assigned in the experimental spectrum) with the drms = 0.00015cm-1. Also, the ground state parameters of the S18O2 molecule were improved.

  6. Variability of 10Be and δ18O in snow pits from Greenland and a surface traverse from Antarctica

    To examine temporal variability of 10Be in glacial ice, we sampled snow to a depth of 160 cm at the NEEM (North Greenland Eemian Ice Drilling) drilling site in Greenland. The samples span three years between the summers of 2006 and 2009. At the same time, spatial variability of 10Be in glacial ice was explored through collection of the upper ∼5 cm of surface snow in Antarctica during part of the Swedish–Japanese traverse from Svea to Syowa station during the austral summer in 2007–2008. The results of the Greenlandic 10Be snow suggested variable concentrations that apparently do not clearly reflect the seasonal change as indicated by the δ18O data. The 10Be concentration variability most likely reflects also effects of aerosol loading and deposition pathways, possibly in combination with post-depositional processes. The Antarctic traverse data expose a negative correlation between 10Be and δ18O, while there are weaker but still significant correlations to altitude and distance to the coast (approximated by the distance to the 70th latitude). These relationships indicate that geographical factors, mainly the proximity to the coast, may strongly affect 10Be concentrations in snow in Queen Maud Land, Antarctica.

  7. Quantitative Proteomic Analysis of Mouse Embryonic Fibroblasts and Induced Pluripotent Stem Cells Using 16O /18O labeling

    Huang, Xin; Tian, Changhai; Liu, Miao; Wang, Yongxiang; Tolmachev, Aleksey V.; Sharma, Seema; Yu, Fang; Fu, Kai; Zheng, Jialin; Ding, Shi-Jian

    2012-04-06

    Induced pluripotent stem cells (iPSC) hold great promise for regenerative medicine as well as for investigations into the pathogenesis and treatment of various diseases. Understanding of key intracellular signaling pathways and protein targets that control development of iPSC from somatic cells is essential for designing new approaches to improve reprogramming efficiency. Here we report the development and application of an integrated quantitative proteomics platform for investigating differences in protein expressions between mouse embryonic fibroblasts (MEF) and MEF-derived iPSC. This platform consists of 16O/18O labeling, multidimensional peptide separation coupled with tandem mass spectrometry, and data analysis with UNiquant software. Using this platform a total of 2,481 proteins were identified and quantified from the 16O/18O-labeled MEF-iPSC proteome mixtures with a false discovery rate of 0.01. Among them, 218 proteins were significantly upregulated, while 247 proteins were significantly downregulated in iPSC compared to MEF. Many nuclear proteins, including Hdac1, Dnmt1, Pcna, Ccnd1, Smarcc1, and subunits in DNA replication and RNA polymerase II complex were found to be enhanced in iPSC. Protein network analysis revealed that Pcna functions as a hub orchestrating complicated mechanisms including DNA replication, epigenetic inheritance (Dnmt1) and chromatin remodeling (Smarcc1) to reprogram MEF and maintain stemness of iPSC.

  8. Multiple tree-ring chronologies (ring width, δ13C and δ18O) reveal dry and rainy season signals in Indonesia

    Schollaen, Karina; Heinrich, Ingo; Neuwirth, Burkhard; Krusic, Paul; D`Arrigo, Rosanne; Karyanto, Oka; Helle, Gerhard

    2013-04-01

    The tropical Indonesian region plays a key role in the global climate system because of the enormous heat and moisture exchange between ocean and atmosphere in that area. Here, we evaluate the influence of rainfall variability on multiple tree-ring parameters of Teak (Tectona grandis) trees growing in a lowland rain forest in Central Java (Indonesia). Three, annually resolved, chronologies of tree-ring width, stable carbon (δ13C) and oxygen (δ18O) isotopes were developed for the twentieth century (1900-2007). Climate response analysis with regional rainfall data has revealed that all three tree-ring parameters are significantly sensitive to rainfall during different intervals of the seasonal monsoon pattern. The amount of rainfall at the beginning of the rainy season (Sep-Nov) is important for tree-ring width, confirming previous studies. The stable isotope records best represent slightly different sub-periods of the prime rainy season (δ13C: Dec-May; δ18O: Nov-Feb) with negative correlations. Tree-ring δ18O additionally responds well to peak dry season rainfall with positive correlation. The correlations of opposite sign reflect the distinct seasonal contrast of the δ18O signatures of rainfall during the dry (18O-enriched rain) and rainy (18O-depleted rain) seasons in conjunction with changing rainfall amount. Dry season periods with rainfall amounts above average have an exceptionally strong influence on tree-ring δ18O in years with below average rainy season rainfall. In such cases, the dry season signal reduces the signal strength of the prime rainy season in tree-ring δ18O. However, the rainy season signal is still strong and stable over the 20th century. Further, the δ18O record correlates with several ENSO events, supported by spectral analysis which reveals significant peaks on the 2-4 year band. Highly resolved intra-annual δ18O isotope analyses suggest that the signals of dry and rainy season can be distinguished clearly and demonstrate a new

  9. Contributions of evaporation, isotopic non-steady state transpiration and atmospheric mixing on the delta18O of water vapour in Pacific Northwest coniferous forests.

    Lai, Chun-Ta; Ehleringer, James R; Bond, Barbara J; Paw U, Kyaw Tha

    2006-01-01

    Changes in the 2H and 18O of atmospheric water vapour provide information for integrating aspects of gas exchange within forest canopies. In this study, we show that diurnal fluctuations in the oxygen isotope ratio (delta 18O) as high as 4% per hundred were observed for water vapour (delta (18)Ovp) above and within an old-growth coniferous forest in the Pacific Northwest region of the United States. Values of delta 18Ovp decreased in the morning, reached a minimum at midday, and recovered to early-morning values in the late afternoon, creating a nearly symmetrical diurnal pattern for two consecutive summer days. A mass balance budget was derived and assessed for the 18O of canopy water vapour over a 2-d period by considering the 18O-isoflux of canopy transpiration, soil evaporation and the air entering the canopy column. The budget was used to address two questions: (1) do delta 18O values of canopy water vapour reflect the biospheric influence, or are such signals swamped by atmospheric mixing? and (2) what mechanisms drive temporal variations of delta 18Ovp? Model calculations show that the entry of air into the canopy column resulted in an isotopically depleted 18O-isoflux in the morning of day 1, causing values of delta 18Ovp, to decrease. An isotopically enriched 18O-isoflux resulting from transpiration then offset this decreased delta 18Ovp later during the day. Contributions of 18O-isoflux from soil evaporation were relatively small on day 1 but were more significant on day 2, despite the small H2(16)O fluxes. From measurements of leaf water volume and sapflux, we determined the turnover time of leaf water in the needles of Douglas-fir trees as approximately 11 h at midday. Such an extended turnover time suggests that transpiration may not have occurred at the commonly assumed isotopic steady state. We tested a non-steady state model for predicting delta 18O of leaf water. Our model calculations show that assuming isotopic steady state increased isoflux of

  10. {sup 18}O, {sup 2}H and {sup 3}H isotopic composition of precipitation and shallow groundwater in Olkiluoto

    Hendriksson, N. [Geological Survey of Finland, Espoo (Finland); Karhu, J.; Niinikoski, P. [Univ. of Helsinki (Finland)

    2014-12-15

    The isotopic composition of oxygen and hydrogen in local precipitation is a key parameter in the modelling of local water circulation. This study was initiated in order to provide systematic monthly records of the isotope content of atmospheric precipitation in the Olkiluoto area and to establish the relation between local rainfall and newly formed groundwater. During January 2005 - December 2012, a total of 85 cumulative monthly rainfall samples and 68 shallow groundwater samples were collected and the isotopic composition of oxygen and hydrogen was recorded for all those samples. Tritium values are available for 79 precipitation and 65 groundwater samples. Based on the 8-year monitoring, the long-term weighted annual mean isotope values of precipitation and the mean values of shallow groundwater are -11.59 per mille and -11.27 per mille for δ{sup 18}O, - 82.3 per mille and -80.3 per mille for δ{sup 2}H and 9.8 and 9.1 TU for tritium, respectively. Based on these data, the mean stable isotope ratios of groundwater represent the long-term mean annual isotopic composition of local precipitation. The precipitation data were used to establish the local meteoric water line (LMWL) for the Olkiluoto area. The line is formulated as: δ{sup 2}H = 7.45 star δ{sup 18}O + 3.82. The isotope time series reveal a change in time. The increasing trend for the δ{sup 18}O and δ{sup 2}H values may be related to climatic variability while the gradual decline observed in the {sup 3}H data is attributed to the still continuing decrease in atmospheric {sup 3}H activity in the northern hemisphere. The systematic seasonal and long-term tritium trends suggest that any potential ground-level tritium release from the Olkiluoto nuclear power plants is insignificant. The d-excess values of Olkiluoto precipitation during the summer period indicated that a notable amount of re-cycled Baltic Sea water may have contributed to precipitation in the Finnish southern coast. Preliminary estimates

  11. How the Pyrenees influence the δ18O and δD compositions of rain and rivers?

    Huyghe, Damien; Mouthereau, Frederic; Sebilo, Mathieu; Segalen, Loic

    2016-04-01

    Documenting Earth surface past elevation is critical to understand the dynamics of collisional domains and to investigate tectonics vs. climate interactions and their relative influence on erosion and sedimentation. Topography exerts a direct control on precipitation and it is possible to determine the paleoelevation of a mountain range from analyses of minerals created from paleorainfall, because the isotopic composition of rain (δ18O & δD) decreases with elevation. Topography modifies the patterns of atmospheric circulation and thus the local isotopic lapse rate and the resulting isotope-in-precipitation patterns at high elevation. Thus, before reconstructing paleoelevation, the local modern isotope lapse rate has to be documented to quantify the amount of orographic effect on precipitation and get a first-order understanding of the interactions of topography and rainfall in the study area. Here, we characterize the modern isotope lapse rate in the Pyrenees, a well-know collisional orogen, which is a privileged area for paleotopographic investigations. It presents the advantage to be a small orogen, with mean maximum elevation of ~3000 m, which allows for a reliable and large sampling. We sampled streams and creeks from small catchments that integrate near-surface runoff (i.e., precipitation) over months to years and hence provide a time-averaged signal of elevation. We collected 100 samples in 9 different valleys from N and S Pyrenees during the dry season (August and July), because it is the period during which groundwater, which is comprised by a mixture of rainfall of the annual cycle, dominates the stream water budget. Results reveal a good correlation of δ18O vs. δD values and mean δ18O and δD altitudinal gradients of -3.6‰ and -29‰ /km respectively. Distinct areas can be distinguished over the range according to their isotopic features. In particular, the southern Pyrenees exhibit lowers ratios than the north, suggesting an orographic effect of

  12. Determination of the δ15N and δ18O of nitrate in water; RSIL lab code 2900

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2900 is to determine the δ15N and δ18O of nitrate (NO3-) in water. The δ15N and δ18O of the dissolved NO3- are analyzed by converting the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of the NO3- to N2O, which follows the pathway shown in equation 1: NO3- → NO2- → NO → 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before δ15N values are reported.

  13. Determination of the δ15N and δ18O of nitrate in solids; RSIL lab code 2897

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2897 is to determine the δ15N and δ18O of nitrate (NO3-) in solids. The NO3- fraction of the nitrogen species is dissolved by water (called leaching) and can be analyzed by the bacterial method covered in RSIL lab code 2900. After leaching, the δ15N and δ18O of the dissolved NO3- is analyzed by conversion of the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of NO3- to N2O, which follows the pathway shown in equation 1: NO3- → NO2- → NO → 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before δ15N values are reported.

  14. Formation of low-δ18O magmas of the Kangerlussuaq Intrusion by addition of water derived from dehydration of foundered basaltic roof rocks

    Riishuus, Morten S.; Harris, Chris; Peate, David W.; Tegner, Christian; Wilson, J. Richard; Brooks, C. Kent

    2015-05-01

    The Kangerlussuaq Intrusion in East Greenland is concentrically zoned from quartz nordmarkite (quartz syenite) at the margin, through pulaskite, to foyaite (nepheline syenite) in the centre, with no apparent intrusive contacts. The δ18O values of coexisting minerals are consistent with oxygen isotope equilibrium at magmatic temperatures. Most of the intrusion formed from low-δ18O magma; magma δ18O values generally increased upwards from about 3.3 ‰ in the quartz nordmarkites to 5.6 ‰ in the foyaites. The lowest magma δ18O value of about -1.0 ‰ is from the upper part of the nordmarkites, where there is a high concentration of foundered basaltic xenoliths (stoped from the roof of the intrusion). The amphiboles in the syenites have δD values that range from those typical of hydrous mantle-derived minerals to much lower values (-86 to -157 ‰), as do whole-rock samples of xenolith and country rock (-125 to -148 ‰). The low magma δ18O and δD values are consistent with continuous incorporation, exchange and upward escape of low-δ18O and δD fluids released from stoped basaltic roof material. Mass balance suggests that the integrated amount of water involved was 7 wt% of the volume of the magma, but locally reached 30 wt% water. The requirement for large amounts of water with low δ18O value is satisfied only if the foundered basalt contained most of its water in cavities as opposed to hydrous minerals. Even with this requirement, the volume of stoped basalt would have been equal to the volume of the magma. Repeated recharge of the residual magma with progressively less contaminated silica undersaturated melt resulted in a gradual shift across the low-pressure thermal divide. Crystallisation was suppressed by the depression of the liquidus due to water saturation of the residual magma (pH2O ~1 kbar).

  15. Simultaneous Measurement of δ2H, δ17O, and δ18O in H2O using a Commercial Cavity Ringdown Spectrometer

    Dominguez, G.; Salvo, C.; Gormally, J.

    2012-12-01

    Quantifying the abundance of oxygen and hydrogen isotopes found in H2O from natural systems and laboratory experiments can be used to better understand physical-chemical processes. While much attention has traditionally been paid to 18O/16O and D/H ratios in natural samples, advances in the precision of mass-spectrometric techniques have exploited small differences in the relative changes of 18O/16O and 17O/16O ratios that are induced by different photochemical and chemical processes such as diffusion and evaporation. In recent years, commercial instruments employing infrared spectroscopy have been shown to be capable of resolving 18O/16O ratios in H2O samples with precisions that are comparable to traditional IRMS techniques. Here we show that, with a modest amount of work, a widely distributed commercial water vapor spectroscopic instrument designed for the determination of {{18}O/{16}^O} and D/H ratios in samples (Picarro L2120-i) can be used to also be used to simultaneously determine the 17O/16O ratio of water samples. Using this instrument, we performed simple evaporation experiments to determine the effect of H2O evaporation (T=40-70C) on the relative ratios of 17O/16O and 18O/16O of residual water. Our results agree with Angert et al. (2004) theoretical prediction for this fractionation. In addition, our results confirm that relative changes in 18O/16O vs. D/H for evaporative conditions follow a slope that is significantly less than 8 (δ 18O vs. D/H) , the value expected for equilibrium conditions. This technique should prove helpful for acquiring data on the multi-isotopic fractionation induced by physical-chemical processes such as evaporation and diffusion in field and laboratory investigations.

  16. Intercomparison of 20th century tropical climate model hindcasts and coral δ18O data using a forward proxy system model

    Thompson, D. M.; Ault, T. R.; Evans, M. N.; Cole, J. E.; Emile-Geay, J.

    2010-12-01

    When coupled to climate model (CGCM) output, forward models provide a means to assess CGCM output through direct comparison with the available proxy observations. Here we model reef coral oxygen isotopic composition (δ18O) as a function of sea-surface temperature (SST) and sea-surface salinity (SSS), with SSS acting as a linear proxy for the isotopic composition of seawater. When driven with historical SST and SSS data over the 1958-1990 period, the forward model is able to capture the spatial pattern and temporal evolution of the El Niño-Southern Oscillation (ENSO) and trend observed in a sparse observational network of 23 Indo-Pacific coral δ18O records. The SST and SSS components of the model are both necessary to capture the full magnitude of the coral trend. The δ18O trend simulated from historical SST and SSS data is equivalent to or smaller than the observed δ18O trend. For the 1890-1990 period, δ18O records simulated from AR4 CGCMs generally display greater overall interannual variance and a weaker 20th century warming/freshening trend than is observed in corals. The discrepancies between observed and CGCM-simulated δ18O trends may arise in part from unmodeled physiological controls on δ18O or from sampling-network induced biases. On the other hand, the tropical Pacific may be more sensitive to radiative changes during the 20th century than is simulated by the AR4 generation of CGCMs.

  17. WO3 nano-spheres into W18O49 one-dimensional nano-structures through thermal annealing.

    Mwakikunga, B W; Sideras-Haddad, E; Arendse, C; Witcomb, M J; Forbes, A

    2009-05-01

    We elaborate the size controlled synthesis of nano-spheres and nano-crystals of WO3 by ultrasonic spray pyrolysis. The as-deposited particles are predominantly spherical in shape and tend to exhibit less agglomeration and a decrease in diameter as the process temperature is increased. Characterization was carried out using transmission (TEM) and scanning (SEM) electron microscopy, energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). One-dimensional nano-structures with the highest yield of WOx nano-wires were observed in a sample synthesized at 500 degrees C but only after thermal annealing of this sample at 500 degrees C for 17 hour in flowing argon. XRD revealed a high deficiency in oxygen in all samples suggesting that the nano-structures are transformed to sub-oxides of tungsten. Micro-diffraction patterns of a typical nano-wire reveal the monoclinic phase of W18O49. PMID:19453005

  18. Ontogeny and habitat change in Mesozoic cephalopods revealed by stable isotopes ( δ18O, δ13C)

    Lukeneder, Alexander; Harzhauser, Mathias; Müllegger, Stefan; Piller, Werner E.

    2010-07-01

    Stable isotope ( δ18O and δ13C) ratios were measured in successive aragonitic shell sequences of ammonoids (class Cephalopoda) to determine whether their depth distributions changed within ontogeny and whether stable isotope values differ in various morphological groups (e.g. Leiostraca vs. Trachyostraca). We concentrate mainly on δ18O for temperature results and added δ13C data to obtain information on the ontogenetic history, for which full spiral measurements were undertaken for the first time. To obtain valid stable isotope data from ammonoid shells, we measured ontogenetic sequences (full shell) within different genera. Data sets from the Jurassic ( Cadoceras) and Cretaceous ( Hypacanthoplites, Nowakites) were chosen due to the pure primary aragonitic shell preservation. The study was designed to extract better information on the habitat and life cycle of fossil cephalopods (e.g. ammonoids) in comparison with recent cephalopods (e.g. Nautilus, Spirula, Sepia) possessing equivalent or comparable hard parts. The data from three genera suggest different modes of life in at least two morphological groups. We detected and established two main groups with different ontogenetic strategies based on the δ18O data. The wcw-type (warm-cool-warm type) of Cadoceras resembles strategies in Nautilus and Sepia, which migrate from shallow into deeper environments and back in ontogeny ( wc-type, warm-cool-type), and the cw-type (cool-warm type) of Hypacanthoplites resembling the first two migration phases of Spirula ( cwc-type), which migrates from deeper into shallower and back again into deeper habitats. The main (three) phases revealed by both δ18O and δ13C data sets most probably reflect diet changes in juvenile to mid-aged individuals, followed by a habitat change for spawning adults. In Cadoceras the temperatures range from 21.2 °C for juveniles down to 12.1 °C for mid-aged individuals and back up 16.9 °C in adults. The cw- type strategy of Hypacanthoplites

  19. Study of 2H and 18O in the Kouris catchment (Cyprus) for the description of the regional groundwater balance

    The Kouris catchment covers 300 km2 on the southern side of the Troodos Massif of Cyprus and bounded on the South by the Mediterranean Sea. Elevations range from 2000 m to sea level within a distance of 30 km. The basin consists of an ophiolitic complex in the North (ultramafic rocks, gabbros, sheeted dykes and pillow lavas) and an overlying sedimentary complex in the South (chalks, marls, calcarenites and limestones). The ophiolites highly heterogeneous and contain the major groundwater resources in Cyprus. While the geology of the Troodos Massif is very well documented, the hydrogeology of the area is much less known. The aim of this study is to apply 144 new and 72 published analysis of δD and δ18 in groundwater as well as as new and reported in IAEA database analysis of rainfall samples for better understanding of main mechanisms of ground water flow and for checking the assumptions of the groundwater model, developed at the previous stage. 2H and 18O in Precipitation. 2H and 18O contents in rainfall over the Kouris catchment samples are linearly related by the equation of the local meteoric water line: δD = 6.5*δ18 + 10.6 that differs from the equation of the Global Meteoric Water Line by a smaller slope, indicating partial evaporation of rain drops prior to infiltration. Seasonal variations might be extremely high (-36 per mille for δD and -5.5 per mille for δ18 in 2000/2001). Averaged monthly mixed rainfall samples for October-February 2000/2001 at the two meteostations and some data from springs at the highest altitudes suggest the regression equation for δD(per mille) and the altitude(m): δD = -0.012H(m) - 24,86 (1), where H(m) - the altitude of the rainfall 2H and 18O in groundwater. Almost all points at the 2H versus 18O diagram (except some in the ophiolites) are displaced from the local meteoric water line due to evaporation. Samples taken from the sedimentary rocks seem to be more affected by evaporation than those in ophiolites. Seasonal

  20. Structural and Electronic Properties of Polyoxovanadoborates Containing the [V12B18O60] Core in Different Mixed Valence States

    Patricio Hermosilla-Ibáñez

    2015-07-01

    Full Text Available This review summarizes all published data until April 2015 related to crystalline lattices formed by the [V12B18O60] core, which generates polyanionic clusters with different degrees of protonation and mixed-valence ratios. The negative charge of this cluster is counterbalanced by different cations such as protonated amines, hydronium, and alkaline, and transition metal ions. The cluster is shown to form extended 1D, 2D, or 3D frameworks by forming covalent bonds or presenting hydrogen bond interactions with the present secondary cations. These cations have little influence on the solid state reflectance UV-visible spectra of the polyanionic cluster, but are shown to modify the FT-IR spectra and the magnetic behavior of the different reported species.

  1. Developed Method for Nitrate Extraction and Purification to Measure d18O-NO3- Composition in Water

    A procedure suitable for measuring d18O-NO3- in waters with moderate ionic strengths and high DOC loads has been established. The conditions necessary to effect complete nitrate recovery and complete removal of other oxygen containing anions and DOC without scarifying the isotopic signature of nitrate were investigated. The wet chemistry train developed for extraction and purification of nitrate from the liquid matrix consists of the following consecutive steps: sulfate precipitation using barium hydroxide, filtration, cation exchange, anion exchange, elution, neutralization and adsorption. A mixed neutralization scheme comprising neutralization using silver oxide and potassium hydroxide has been devised and implemented. Many DOCs removal pathways have been evaluated with regard to their DOCs removal efficiency and negative effects on sample -nitrate pool as well as the oxygen isotope composition of nitrate. Preservation experiments revealed that addition of 1/4 ml chloroform (99.8%) per one liter sample is an effective way of preserving nitrate pool

  2. Effects of stem cell therapy on protein profile of parkinsonian rats using an(18) O-labeling quantitative proteomic approach.

    Liu, Yahui; Liu, Kefu; Qin, Wei; Liu, Chenghao; Zheng, Xiaowei; Deng, Yulin; Qing, Hong

    2016-03-01

    The application of neural stem cell (NSC) research to neurodegenerative diseases has led to promising clinical trials. Currently, NSC therapy is most promising for Parkinson's disease (PD). We conducted behavioral tests and immunoassays for the profiling of a PD model in rats to assess the therapeutic effects of NSC treatments. Further, using a multiple sample comparison workflow, combined with (18) O-labeled proteome mixtures, we compared the differentially expressed proteins from control, PD, and NSC-treated PD rats. The results were analyzed bioinformatically and verified by Western blot. Based on our initial findings, we believe that the proteomic approach is a valuable tool in evaluating the therapeutic effects of NSC transplantation on neurodegenerative disorders. PMID:26791447

  3. 22 years cycle in the planktonic {delta}{sup 18} O of a shallow-water Ionian sea area

    Cini Castagnoli, G.; Bonino, G.; Taricco, C. [Turin Univ., Turin (Italy). Dipt. di Fisica Generale; Consiglio Nazionale delle Ricerche, Turin (Italy). Ist. di Cosmogeofisica

    2000-08-01

    The {delta}{sup 18} O profile of Globigerinoides ruber was measured in the GT90/3 Ionian sea core between 1205 and 1898 AD. The high temporal resolution of 3.87 years allowed to determine the presence in the time series of an 11 years component with an amplitude of 0.07%, at significance level of 99% (by Monte Carlo singular spectrum analysis, MC-SSA). The paper focuses attention on 22 years periodicity in the time series and shows the Hale solar cycle, obtained by inverting the odd cycles of the sunspot number series. This result shows that the even and odd Schwabe cycles do not have the same influence on this climatic record.

  4. An assessment of the isotopic (2H/18O) integrity of water samples collected and stored by unattended precipitation totalizers

    Terzer, Stefan; Wassenaar, Leonard I.; Douence, Cedric; Araguas-Araguas, Luis

    2016-04-01

    The IAEA-WMO Global Network of Isotopes in Precipitation (GNIP) provides worldwide δ18O and δ2H data for numerous hydrological and climatological studies. The traditional GNIP sample collection method relies on weather station operators to accumulate precipitation obtained from manual rain gauges. Over the past decades, widespread weather station automatization resulted in the increased use of unattended precipitation totalizers that accumulate and store the rainwater in the field for up to one month. Several low-tech measures were adopted to prevent in situ secondary evaporative isotopic enrichment (SEE) of totalized water samples (i.e. disequilibrium isotopic fractionation after precipitation is stored in the collection device). These include: (a) adding a 0.5-1 cm floating layer of paraffin oil to the totalizer bottle, (b) using an intake tube leading from the collection funnel and submerged to the bottom of the totalizer bottle, or (c) placing a table tennis ball in the funnel aiming to reduce evaporation of the collected water from the receiving bottle to the atmosphere. We assessed the isotopic integrity of stored rainwater samples for three totalizers under controlled settings: each aforementioned totalizer was filled with a 100 or 500 mL of isotopically known water and installed in the field with the intake funnels sheltered to prevent rainwater collection. Potential evapotranspiration (PET) was obtained from on-site meteorological recordings. Stored evaporative loss from each totalizer was evaluated on a monthly basis; gravimetrically and by analysing δ18O and δ2H of the stored water, for a period of 6 months and a cumulative PET of ˜500 mm. The gravimetric and isotope results revealed that for smaller water volumes (100 ml, corresponding to ca. 5 mm of monthly precipitation), negligible isotope enrichment (δ18O) was observed in the paraffin-oil based totalizer, whereas unacceptable evaporative isotope effects were observed for the ball

  5. Extraction of Water from Soil and Plant Samples for 18O/16O and D/H Isotope Ratio Measurements

    The need for a rapid, inexpensive technique for routine extraction of water from plant and soil samples for Oxygen-18/Oxygen-16 (18O/16O) and Hydrogen-2/Hydrogen-1 (D/H) isotope ratio measurements is increasing due to the greater demand for isotopic data in agroecological, soil water, evaporation and transpiration partitioning and hydrological studies. The common sample extraction technique is vacuum distillation. Most of the current techniques are laborious, time consuming and involve complicated setups with specially-made glass apparatus. In addition, liquid nitrogen or dry ice is needed to freeze and trap water vapour evaporated during extraction. Both of these cooling agents can be difficult to acquire in many developing countries. With water isotope analyses becoming cheaper, easier and faster (e.g. through the development of modern laser isotope analysers), the bottleneck in sample throughput is often the water extraction time from the soil and plant samples instead of the isotopic analysis of water

  6. Deuterium and 18O as indicators of evaporation losses from rice crops in semi-arid climate zones

    Rice requires the highest water application rate of any of the major grain crops, with total water demand per unit area of crop at least twice that of maize or wheat. Most of the water used for rice production in semi-arid climates is lost to the atmosphere through the combined effects of evaporation and transpiration. Evaporation leads to substantial enrichment of residual liquid phase water molecules containing heavier isotopes (deuterium and 18O) because of preferential loss to the atmosphere of lighter isotope molecules. In contrast, transpiration leads to little net enrichment of the heavier isotopes in residual waters. This difference between the effects on the stable isotopic composition of surface water of the two loss modes to the atmosphere offers the potential to estimate arid zone evaporation losses independent of transpiration, both in natural waters, such as swamps, and in regional scale irrigation networks. 3 refs, 2 figs

  7. The influence of temperature and seawater carbonate saturation state on 13C–18O bond ordering in bivalve mollusks

    R. A. Eagle

    2013-07-01

    Full Text Available The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ18O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of 13C–18O bond abundance, denoted by the measured parameter Δ47, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a range in water temperatures of 5 to 25 °C, and field collected specimens spanning a range of −1 to 29 °C. In addition we investigate the potential influence of carbonate saturation state on bivalve stable isotope compositions by making measurements on both calcitic and aragonitic specimens that have been cultured in seawater that is either supersaturated or undersaturated with respect to aragonite. We find a robust relationship between Δ47 and growth temperature. We also find that the slope of a linear regression through all the Δ47 data for bivalves plotted against seawater temperature is significantly shallower than previously published inorganic and biogenic carbonate calibration studies produced in our laboratory and go on to discuss the possible sources of this difference. We find that changing seawater saturation state does not have significant effect on the Δ47 of bivalve shell carbonate in two taxa that we examined, and we do not observe significant differences between Δ47-temperature relationships between calcitic and aragonitic taxa.

  8. CHIMPS: the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey

    Rigby, A. J.; Moore, T. J. T.; Plume, R.; Eden, D. J.; Urquhart, J. S.; Thompson, M. A.; Mottram, J. C.; Brunt, C. M.; Butner, H. M.; Dempsey, J. T.; Gibson, S. J.; Hatchell, J.; Jenness, T.; Kuno, N.; Longmore, S. N.; Morgan, L. K.; Polychroni, D.; Thomas, H.; White, G. J.; Zhu, M.

    2016-03-01

    We present the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) which has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The high-resolution spectral survey currently covers |b| ≤ 0.5° and 28° ≲ l ≲ 46°, with an angular resolution of 15 arcsec in 0.5 km s-1 velocity channels. The spectra have a median rms of ˜0.6 K at this resolution, and for optically thin gas at an excitation temperature of 10 K, this sensitivity corresponds to column densities of NH2 ˜ 3 × 1020 cm-2 and NH2 ˜ 4 × 1021 cm-2 for 13CO and C18O, respectively. The molecular gas that CHIMPS traces is at higher column densities and is also more optically thin than in other publicly available CO surveys due to its rarer isotopologues, and thus more representative of the three-dimensional structure of the clouds. The critical density of the J = 3 → 2 transition of CO is ≳104 cm-3 at temperatures of ≤20 K, and so the higher density gas associated with star formation is well traced. These data complement other existing Galactic plane surveys, especially the JCMT Galactic Plane Survey which has similar spatial resolution and column density sensitivity, and the Herschel infrared Galactic Plane Survey. In this paper, we discuss the observations, data reduction and characteristics of the survey, presenting integrated-emission maps for the region covered. Position-velocity diagrams allow comparison with Galactic structure models of the Milky Way, and while we find good agreement with a particular four-arm model, there are some significant deviations.

  9. Investigation on the interactions between soil water, irrigation and transpiration in the soil-plant-atmosphere continuum with 18O

    Full text: The complex interaction between plant and soil water during the cropping season requires further investigation. How does the plant react in terms of transpiration to water stress during its growth? How is the interaction between the plant, the soil water and irrigation at different levels of water stress? These are the questions to be answered by a pot experiment conducted in a glasshouse at Seibersdorf laboratories involving 18O. Oxygen 18 is a rare (natural abundance of 0.2 %), natural and stable isotope of water and therefore very useful for tracking water pathways from irrigation or precipitation within the soil-plant-atmosphere continuum. One of the noteworthy properties of 18O is the temperature dependency of its fractionation factor between the liquid phase and the vapour during evaporation, while the plant water uptake does not change the isotopic signature of soil water. These two properties can be exploited to investigate not only soil evaporation and plant transpiration but also the irrigation water pathway within the soil-plant-atmosphere continuum. Thirty six large pots (diam. 50 cm) were filled with a 1:1 Seibersdorf soil (diam. 0.5 cm)/quartz sand mixture in a randomised block experiment, consisting of 3 treatments: (i) field capacity + crop, (ii) 60% of field capacity + crop and (iii) 60% of field capacity + bare soil. The crop used for the experiment is corn (Zea Mays). Climatic data and soil humidity will be monitored during the cropping season. Oxygen 18 in irrigation, soil and plant water (sap and dry organic matter) at different stages of plant growth will be analysed. Soil water and plant sap will need to be extracted before isotopic analyses with the mass-spectrometer can be conducted, involving the construction of a cryodistillation line in the laboratory. (author)

  10. IAEA inter-laboratory comparison exercise for δ2H and δ18O analysis of water samples

    Isotope Hydrology laboratories routinely use oxygen and hydrogen isotope ratios in water samples to delineate water sources and processes involved in the hydrological cycles, for palaeo-climatic research and other applications. For this purpose it is of importance to maintain stringent precision and accuracy in the isotope ratio analyses since signals of natural variations are not large and conclusions often depend on how accurately one can measure these small signals. In this context, the IAEA Isotope Hydrology Laboratory organised a Inter-laboratory Comparison Exercise for δ2H and δ18O of water samples (WICO2002) recently to help laboratories evaluate their analytical capability. This exercise was carried out in the framework of the Analytical Quality Control Services Programme of the International Atomic Energy Agency. 95 laboratories expressed their willingness to participate in this exercise. Each of these laboratories was given a code number and received four water samples prepared by IAEA. These were marked as OH-5, OH-6, OH-7, and OH-8 and designed such that they cover the typical natural range of δ18O and δ2H values. The IAEA Isotope Hydrology Laboratory itself carefully calibrated the stable isotopic composition of these water samples by performing a large number of analyses (about 80 for each sample) spread over a period of 5 months using two mass-spectrometers and associated gas extraction systems. The rounded IAEA reference values are given below for OH-5, OH-6, OH-7 and OH-8: -0.20, -4.16, -10.65, -16.20 per mille with average uncertainties of ±0.03 per mille for δ18O; and for δ2H: -1.7, -38.7, -77.6, -121.5 per mille with average uncertainties of ±0.6 per mille. Those mean values obtained are used here as reference values for facilitating the inter-comparison. The laboratories were requested to report the δ-values on the normalised VSMOW-SLAP scale, together with the overall uncertainty at one sigma level. By the end of October 2002, 82

  11. Multiple tree-ring chronologies (ring width, δ13C and δ18O) reveal dry and rainy season signals of rainfall in Indonesia

    Schollaen, Karina; Heinrich, Ingo; Neuwirth, Burkhard; Krusic, Paul J.; D'Arrigo, Rosanne D.; Karyanto, Oka; Helle, Gerhard

    2013-08-01

    Climatic hazards, such as severe droughts and floods, affect extensive areas across monsoon Asia and can have profound impacts on the populations of that region. The area surrounding Indonesia, including large portions of the eastern Indian Ocean and Java Sea, plays a key role in the global climate system because of the enormous heat and moisture exchange that occurs between the ocean and atmosphere there. Here, we evaluate the influence of rainfall variability on multiple tree-ring parameters of teak (Tectona grandis) trees growing in a lowland rain forest in Central Java (Indonesia). We assess the potential of, annually resolved, tree-ring width, stable carbon (δ13C) and oxygen (δ18O) isotope records to improve our understanding of the Asian monsoon variability. Climate response analysis with regional, monthly rainfall data reveals that all three tree-ring parameters are significantly correlated to rainfall, albeit during different monsoon seasons. Precipitation in the beginning of the rainy season (Sep-Nov) is important for tree-ring width, confirming previous studies. Compared to ring width, the stable isotope records possess a higher degree of common signal, especially during portions of the peak rainy season (δ13C: Dec-May; δ18O: Nov-Feb) and are negatively correlated to rainfall. In addition, tree-ring δ18O also responds positively to peak dry season rainfall, although the δ18O rainy season signal is stronger and more time-stable. The correlations of opposite sign reflect the distinct seasonal contrast of the δ18O signatures in rainfall (18OPre) during the dry (18O-enriched rain) and rainy (18O-depleted rain) seasons. This difference in 18OPre signal reflects the combination of two signals in the annual tree-ring δ18O record. Highly resolved intra-annual δ18O isotope analyses suggest that the signals of dry and rainy season can be distinguished clearly. Thereby reconstructions can improve our understanding of variations and trends of the

  12. An early Pleistocene Mg/Ca-δ18O record from the Gulf of Mexico: Evaluating ice sheet size and pacing in the 40-kyr world

    Shakun, J. D.; Raymo, M. E.; Lea, D. W.; Klinkhammer, G. P.

    2011-12-01

    Two decades ago, Joyce (1993) presented a planktonic δ18O record from ODP site 625 in the Gulf of Mexico and interpreted numerous light isotope excursions beginning at 2.5 Ma as reflecting Laurentide Ice Sheet meltwater pulses down the Mississippi River. This finding implied an extensive early Pleistocene (EP) ice sheet, seemingly at odds with the smaller global ice volume inferred from benthic δ18O at this time. The till record on land confirms that ice extended into the central U.S at least twice during the EP. We are developing a high-resolution paired Mg/Ca-δ18O record from site 625 to reconstruct sea surface temperatures and salinity over the EP and evaluate Joyce's meltwater interpretation. Initial results of our temperature-corrected δ18O record confirm his inference of large meltwater spikes at the onset of the Quaternary. Our approach could weigh in on several hypotheses concerning the size and pacing of Quaternary ice sheets. The Integrated Insolation hypothesis explains the puzzling lack of precession variability in marine δ18O during the 40-kyr world by arguing that ice sheets are sensitive to insolation integrated over the summer, which is largely controlled by obliquity. The Antiphase Hypothesis, on the other hand, suggests that EP precession variability was antiphased between northern and southern ice sheets, canceling out and leaving the in-phase obliquity component to dominate the marine δ18O record. This view implies that marine δ18O may underestimate Northern Hemisphere ice volume during the EP. The Regolith Hypothesis takes the small ice volume implied by marine δ18O at face value and, together with the large ice area suggested from Joyce's meltwater spikes and the mid-continent till record, argues that EP ice sheets had a flat-like-a-pancake geometry, which it attributes to fast ice flow over a deformable bed. Erosion of this bed in the mid-Pleistocene may then have led to larger, more sluggish ice sheets and the transition from 40 to

  13. Temporal variations of atmospheric water vapor δD and δ18O above an arid artificial oasis cropland in the Heihe River Basin

    Wen, Xue-Fa

    2015-04-01

    The high temporal resolution measurements of δD, δ18O, and deuterium excess (d) of atmospheric water vapor provide an improved understanding of atmospheric and ecohydrological processes at ecosystem to global scales. Isotope ratio infrared spectroscopy has recently allowed high-frequency in situ measurements of atmospheric water vapor isotopic ratios in China (Wen et al., 2008, Journal of Hydrology; Wen et al., 2012, Journal of Atmospheric and Oceanic Technology). For our group, in situ and continuous observations of δD, δ18O, and d of atmospheric water vapor have been performed at the surface air in Beijing (Wen et al., 2010, Journal of Geophysical Research-Atmospheres; Zhange et al., 2011, Journal of Geographical Sciences), a winter wheat and summer maize cropland in Luancheng (Wen et al., 2012, Oecologia; Xiao et al., 2012, Global Change Biology), a grassland in Duolun (Hu et al., 2014, Journal of Geophysical Research- Biogeosciences), a spring maize cropland (Huang and Wen, 2014, Journal of Geophysical Research-Atmospheres) and a subtropical coniferous plantation (Yang et al., 2015, Agricultural and Forest Meteorology). In this study (Huang and Wen, 2014), δD, δ18O, and d of water vapor and their flux ratios were continuously measured from May to September 2012 using an in situ technique above an arid artificial oasis in the Heihe River Basin, which has a typical continental arid climate. The monthly δD and δ18O increased slowly and then decreased, whereas the monthly d showed a steady decrease. δD, δ18O, and d exhibited a marked diurnal cycle, indicating the influence of the entrainment, local evapotranspiration (ET), and dewfall. The departures of δD, δ18O, and d from equilibrium prediction were significantly correlated with rain amount, relative humidity (RH), and air temperature (T). The "amount effect" was observed during one precipitation event. δD and δ18O were log linear dependent on water vapor mixing ratio with respective R2 of 17% and

  14. A study of transport phenomena in the corrosion products of ferrous archaeological artefacts using 18O tracing and nuclear microprobe analysis

    Studies of ferrous archaeological artefacts corroded in soil are of great interest for the cultural heritage community and for the prediction of very long term corrosion behaviour of low alloy steels. One important hypothesis of recent studies is that corrosion mechanisms seem to be controlled by oxygen diffusion that is solved in the soil water and in the porosities of the corrosion products. Consequently, cathodic and anodic corrosion reactions should happen at the metal/oxide interface. In order to verify this assertion, several experiments were done using 18O tracers, to visualize where the corrosion reactions take place in the system. Samples collected on archaeological ferrous artefacts were put with their already formed corrosion products in water previously deoxygenised and equilibrated with 18O at a pressure of 1.2 atm. After various exposition periods, samples were removed and transverse sections were made. The distribution of the remaining18O precipitated product in the ancient corrosion products was mapped by means of the 18O(p,α)15N reaction. Indeed, this 18O presence seems to reveal the precipitation of new oxidation products and confirm the location of the cathodic reaction at the metal/oxide interface

  15. 低δ18O岩浆岩的成因%On the origin of low δ18O magmatic rocks

    张少兵; 郑永飞

    2011-01-01

    silicate rocks. Decades of geochemical studies on two classical cases of low δ18O magmas, Yellowstone rhyolites and Iceland basalts, have demonstrated that the mechanism to form the low δ18O magmas is through the partial melting of low δ18O rocks or the assimilation of normal δ18O magmas by low δ18O rocks during magma emplacement In either case, there are preexisting low δ18O rocks prior to the low δ18O magmatism. The low δ18O rocks can be generated by high-T hydrothermal alteration of surface water (seawater or meteoric water). The low δ18O magmatism usually takes place in rifting tectonic zones, with development of caldera collapse and subsequent remelting of low δ18O rocks. The granites at Seychelles in Indian Ocean and Nianzhishan in Northeast China represent two examples of low δ18O granites crystallized from low δ18O magmas. Their formation calls for the involvement of l8O-depleted materials in the magma source. The extent of l8O-depletion in the Dabie-Sulu metamorphic rocks and their extensive occurrences is very remarkable. The most negative δ18O rock-forming minerals were found in granite in the Dabie orogen, but with positive δ18O values for zircons of Neoproterozoic U-Pb ages. It is inferred that the low δ18O granite would have experienced two-stage water-rock interaction at high temperatures. The first leads to the formation of low δ18O magma and thus the crystallization of low δ18O zircons, and the second is characterized by the high-T meteoric-hydrothermal alteration and thus the further decrease of δ18O values for rock-forming minerals. More studies on the low δ18O granites, particularly microscale in-situ oxygen isotope analyses, will be helpful to the understanding of the mechanism of low δ18O magmatism. This can place basic geochemical constraints on the elements and isotopes behavior in the proceses of water-rock interaction.

  16. Intra-annual variations of teak cellulose δ18O in Kerala, India: implications to the reconstruction of past summer and winter monsoon rains

    Managave, S. R.; Sheshshayee, M. S.; Bhattacharyya, A.; Ramesh, R.

    2011-08-01

    A seasonal cycle has been observed in the high and coarse resolution intra-annual analyses of oxygen isotopic composition (δ18O) of teak ( Tectona grandis) cellulose from southern India, that receives both the south-west (SW) (summer) and the north-east (NE) (winter, more depleted in 18O) monsoon rains. The seasonal cycle as recorded by teak, with an amplitude between 1 and 3‰, shows lower δ18O values at the early and late growing seasons than at the middle. This pattern is opposite to that found in central Indian teak, nurtured mostly by the SW monsoon rain. A comparison of the observed and modeled intra-annual profiles reveals that the observed pattern of intra-annual δ18O variation in southern India is explainable only if teak trees had sampled rainfall from both the monsoons. Thus it appears possible to detect years of past excess NE monsoon rains by analyzing the δ18O of cellulose from the latewood of teak trees growing in Kerala, southern India.

  17. Intra-annual variations of teak cellulose {delta}{sup 18}O in Kerala, India: implications to the reconstruction of past summer and winter monsoon rains

    Managave, S.R. [Physical Research Laboratory, Ahmedabad (India); Pondicherry University, Department of Earth Sciences, Puducherry (India); Sheshshayee, M.S. [University of Agricultural Sciences, Bangalore (India); Bhattacharyya, A. [Birbal Sahani Institute of Palaeobotany, Lucknow (India); Ramesh, R. [Physical Research Laboratory, Ahmedabad (India)

    2011-08-15

    A seasonal cycle has been observed in the high and coarse resolution intra-annual analyses of oxygen isotopic composition ({delta}{sup 18}O) of teak (Tectona grandis) cellulose from southern India, that receives both the south-west (SW) (summer) and the north-east (NE) (winter, more depleted in {sup 18}O) monsoon rains. The seasonal cycle as recorded by teak, with an amplitude between 1 and 3 permille, shows lower {delta}{sup 18}O values at the early and late growing seasons than at the middle. This pattern is opposite to that found in central Indian teak, nurtured mostly by the SW monsoon rain. A comparison of the observed and modeled intra-annual profiles reveals that the observed pattern of intra-annual {delta}{sup 18}O variation in southern India is explainable only if teak trees had sampled rainfall from both the monsoons. Thus it appears possible to detect years of past excess NE monsoon rains by analyzing the {delta}{sup 18}O of cellulose from the latewood of teak trees growing in Kerala, southern India. (orig.)

  18. Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques

    Brand, Willi A.; Coplen, Tyler B.; Aerts-Bijma, Anita T.; Böhlke, J.K.; Gehre, Matthias; Geilmann, Heike; Groning, Manfred; Jansen, Henk G.; Meijer, Harro A. J.; Mroczkowski, Stanley J.; Qi, Haiping; Soergel, Karin; Stuart-Williams, Hilary; Weise, Stephan M.; Werner, Roland A.

    2009-01-01

    Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high-temperature conversion techniques (HTC)a in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125‰, an artificially enriched reference water (δ18O of +78.91‰) and two barium sulfates (one depleted and one enriched in 18O) were prepared and calibrated relative to VSMOW2b and SLAP reference waters. These materials were used to calibrate the other isotopic reference materials in this study, which yielded: Reference materialδ18O and estimated combined uncertainty c IAEA-602 benzoic acid

  19. Monthly sea surface temperature records reconstructed by δ18O of reef-building coral in the east of Hainan Island,South China Sea

    何学贤; 刘敦一; 彭子成; 刘卫国

    2002-01-01

    Stable oxygen isotopic compositions of a coral colony of Porites lutea obtained on a core allowed the reconstruction of a 56-a (1943-1998) proxy record of the sea surface temperatures. This coral δ18O data are from the east of Hainan Island water (22°20′N, 110°39′E), South China Sea. The relationship between δ18O in the skeletal aragonite carbonate and the sea surface temperature (SST) is SST = -5.36 δ18OPDB-3.51 (r = 0.73, n = 470), dδ18O/d(SST) = -0.187‰/ ℃; and the thermometer was set at monthly resolution. The 56-a (1943-1998) proxy record of the sea surface temperatures reflected the same change trend in the northern part of South China Sea as the air temperature change trend in China.

  20. An inexpensive auto-injection preprocessing system for N2O by isotope ratio mass spectrometer to measure δ15N and δ18O of nitrate

    Nitrogen and oxygen isotope ratios (δ15N, δ18O) of nitrate have been measured by denitrifier method aiming to analyze N material flows and their sources (ocean, lake, river, and groundwater). The denitrifier method developed in 1990s allows us to measure both δ15N and δ18O of nitrate simultaneously employing small amounts (i.e. 30nmol). The instruments including online auto-injection of N2O gas are still expensive(generally cost more than two hundred thousand US$). Here, we have developed a self-made auto-injection system of N2O to IRMS connected to the interface(Conflo III). This self-made system is inexpensive(i.e. twenty thousand US$) and has equal precisions of δ15N and δ18O with the past systems. (author)

  1. Discrimination against C18O16O during photosynthesis and the oxygen isotope ratio of respired CO2 in boreal forest ecosystems

    Our objective was to analyze factors that influence changes in the oxygen isotope ratio (δ18O) of atmospheric CO2 within boreal forest ecosystems. We made measurements in the three major forest types (black spruce, jack pine, and aspen) at the southern and northern ends of the boreal forest in central Canada. This research was part of a larger study, the Boreal Ecosystem-Atmosphere Study (BOREAS). In terrestrial ecosystems the δ18O value of atmospheric CO2 is strongly influenced by isotope effects that occur during photosynthesis and respiration. Of primary importance is an equilibrium isotope effect that occurs between oxygen in CO2 and oxygen in soil water and plant chloroplast water. During the equilibrium reaction the oxygen isotope ratio of CO2 becomes enriched in 18O relative to that of water. We measured seasonal changes in the oxygen isotope ratio of (1) water input to the ecosystems (precipitation), (2) water taken up by the major plant species from the soil (plant stem water), and (3) water in plant leaves. We used this information in calculations of isotope discrimination during photosynthesis and soil respiration. Discrimination against C18O16O during photosynthetic gas exchange (ΔA) (influenced by equilibration with chloroplast water) averaged approximately 21‰ at midday and was similar for all forest types. In contrast, CO2 released during plant and soil respiration had an average δ18O value of −14.4‰ but was less depleted in 18O than would be expected for respired CO2 in isotopic equilibrium with soil water. This effect was most pronounced in black spruce sites because of the extensive coverage of moss on the ground surface and the observation that water in the upper moss layers can have an oxygen isotope ratio substantially different from water in deeper soil layers. (author)

  2. Discrimination against C18O16O during photosynthesis and the oxygen isotope ratio of respired CO2 in boreal forest ecosystems

    Flanagan, Lawrence B.; Brooks, J. Renee; Varney, Gregory T.; Ehleringer, James R.

    1997-03-01

    Our objective was to analyze factors that influence changes in the oxygen isotope ratio (δ18O) of atmospheric CO2 within boreal forest ecosystems. We made measurements in the three major forest types (black spruce, jack pine, and aspen) at the southern and northern ends of the boreal forest in central Canada. This research was part of a larger study, the Boreal Ecosystem-Atmosphere Study (BOREAS). In terrestrial ecosystems the δ18O value of atmospheric CO2 is strongly influenced by isotope effects that occur during photosynthesis and respiration. Of primary importance is an equilibrium isotope effect that occurs between oxygen in CO2 and oxygen in soil water and plant chloroplast water. During the equilibrium reaction the oxygen isotope ratio of CO2 becomes enriched in 18O relative to that of water. We measured seasonal changes in the oxygen isotope ratio of (1) water input to the ecosystems (precipitation), (2) water taken up by the major plant species from the soil (plant stem water), and (3) water in plant leaves. We used this information in calculations of isotope discrimination during photosynthesis and soil respiration. Discrimination against C18O16O during photosynthetic gas exchange (ΔA) (influenced by equilibration with chloroplast water) averaged approximately 21‰ at midday and was similar for all forest types. In contrast, CO2 released during plant and soil respiration had an average δ18O value of -14.4‰ but was less depleted in 18O than would be expected for respired CO2 in isotopic equilibrium with soil water. This effect was most pronounced in black spruce sites because of the extensive coverage of moss on the ground surface and the observation that water in the upper moss layers can have an oxygen isotope ratio substantially different from water in deeper soil layers.

  3. Report on the supply and demand of 18O enriched water. Ad hoc committee of the North American Society for the Study of Obesity, 21 January 1999

    Oxygen-18 is a stable isotope that is used as a tracer for several biomedical applications. The two primary applications are the study of organismal energy expenditure and organ specific utilization of glucose. The former uses 18O along with deuterium to measure carbon dioxide production of free-living animals and humans. Total energy expenditure is calculated from carbon dioxide production using the standard equations of indirect calorimetry. The later uses 18O as a precursor for the production of 18F, a radionuclide that is incorporated into glucose homologues and injected into the circulating blood. When the glucose homologues are taken up by an organ (usually brain), the organ can be imaged using positron emission tomography (PET). Both of these techniques have become major research and, in the case of PET, diagnostic tools during the last decade. This growth in the use of these tools has increased the world-wide demand for 18O in the form of water. In 1998, this demand could not be met by suppliers and significant delivery delays have been encountered by many investigators and clinicians. Some suppliers are quoting delivery delays of a year. These delays have disrupted on-going research and delayed the start of new projects. The shortage has resulted in a price increase of nearly 50% in 18O water. The disruption of 18O supply in 1998 is the second such disruption in the past decade. Commercial suppliers could not provide sufficient product in late 1990 following the forced closure of the US government production facility at Los Alamos Laboratory. Delivery delays lasted throughout 1991. In August of 1998, the council of the North American Association for the Study of Obesity formed an ad hoc committee to gather information regarding the supply and demand for 18O and to investigate potential solutions to the problem

  4. Low-frequency noise in δ13C and δ18O tree ring data: A case study of Pinus uncinata in the Spanish Pyrenees

    Esper, Jan; Frank, David C.; Battipaglia, Giovanna; Büntgen, Ulf; Holert, Christopher; Treydte, Kerstin; Siegwolf, Rolf; Saurer, Matthias

    2010-12-01

    Isotopic discrimination measurements in tree rings are becoming increasingly important estimators of past environmental change. Potential biases inherent to these parameters, including age trend and level offset are, however, not well understood. We here perform measurements on a new millennium-long data set of decadally resolved δ18O and δ13C discrimination from 25 high-elevation pine trees in the Spanish Pyrenees to investigate whether such low-frequency biases exist and how they alter the long-term behavior of derived time series. Alignment of the tree ring data by biological age reveals age trends over the first one to four centuries after germination. On average, isotope values change by -0.089‰ δ18O and +0.064‰ δ13C per decade over the first 100 years of tree growth. This trend persists into the forth century after germination for δ18O but diminishes to ˜0‰ over the 100-390 year period for δ13C. We also find level offsets up to 7‰ δ18O and 3‰ δ13C between single trees. Analysis of the shape of age trends reveals negative exponential functions as reasonable choices for detrending of δ18O and (inverted) δ13C time series. The detrended isotope chronologies share low-frequency variance with traditional ring width and density measurements beyond statistical chance, suggesting that the various parameters reflect some of the same environmental forcing. Our results show that δ18O and δ13C from these Spanish pines need to be detrended to assess long-term environmental changes. To evaluate the general applicability of this conclusion, production of (1) well-replicated, (2) nonpooled, and (3) composite chronologies from other species and regions will be required. Increases in measurement speed and technology will make these tests feasible in the coming years.

  5. Elastic and inelastic scattering of [sup 16]O and [sup 18]O ions from [sup 64]Zn at energies near the Coulomb barrier

    Salem-Vasconcelos, S.; Takagui, E.M.; Bechara, M.J.; Koide, K.; Dietzsch, O. (Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil)); Jr, A.B.N. (Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro (Brazil)); Takai, H. (Brookhaven National Laboratory, Upton, New York 11973 (United States))

    1994-08-01

    Coulomb-nuclear interference effects were investigated in the inelastic scattering of [sup 16]O and [sup 18]O by [sup 64]Zn. Measurements of elastic and inelastic angular distributions of [sup 18]O were performed at a laboratory energy of 49 MeV, over the angular range from [theta][sub lab][similar to]30[degree] to 85[degree]. The excitation functions of [sup 16]O and [sup 18]O ions were measured at incident energies between 29 and 46 MeV at [theta][sub lab]=174[degree]. The experimental angular distributions show structures which are more pronounced for projectile excitation than for target excitation. The interference minimum for the excitation of the [sup 18]O first 2[sup +] state was found to be shifted towards forward angles by approximately 5[degree] (c.m.) with respect to the distorted-wave Born approximation calculations and by approximately 3.5[degree] (c.m.) with respect to the coupled-channels calculations. A pronounced Coulomb-nuclear interference minimum was seen in the excitation of [sup 64]Zn(2[sup +]) state by inelastic scattering of [sup 16]O projectiles, whereas no pronounced minimum was observed in target excitation by [sup 18]O projectiles. The elastic scattering data were analyzed with the optical model. The inelastic differential cross sections for the excitation of the first 2[sup +] states in the target and in the [sup 18]O projectile were analyzed using the distorted-wave Born approximation and also the coupled-channels approach with collective form factors.

  6. Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy I: Insight from a climate chamber experiment

    Zech, Michael; Mayr, Christoph; Tuthorn, Mario; Leiber-Sauheitl, Katharina; Glaser, Bruno

    2014-02-01

    The oxygen isotopic composition of cellulose is a valuable proxy in paleoclimate research. However, its application to sedimentary archives is challenging due to extraction and purification of cellulose. Here we present compound-specific δ18O results of hemicellulose-derived sugar biomarkers determined using gas chromatography-pyrolysis-isotope ratio mass spectrometry, which is a method that overcomes the above-mentioned analytical challenges. The biomarkers were extracted from stem material of different plants (Eucalyptus globulus, Vicia faba and Brassica oleracea) grown in climate chamber experiments under different climatic conditions. The δ18O values of arabinose and xylose range from 31.4‰ to 45.9‰ and from 28.7‰ to 40.8‰, respectively, and correlate highly significantly with each other (R = 0.91, p hemicellulose-derived sugar biomarkers, like cellulose, reflect the oxygen isotopic composition of plant source water altered by climatically controlled evapotranspirative 18O enrichment of leaf water. While relative air humidity controls most rigorously the evapotranspirative 18O enrichment, the direct temperature effect is less important. However, temperature can indirectly exert influence via plant physiological reactions, namely by influencing the transpiration rate which affects δ18Oleaf water due to the Péclet effect. In a companion paper (Tuthorn et al., this issue) we demonstrate the applicability of the hemicellulose-derived sugar biomarker δ18O method to soils and provide evidence from a climate transect study confirming that relative air humidity exerts the dominant control on evapotranspirative 18O enrichment of leaf water. Finally, we present a conceptual model for the interpretation of δ18Ohemicellulose records and propose that a combined δ18Ohemicellulose and δ2Hn-alkane biomarker approach is promising for disentangling δ18Oprecipitation variability from evapotranspirative 18O enrichment variability in future paleoclimate studies

  7. Millennial δ18O oscillations from a replicated Holocene speleothem record from Iberian Peninsula and hemispherical teleconecctions affecting the water cycle

    Domínguez-Villar, David; Wang, Xianfeng; Krklec, Kristina; Cheng, Hai; Edwards, R. Lawrence

    2016-04-01

    We present a speleothem δ18O record from Kaite Cave in northern Iberian Peninsula covering the last 9.7 ka BP. The record is constructed from four different stalagmites that replicate each other. The age model is based on 63 U-Th dates and over 4500 laminae providing a robust time frame for the record. The δ18O record has characteristic millennial oscillations through the Holocene with periodicity around 2 ka during the Late Holocene and around 1 ka during the Early Holocene. Causes of the millennial δ18O variability are not dominated by the amount of rainfall or atmospheric temperature and other controls of the water cycle are more relevant. The aquifer at this site filters any seasonal bias and speleothems records the inter-annual δ18O variability in precipitation. On the other hand, moisture source analysis at this site shows that significant amount of precipitation is from recycled moisture (continental origin). A variable proportion of this parameter is capable to impact significantly past values of δ18O in precipitation. Thus, we interpret the millennial oscillations of the δ18O record as changes in the hydrological cycle resulting from variable percentages of the recycled precipitation over the Iberian Peninsula. We found that variable amount of recycled precipitation in Iberian Peninsula is related to the location of the Iceland Low pressure cell, although does not correlate with NAO index. Correlation of Kaite δ18O record during the Holocene with other representative records suggests that millennial oscillations are caused by variability of the Gulf Stream/North Atlantic Current that affects atmospheric pressure fields in the North Atlantic. Further correlation of Kaite δ18O record along the world supports that the recorded millennial oscillations of the water cycle are related to persistent variability on the tropical North Atlantic. Only during periods of major sea-ice variability in high-latitudes of the North Atlantic, the later region replaces

  8. Syn-volcanic cannibalisation of juvenile felsic crust: Superimposed giant 18O-depleted rhyolite systems in the hot and thinned crust of Mesoproterozoic central Australia

    Smithies, R. H.; Kirkland, C. L.; Cliff, J. B.; Howard, H. M.; Quentin de Gromard, R.

    2015-08-01

    Eruptions of voluminous 18O-depleted rhyolite provide the best evidence that the extreme conditions required to produce and accumulate huge volumes of felsic magma can occur in the upper 10 km of the crust. Mesoproterozoic bimodal volcanic sequences from the Talbot Sub-basin in central Australia contain possibly the world's most voluminous accumulation of 18O-depleted rhyolite. This volcanic system differs from the better known, but geochemically similar, Miocene Snake River Plain - Yellowstone Plateau of North America. Both systems witnessed 'super' sized eruptions from shallow crustal chambers, and produced 18O-depleted rhyolite. The Talbot system, however, accumulated over a much longer period (>30 Ma), at a single depositional centre, and from a magma with mantle-like isotopic compositions that contrast strongly with the isotopically evolved basement and country-rock compositions. Nevertheless, although the Talbot rhyolites are exclusively 18O-depleted, the unavoidable inference of an 18O-undepleted precursor requires high-temperature rejuvenation of crust in an upper-crustal chamber, and in this respect the evolution of the Talbot rhyolites and 18O-depleted rhyolites of the Snake River Plain - Yellowstone Plateau is very similar. However, instead of older crustal material, the primary upper-crustal source recycled into Talbot rhyolites was comagmatic (or nearly so) felsic rock itself derived from a contemporaneous juvenile basement hot-zone. Whereas giant low δ18O volcanic systems show that voluminous melting of upper crust can occur, our studies indicate that felsic magmas generated at lower crustal depths can also contribute significantly to the thermal and material budget of these systems. The requirement that very high-temperatures be achieved and sustained in the upper crust means that voluminous low δ18O magmatism is rare, primarily restricted to bimodal tholeiitic, high-K rhyolite (A-type) magmatic associations in highly attenuated lithosphere. In the

  9. [Isotopic composition of the delta-18O--delta-13C from the otoliths of reef fish from Taiaro (Tuamotu, French Polynesia): isotopic and biological implications].

    Blamart, Dominique; Escoubeyrou, Karine; Juillet-Leclerc, Anne; Ouahdi, Rabia; Lecomte-Finiger, Raymonde

    2002-02-01

    Nuclei (larval stage) and outer parts (adult stage) of fish otoliths from the Taiaro closed lagoon (French Polynesia) and adjacent ocean have been analysed for the C-O isotopic compositions. delta 18O values of the nuclei of both populations indicate that isotopic equilibrium is reached. This implies that the lagoonal fish population has done its complete biological cycle in the lagoon and represents an adaptation in a closed system. delta 18O values of the outer parts show a slight isotopic disequilibrium (< 0.2@1000) interpreted in term of vital effect. All the delta 13C values exhibit a strong isotopic disequilibrium related to metabolic activity. PMID:11980181

  10. Interpretation of orbital scale variability in mid-latitude speleothem δ18O: Significance of growth rate controlled kinetic fractionation effects

    Stoll, Heather; Mendez-Vicente, Ana; Gonzalez-Lemos, Saul; Moreno, Ana; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence

    2015-11-01

    Oxygen isotopes have been the most widely used climate indicator in stalagmites, applied to reconstruct past changes in rainfall δ18O and cave temperature. However, the δ18O signal in speleothems may also be influenced by variable kinetic fractionation effects, here conceived broadly as fractionation effects not arising from temperature variation. The regional reproducibility of speleothem δ18O signals has been proposed as a way to distinguish the δ18O variations arising directly from changes rainfall δ18O and cave temperature, from variations due to kinetic effects which may nonetheless be influenced by climate. Here, we compare isotopic records from 5 coeval stalagmites from two proximal caves in NW Spain covering the interval 140 to 70 ka, which experienced the same primary variations in temperature and rainfall δ18O, but exhibit a large range in growth rates and temporal trends in growth rate. Stalagmites growing at faster rates near 50 μm/yr have oxygen isotopic ratios over 1‰ more negative than coeval stalagmites with very slow (5 μm/yr) growth rates. Because growth rate variations also occur over time within any given stalagmite, the measured oxygen isotopic time series for a given stalagmite includes both climatic and kinetic components. Removal of the kinetic component of variation in each stalagmite, based on the dependence of the kinetic component on growth rate, is effective at distilling a common temporal evolution of among the oxygen isotopic records of the multiple stalagmites. However, this approach is limited by the quality of the age model. For time periods characterized by very slow growth and long durations between dates, the presence of crypto-hiatus may result in average growth rates which underestimate the instantaneous speleothem deposition rates and which therefore underestimate the magnitude of kinetic effects. The stacked growth rate-corrected speleothem δ18O is influenced by orbital scale variation in the cave temperature and

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

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

    2016-04-01

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

  12. Circulation effect: response of precipitation δ18O to the ENSO cycle in monsoon regions of China

    Tan, Ming

    2014-02-01

    Inter-annual variation in the ratio of 18O to 16O of precipitation (δ18Op) in the monsoon regions of China (MRC, area approximately east of 100°E) has not yet been fully analyzed. Based on an analysis of the relationships between the time series of amount-weighted mean annual δ18O in precipitation (δ18Ow) and meteorological variables such as temperature, precipitation as well as atmospheric/oceanic circulation indices, it is recognized that the El Niño-Southern Oscillation (ENSO) cycle appears to be the dominant control on the inter-annual variation in δ18Op in the MRC. Further analysis shows that the trade wind plays a role in governing δ18Ow through affecting the intensity of the different summer monsoon circulations which are closely linked to the weakening (weaker than normal) and strengthening (stronger than normal) of the trade wind and gives the δ18Ow different values at or over inter-annual timescales. The southwest monsoon (SWM) drives long-distance transport of water vapor from Indian Ocean to the MRC, and along this pathway increasing rainout leads to more negative δ18Ow via Rayleigh distillation processes. In contrast, the southeast monsoon (SEM), which is consistent with the changes in the strength of the West Pacific subtropical high, drives short-distance water vapor transport from the West Pacific Ocean to the MRC and leads to less negative δ18Ow. Therefore, the δ18Ow value directly reflects the differences in influence between the SWM, which is strong when the SE trade wind is strong, and the SEM, which is strong when the SE trade wind is weak. In addition, the South China Sea Monsoon also transports local water vapor as well as plays a role in achieving the synchronization between the δ18Ow and ENSO. The author thus terms the δ18Op rhythm in the MRC the "circulation effect". In turn, the δ18Op variation in the MRC has the potential to provide information on atmospheric circulation and the signal of δ18Op recorded in natural archives

  13. Down Core Oxygen Isotopic Measurements Of Diatom δ18O From The Guaymas Basin, Gulf Of California

    Menicucci, A. J.; Spero, H. J.; Thunell, R.

    2015-12-01

    The Guaymas Basin (GB), Gulf of California (27º53'N, 111º40'W ), is an evaporative basin, with sea surface temperatures (SST) varying between ~30oC (summer) and ~15oC (winter). Productivity is controlled mostly by seasonal upwelling starting in fall (early November) and extending into spring. We are currently analyzing δ18Odiatom from a boxcore (BC-43) using microfluorination (Menicucci, et al. 2013). This boxcore was previously analyzed for UK '37 alkenones and 210Pb activity (Goni, et al. 2001). Residual BC-43 material was sampled at ~2cm intervals. Samples were cleaned to isolate diatoms from other sediments, then equilibrated in water with δ18Owater = +85‰ for 70 hours at 21oC prior to vacuum dehydroxylation and microfluorination. The latter equilibration was done to account for fractionation between covalently bound O and OH- groups during vacuum dehydroxylation, preserving the original δ18Odiatom value. We present δ18Odiatom data from BC-43 samples covering 27cm, equivalent to >225 years of sediment accumulation. δ18O data are converted to temperature (T) based on an existing calibration (Leclerc and Labeyrie 1987). Our data suggest δ18Odiatom values record a T range of 22-18oC, corresponding to the mixed layer depth and the chlorophyll maximum during the fall bloom. These T values are offset from SST data by a mean of 5oC for the same sample intervals. However, δ18Odiatom values from the most recent samples suggest a ~2oC increase in diatom T relative to SST during the last 35 years. This subsurface warming may be due to decreased fall upwelling, increased mixed layer and chlorophyll maximum depths, and/or the timing of the peak diatom bloom. Such correlations are being investigated and the latest results will be presented. Goni, M. A., et al. (2001). Oceanographic considerations for the application of the alkenone-based paleotemperature U-37(K ') index in the Gulf of California. Geochimica Et Cosmochimica Acta 65: 545-557. Leclerc, A. J. and L

  14. Recoil-range studies of heavy products of multinucleon transfer from 18O to 245Cm and 249Cf

    Recoil range distributions were measured for alpha and spontaneous fission activities made in the bombardment of 245Cm and 249Cf with 18O from 6.20 MeV/nucleon down to the interaction barrier. The shape of the distributions indicates tht transfers of up to four protons take place via a combination of quasi-elastic (QET) and deep inelastic (DIT) mechanisms, rather than complete fusion-de-excitation (CF) or massive transfer (MT). Angular distributions constructed from recoil range distributions, assuming QET/DIT, indicate that the QET component contributes more significantly to the heavy product residue cross section than the DIT, even though primary cross sections are expected to be higher for DIT than for QET. This may be explained qualitatively as a result of the high excitation energies associated with DIT; the very negative Q/sub gg/ of projectile stripping for these systems combined with the lower expected optimal Q/sub rxn/ of QET compared to DIT can give QET products comparatively low excitation

  15. Impact of Source Region on the delta18 O signal in snow: A case study from Mount Wrangell Alaska

    Moore, G.W.K.; Field, Robert D.; Benson, Carl S.

    2016-01-01

    The stable isotopic composition of water in ice cores is an important source of information on past climate variability. At its simplest level, the underlying assumption is that there is an empirical relationship between the normalized difference in the concentration for these stable isotopes and a specified local temperature at the ice core site. There are, however, nonlocal processes, such as a change in source region or a change in the atmospheric pathway, which can impact the stable isotope signal, thereby complicating its use as a proxy for temperature. In this paper, the importance of these nonlocal processes are investigated through the analysis of the synoptic-scale circulation during a snowfall event at the summit of Mount Wrangell (62 deg N, 144 deg W; 4300 m MSL) in south-central Alaska. During this event there was, over a 1-day period in which the local temperature was approximately constant, a change in delta18 O that exceeded half that normally seen to occur in the region between summer and winter. As shall be shown, this arose from a change in the source region, from the subtropical eastern Pacific to northeastern Asia, for the snow that fell on Mount Wrangell during the event.

  16. Isotopic composition (δ18O and δD) of the shallow groundwater in the Poyang Lake basin

    Soldatova, E. A.; Sun, Z.; Guseva, N. V.

    2016-03-01

    The article is focused on the identification of evaporation and other natural processes which affect the isotopic composition of shallow groundwater in the Poyang Lake basin, such as water-rock interaction and mixing of the shallow groundwater and surface water. For this purpose the dual isotope approach (δD–H2O and δ18O–H2O) was used. The samples were collected from domestic wells around the Poyang Lake. The value of δD obtained for the shallow groundwater ranges from -21.5 to -42.6∘/∘∘. The δ18O value varies from -3.5 to -7.1∘/∘∘. It was found that the shallow groundwater of the Poyang Lake catchment is of meteoric origin. The influence of evaporation on the isotopic composition of shallow groundwater is negligible and observed mainly during the dry season. The deviation from the local meteoric water line, especially during the rainy season, may be explained by the processes in the water-rock system, but this issue is required further research.

  17. The JCMT Legacy Survey of the Gould Belt: mapping 13CO and C18O in Orion A

    Buckle, J V; Di Francesco, J; Graves, S F; Nutter, D; Richer, J S; Roberts, J F; Ward-Thompson, D; White, G J; Brunt, C; Butner, H M; Cavanagh, B; Chrysostomou, A; Curtis, E I; Duarte-Cabral, A; Etxaluze, M; Fich, M; Friberg, P; Friesen, R; Fuller, G A; Greaves, J S; Hatchell, J; Hogerheijde, M R; Johnstone, D; Matthews, B; Matthews, H; Rawlings, J M C; Sadavoy, S; Simpson, R J; Tothill, N F H; Tsamis, Y G; Viti, S; Wouterloot, J G A; Yates, J

    2012-01-01

    The Gould Belt Legacy Survey will map star-forming regions within 500 pc, using HARP (Heterodyne Array Receiver Programme), SCUBA-2 (Submillimetre Common-User Bolometer Array 2) and POL-2 (Polarimeter 2) on the James Clerk Maxwell Telescope (JCMT). This paper describes HARP observations of the J = 3-2 transitions of 13CO and C18O towards Orion A. The 1500-resolution observations cover 5 pc of the Orion filament, including OMC1 (inc. BN-KL and Orion Bar), OMC 2/3 and OMC 4, and allow a comparative study of the molecular gas properties throughout the star-forming cloud. The filament shows a velocity gradient of ~1 km/s /pc between OMC 1, 2 and 3, and high velocity emission is detected in both isotopologues. The Orion Nebula and Bar have the largest masses and line widths, and dominate the mass and energetics of the high velocity material. Compact, spatially resolved emission from CH3CN, 13CH3OH, SO, HCOOCH3, C2H5OH, CH3CHO and CH3OCHO is detected towards the Orion Hot Core. The cloud is warm, with a median exci...

  18. Study of ternary-component bismuth molybdate catalysts by 18O2 tracer in the oxidation of propylene to acrolein

    Participation of lattice oxide ions of ternary-component bismuth molybdate catalysts M-Bi-Mo-O (M = Ni, Co, Mg, Mn, Ca, Sr, Ba, and Pb) was investigated using the 18O2 tracer in the selective oxidation of propylene to acrolein. The participation of the lattice oxide ions in the oxidation is prominent on every catalyst but the extent of the participation varies significantly depending on the structure of the catalyst. Only lattice oxide ions in the bismuth molybdate phase are incorporated into the oxidized products on the catalysts (M = Ni, Co, Mg, and Mn) where M have smaller ionic radius than Bi3+; catalyst particles are composed of a shell of bismuth molybdates and a core of MMoO4. On the other hand, whole oxide ions in the active particles are involved in the oxidation on catalysts having a scheelite-type structure (M = Ca, Sr, Ba, and Pb) where M has a comparable ionic radius to Bi3+

  19. Effect of N/Z in pre-scission neutron multiplicity for 16,18O+198Pt systems

    This paper reports the summary of the experimental results of pre-scission neutron multiplicities from four compound nuclei, namely 210,212,214,216Rn, and statistical model analysis of the corresponding data. The compound nuclei 210,212,214,216Rn having N/Z values as 1.441, 1.465, 1.488, 1.511 respectively are populated through the 16,18O+194,198Pt reactions at excitation energies of 50, 61, 71.7 and 79 MeV. The measured neutron multiplicities are further analyzed with the statistical model of nuclear decay where fission hindrance due to nuclear dissipation is considered. The N/Z dependence of the dissipation strength at lowest excitation energy of the compound nuclei suggests shell closure effects. However, such effects are not observed at higher excitations where the variation of the dissipation strength with N/Z does not show any specific trend. The variation of N/Z in fission time scale is also shown. (authors)

  20. A coupled D/18O approach to reconstruct the paleohumidity during the Younger Dryas in the Eifel, Germany

    Wüthrich, Lorenz; Hepp, Johannes; Bromm, Tobias; Kathrin Schäfer, Imke; Zech, Jana; Sirocko, Frank; Zech, Michael; Zech, Roland

    2016-04-01

    Leaf waxes, such as long-chain n-alkanes and n-alkanoic acids, and their D/H isotopic composition, are increasingly used in lake, marine and eolian sediments to reconstruct past changes in vegetation, as well as the isotopic composition of precipitation. However, evaporative enrichment of leaf water might compromise such reconstructions, and it remains difficult to quantitatively reconstruct past climate changes. For the present study, we have analyzed samples from the Gemündener Maar, a lake situated in the western Eifel, Germany, for their isotopic composition of n-alkanes (D) and sugars (18O). Combination of both isotopes allows calculating not only the isotopic composition of paleo-precipitation, but also relative humidity (rh), based on reconstructed d-excess of leaf water. Our results suggest that the Younger Dryas was not particularly dry compared to the Alleröd. The onset of the Holocene, on the other hand, seems to have been very dry, except for one humid spell. Only with the transition Preboreal/Boreal, rh increased again.

  1. Study of the high resolution spectrum of 32S16O18O: The ν1 and ν3 bands

    Ulenikov, O. N.; Bekhtereva, E. S.; Krivchikova, Yu. V.; Zamotaeva, V. A.; Buttersack, T.; Sydow, C.; Bauerecker, S.

    2016-01-01

    The high resolution infrared spectrum of the 32S16O18O molecule was recorded for the first time with a Bruker IFS 120 HR Fourier transform interferometer in the region of 930-1580 cm-1 where the bands ν1 and ν3 are located. More than 3000 and about 2400 transitions were assigned in the experimental spectrum with the maximum values of quantum numbers Jmax. /Kamax. equal to 58/23 and 68/23 to the bands ν1 and ν3, respectively. The further weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account Coriolis resonance interaction between the vibrational states (100) and (001). The 81 microwave transitions of the states (100) and (001) known from the literature also were taken into account. As the result, a set of 26 fitted parameters was obtained which reproduces the experiment-based 2690 ro-vibrational energy values of the two bands with the drms = 1.8 ×10-4 cm-1. Microwave transitions are also reproduced with the accuracy close to experimental uncertainty.

  2. Model reconstruction of nitrate pollution of riverbank filtration using 15N and 18O data, Karany, Czech Republic

    Stable isotopes of O (δ18O) in water and N (δ15N) in NO3- have been used as natural indigenous groundwater tracers for sources of water and of NO3- at two riverbank filtration (RBF) water supply systems. Both RBF systems (Skorkov and Sojovice) have wells in unconsolidated Quaternary sediments close to the Jizera River (Czech Republic) that have been affected by increasing NO3- concentrations. The area is underlain by Turonian sandstones and marls that form a deeper bedrock aquifer. Sources of NO3- are local sewerage systems and landfills (point sources) and seasonal application of manure and inorganic fertilizers (diffuse sources). At RBF Skorkov recharge to wells can be modelled using a two-component model with 60% river water contribution and 40% of very shallow groundwater with an average residence time of one month. During periods of abundant precipitation, groundwater originates entirely from the unsaturated zone of the Quaternary aquifer; extensive pumping for over 40a has created new, bypassing flow paths that preferentially drain the contaminated unsaturated zone. During dry periods, wells are recharged by longer residence time groundwater from the Quaternary aquifer. At RBF Sojovice there is an additional recharge component of groundwater from the Turonian aquifer, which is sandier at this locality; this contains denitrified NO3- with highly positive δ15N values

  3. Palaeotemperature reconstruction during the Last Glacial from δ18O of earthworm calcite granules from Nussloch loess sequence, Germany

    Prud'homme, Charlotte; Lécuyer, Christophe; Antoine, Pierre; Moine, Olivier; Hatté, Christine; Fourel, François; Martineau, François; Rousseau, Denis-Didier

    2016-05-01

    The Nussloch loess-palaeosol sequence (Rhine Valley, Germany) is considered to be one of the most complete records of the last glacial period in Western Europe due to its very high sedimentation rate and its good chronological control. This sequence is therefore a good framework in which to develop new proxies for palaeoenvironmental reconstructions. In this study, we explore, for the first time, the potential of earthworm calcite granules as a new bio-indicator and climatic proxy of absolute air and soil temperature in the context of Last Glacial loess. These granules are composed of rhomboedric calcite crystals, organized in a radial crystalline structure. As these granules are individually generated by earthworms at a relative fast rate, they are expected to record intra-annual variations in the available sources of oxygen: percolating waters of meteoric origin. We extracted thirty earthworm calcite granules from 11 of 5 cm layers thick from tundra gley and brown soil horizons previously, dated at 45 to 23 ka. Oxygen isotope ratios were measured on each individual granule. The δ18O of calcite granules and interlinked transfer functions between water cycle, air and soil temperatures allowed us to estimate air temperatures ranging from 10 to 12 ± 4°C, which most likely reflect the warm periods of the year when earthworms were the most active.

  4. Human immunodeficiency virus-1 protease. 1. Initial velocity studies and kinetic characterization of reaction intermediates by 18O isotope exchange

    The peptidolytic reaction HIV-1 protease has been investigated by using four oligopeptide substrates, Ac-Ser-Gln-Asn-Pro-Val-Val-NH2, Ac-Arg-Ala-Ser-Gln-Asn-Tyr-Pro-Val-Val-NH2, Ac-Ser-Gln-Ser-Tyr-Pro-Val-Val-NH2, and Ac-Arg-Lys-Ile-Leu-Phe-Leu-Asp-Gly-NH2 that resemble two cleavage sites found within the naturally occurring polyprotein substrates Pr55gag and Pr160gag-pol. By use of a variety of inorganic salts, it was concluded that the peptidolytic reaction is nonspecifically activated by increasing ionic strength. V/K increased in an apparently parabolic fashion with increasing ionic strength, while V was either increased or decreased slightly. From product inhibition studies, the kinetic mechanism of the protease is either random or ordered uni-bi, depending on the substrate studied. The protease-catalyzed exchange of an atom of 18O from H218O into the re-formed substrates occurred at a rate which was 0.01-0.12 times that the forward peptidolytic reaction. The results of these studies are in accord with the formation of a kinetically competent enzyme-bound amide hydrate intermediate, the collapse of which is the rate-limiting chemical step in the reaction pathway

  5. Diagnosing Atmospheric Influences on the Interannual 18O/16O Variations in Western U.S. Precipitation

    Kei Yoshimura

    2013-07-01

    Full Text Available Many climate proxies in geological archives are dependent on the isotopic content of precipitation (δ18Op, which over sub-annual timescales has been linked to temperature, condensation height, atmospheric circulation, and post-condensation exchanges in the western U.S. However, many proxies do not resolve temporal changes finer than interannual-scales. This study explores causes of the interannual variations in δ18Op within the western U.S. Simulations with the Isotope-incorporated Global Spectral Model (IsoGSM revealed an amplifying influence of post-condensation exchanges (i.e., raindrop evaporation and vapor equilibration on interannual δ18Op variations throughout the western U.S. Mid-latitude and subtropical vapor tagging simulations showed that the influence of moisture advection on δ18Op was relatively strong in the Pacific Northwest, but weak over the rest of the western U.S. The vapor tags correlated well with interannual variations in the 18O/16O composition of vapor, an indication that isotopes in vapor trace atmospheric circulation. However, vertical-tagging simulations revealed a strong influence of condensation height on δ18Op in California. In the interior of the western U.S., a strong temperature effect was found only after annual mean temperatures were weighted by monthly precipitation totals. These multiple influences on δ18Op complicate interpretations of western U.S. climate proxies that are derived from isotopes in precipitation.

  6. The effect of acid rain and altitude on concentration, δ34S, and δ18O of sulfate in the water from Sudety Mountains, Poland

    Szynkiewicz, Anna; Modelska, Magdalena; Jedrysek, Mariusz Orion; Mastalerz, Maria

    2008-01-01

    The analyses of sulfate content, δ34S and δ18O of dissolved sulfate, and δ18O of water were carried out in a 14 km2 crystalline massif located in the Sudety Mountains (SW Poland) to 1) assess the amount of the sulfate delivered to the surface and groundwater systems by modern atmospheric precipitation, 2) determine the effect of altitude on these parameters, and 3) investigate their seasonal variations. In April and November of 2002, August 2003, and March and September of 2005, samples of water were collected from springs and streams of the massif. During these seasons, sulfate contents and δ18O(SO42−) values varied from 5.80 to 18.00 mg/l and from 3.96 to 8.23‰, respectively, showing distinctively higher values ofδ18O(SO42−) in wet seasons. The δ34S(SO42−) values had a relatively narrow range from 4.09 to 5.28‰ and were similar to those reported for organic matter in soil and the canopy throughfall in the Sudety Mountains.

  7. Punta Pitt Stable Isotope and Ion Data (delta 18O, delta 13C, Cd/Ca, Mn/Ca) for 1936 to 1982.5

    National Oceanic and Atmospheric Administration, Department of Commerce — File contains data presented by Shen et al. (1992a). Table includes d18O, d13C, Cd/Ca, Mn/Ca, and Ba/Ca data from a 2m coral head and, for comparison, SST records...

  8. Quasiclassical trajectory studies of 18O(3P) + NO2 isotope exchange and reaction to O2 + NO on D0 and D1 potentials

    Fu, Bina; Zhang, Dong H.; Bowman, Joel M.

    2013-07-01

    We report quasiclassical trajectory calculations for the bimolecular reaction 18O(3P) + NO2 on the recent potential energy surfaces of the ground (D0) and first excited (D1) states of NO3 [B. Fu, J. M. Bowman, H. Xiao, S. Maeda, and K. Morokuma, J. Chem. Theory. Comput. 9, 893 (2013)], 10.1021/ct3009792. The branching ratio of isotope exchange versus O2 + NO formation, as well as the product angular distributions and energy and rovibrational state distributions are presented. The calculations are done at the collision energy of relevance to recent crossed beam experiments [K. A. Mar, A. L. Van Wyngarden, C.-W. Liang, Y. T. Lee, J. J. Lin, and K. A. Boering, J. Chem. Phys. 137, 044302 (2012)], 10.1063/1.4736567. Very good agreement is achieved between the current calculations and these experiments for the branching ratio and final translational energy and angular distributions of isotope exchange products 16O(3P) + NO2 and O2 + NO formation products. The reactant 18O atom results in 18O16O but not N18O for the O2 + NO formation product channel, consistent with the experiment. In addition, the detailed vibrational and rotational state information of diatomic molecules calculated currently for the 34O2 + NO formation channel on D0 and D1 states are in qualitative agreement with the previous experimental and theoretical results of the photodissociation of NO3 and are consistent with older thermal bimolecular kinetics measurements.

  9. Drought history inferred from tree ring δ 13C and δ 18O in the central Tianshan Mountains of China and linkage with the North Atlantic Oscillation

    Xu, Guobao; Liu, Xiaohong; Qin, Dahe; Chen, Tuo; Sun, Weizhen; An, Wenling; Wang, Wenzhi; Wu, Guoju; Zeng, Xiaomin; Ren, Jiawen

    2014-05-01

    Annual tree ring δ 18O and δ 13C chronologies from 1790 to 2008 were established using Tianshan spruce ( Picea schrenkiana) in the central Tianshan Mountains of northwestern China. Temperature has a positive effect on tree ring δ 18O and δ 13C in the study area, while precipitation and relative humidity have negative effects. The standardized precipitation-evapotranspiration index (SPEI) considered all of these effects and was significantly negatively correlated with tree ring δ 18O and δ 13C. We combined the tree ring δ 18O and δ 13C series to reconstruct the past 192 years of SPEI, which accounted for about 46 % of the total variance of SPEI from 1950 to 2006. The reconstruction showed good spatial agreement with gridded data in Palmer Drought Severity Index and precipitation and an inverse relationship with temperature. Our SPEI reconstruction reveals several wet and dry periods over the past 192 years and has good agreement with other drought records. Wavelet analysis showed quasi-periodic 10-, 20-, 30-, and 70-year fluctuations in the reconstruction. The 10-, 20-, and 30-year periodicities may reflect the potential influence of North Atlantic Oscillation (NAO). Overall, this study indicates that the SPEI is a potential drought index, and the winter NAO affects regional moisture conditions in the long term.

  10. Two new inorganic-organic hybrid materials based on inorganic cluster, [X2Mo18O62]6− (X=P, As)

    Fatma Hmida; Meriem Ayed; Brahim Ayed; Amor Haddad

    2015-09-01

    Two new inorganic-organic hybrid materials based on heteropolyoxometalates, (C4H10N)6 (P2 Mo18O62).4H2O I, and (C4H10N)6 (As2Mo18O62).4H2O II, where C4H10N is protonated pyrrolidine have been synthesized and structurally characterized by physic-chemical methods. Single-crystal X-ray diffraction method, infrared, ultraviolet spectroscopy, Thermogravimetricanalysis andcyclic voltammetry measurements of the title hybrid materials indicate that there are hydrogen bond interaction between O atoms of the hetero-polyoxometalates and water molecules as well as the N and O atoms of the organic compound. The molecular structures of synthesized hybrid materials contain discrete entities of pyrrolidinumion and water molecules surround every [X2Mo18O62]6− anion over the extended crystalline network that the [X2Mo18O62]6− anion retains its ``Dawson structure". Crystal data: I monoclinic, space group P21/a, a = 13,453(1) Å, b = 24,046 (1) Å, c = 24,119(1) = 97, 99(1)°, V = 7726,30(5) Å3 and Z = 4; II monoclinic, space group P21/a, a = 13.4900(1) Å, 24.0900(1) Å, 24.2740(1) Å, = 98.320(1)°, V = 7805.40(7) Å3 and Z = 4.

  11. Comparative study of fusion barrier distribution in 16O and 18O induced reactions on 232Th and 209Bi targets

    In order to investigate the influence of projectile excitations and transfer channels, quasi-elastic excitation function measurements with 16,18O projectile on two targets, one heavy (232Th) and the other a lighter target (209Bi) at energies around their Coulomb barrier are investigated. The results are compared with a new CC code CCFULL

  12. Nucleosynthesis in AGB stars traced by isotopic ratios. I - Determining the stellar initial mass by means of the $^{17}$O/$^{18}$O ratio

    De Nutte, R; Olofsson, H; Lombaert, R; de Koter, A; Karakas, A; Milam, S; Ramstedt, S; Stancliffe, R J; Homan, W; Van de Sande, M

    2016-01-01

    The aim of this paper is to investigate the $^{17}$O/$^{18}$O ratio for a sample of AGB stars, containing M-, S- and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. This study is the first to explore these oxygen ratios for a sample covering the three spectral types. Circumstellar $^{13}$C$^{16}$O, $^{12}$C$^{17}$O and $^{12}$C$^{18}$O line observations were obtained for a sample of nine stars with various single-dish long-wavelength facilities. These data have been fully reduced and analyzed. The line intensity ratios obtained from these observations are then related directly to the surface $^{17}$O/$^{18}$O abundance ratio. Stellar evolution models predict the $^{17}$O/$^{18}$O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars less massive than 5 M$_{\\odot}$. This allows the measured ratio to function as an effective method of determining the ini...

  13. Evaluation of the effects of microscale chemical and isotopic heterogeneity of coral skeleton on conventional Sr/Ca and 18O paleothermometers

    Takehiro Mitsuguchi

    2013-10-01

    Recent studies using secondary ion mass spectrometry revealed microscale heterogeneity of Sr/Ca and 18O in shallow-water coral skeletons, i.e., Sr/Ca and 18O differ significantly between two basic microfeatures of the skeleton: the center of calcification (COC) and surrounding fibrous skeleton (SFS). The COC, in contrast with the SFS, consists of highly irregular crystals intermingled with significant amount of organic matter; therefore, analyzing the SFS only would probably be favourable for paleotemperature reconstruction. Conventional Sr/Ca and 18O paleothermometers are, however, based on the analysis of the mixture of the COC and SFS, and thus may be significantly affected by the above-mentioned heterogeneity. In this study, I have evaluated the heterogeneity-induced effects on the conventional paleothermometers of Porites skeletons using published Sr/Ca, 18O and volume-fraction data of the COC and SFS and published observations of seasonal variability of bulk skeletal density. Results indicate that the effects may yield significant or serious errors in paleotemperature reconstruction.

  14. Quantitation of peptides and proteins by matrix-assisted laser desorption/ionization mass spectrometry using (18)O-labeled internal standards

    Mirgorodskaya, O A; Kozmin, Y P; Titov, M I;

    2000-01-01

    A method for quantitating proteins and peptides in the low picomole and sub-picomole range has been developed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with internal (18)O-labeled standards. A simple procedure is proposed to produce such internal standards for...

  15. Can tree-ring isotopes (δ18O and δ13C) improve our understanding of hydroclimate variability in the Columbia River Basin?

    Csank, A. Z.; Wise, E.; McAfee, S. A.

    2015-12-01

    The trajectory of incoming storms from the Pacific Ocean has a strong impact on hydroclimate in the Pacific Northwest. Shifts between zonal and meridional flow are a key influence on drought and pluvial regimes in both the PNW and the western United States as a whole. Circulation-dependent variability in the isotopic composition of precipitation can be recorded and potentially reconstructed using δ18O records derived from tree-rings. Here we present isotopic records of δ18O and δ13C from ponderosa pine (Pinus ponderosa) for the period 1950-2013 from six sites located in the lee of the Cascades in eastern Washington. Because of the orientation of the Cascades, zonal flow will result in an intensified rain shadow whereas meridional flow allows moisture to penetrate at a lower elevation leading to a lower rainout effect. This means zonal flow results in drier conditions in eastern Washington and the converse for meridional flow. We hypothesized that more depleted precipitation δ18O values will occur with periods of more zonal flow across the PNW and will be recorded by trees at our sites. Results show a strong relationship between our δ18O chronologies and winter precipitation (R = -0.50; p<0.001). δ13C chronologies from the same trees showed a relationship to prior fall/winter (pOct-pDec) precipitation (R = -0.46; p<0.005) suggesting a possible link to antecedent moisture conditions. With a focus on years with clear zonal and meridional flow regimes, we regressed the tree-ring δ18O anomaly against the instrumental record of total precipitation and compared the residual series to records of storm track for the period 1978-2008, and we found a detectable signal where the most depleted δ18O was generally associated with zonal flow and the most enriched δ18O with meridional flow. However, there are still some years where the relationship is unclear. Further work is aimed at understanding these anomalous years and extending our record beyond the instrumental

  16. Reconciling single chamber Mg/Ca with whole test δ18O in surface to deep dwelling planktonic foraminifera from the Mozambique Channel

    J. Steinhardt

    2014-12-01

    Full Text Available Most planktonic foraminifera migrate vertically through the water column during life, meeting a range of depth-related conditions as they grow and calcify. For reconstructing past ocean conditions from geochemical signals recorded in their shells it is therefore necessary to know vertical habitat preferences. Species with a shallow habitat and limited vertical migration will reflect conditions of the surface mixed layer and short- and meso-scale (i.e. seasonal perturbations therein. Species spanning a wider range of depth habitats, however, will contain a more heterogeneous, intra-specimen variability (i.g. Mg/Ca and δ18O, which is less for species calcifying below the seasonal mixed layer (SML. Here we present results on single-chamber Mg/Ca combined with single shell δ18O and δ13C of surface water Globigerinoides ruber, the thermocline-dwelling Neogloboquadrina dutertrei and Pulleniatina obliquiloculata and the deep dweller Globorotalia scitula from the Mozambique Channel. Species-specific Mg/Ca, δ13C and δ18O data combined with a depth-resolved mass balance model confirm distinctive migration and calcification patterns for each species as a function of hydrography. Whereas single specimen δ18O not always reveal changes in depth habitat related to hydrography (i.g. temperature, measured Mg/Ca of the last chambers can only be explained by active migration in response to changes in temperature stratification. Since species show different responses to changes in hydrography, their shell chemistry can be used to reconstruct different components of the past ocean climate system such as seasonality and depth stratification. Here we present combined single-specimen δ18O and single-chamber Mg/Ca measurements for different species, providing a composite of thermocline and sub-thermocline conditions. These results allow for species-specific reconstruction of calcification depths, using a mass balance model, of four species of planktonic

  17. Maintaining consistent traceability in high-precision isotope measurements of CO2: a way to verify atmospheric trends of δ13C and δ18O

    L. Huang

    2013-07-01

    Full Text Available Maintaining consistent traceability of high-precision measurements of CO2 isotopes is critical in order to obtain accurate atmospheric trends of δ13C and δ18O (in CO2. Although a number of laboratories/organizations around the world have been conducting baseline measurements of atmospheric CO2 isotopes for several decades, reports on the traceability and maintenance are rare. In this paper, a principle and an approach for maintaining consistent traceability in high-precision isotope measurements (δ13C and δ18O of atmospheric CO2 are described. The concept of Big Delta is introduced and its role in maintaining traceability of the isotope measurements is described and discussed extensively. The uncertainties of the traceability have been estimated based on annual calibration records over the last 10 yr. The overall uncertainties of CO2 isotope measurements for individual ambient samples analyzed by the program at Environment Canada have been estimated (excluding these associated with the sampling. The values are 0.02 and 0.05‰ in δ13C and δ18O, respectively, which are close to the World Meteorological Organization (WMO targets for data compatibility. The annual rates of change in δ13C and δ18O of the primary anchor (which links the flask measurements back to the VPDB-CO2 scale are close to zero (−0.0016 ± 0.0012‰, and −0.006 ± 0.003‰ per year, respectively over a period of 10 yr (2001–2011. The average annual changes of δ13C and δ18O in air CO2 at Alert GAW station over the period from 1999 to 2010 have been evaluated and confirmed; they are −0.025 ± 0.003‰ and 0.000 ± 0.010‰, respectively. The results are consistent with a continuous contribution of fossil fuel CO2 to the atmosphere, having a trend toward more negative in δ13C, whereas the lack of change in δ18O likely reflects the influence from the global hydrologic cycle. The total change of δ13C and δ18O during this period is ~0.27‰ and ~0.00

  18. Temporal and spatial variations of δ15N and δ18O for atmospheric N2O above the oceanic surface from Shanghai to Antarctica

    2008-01-01

    During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concen-tration (PreCon) of trace gases. The temporal and spatial variations of δ 15N and δ 18O in atmospheric N2O were analyzed. The mean δ 15N and δ 18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ 15N (6.05‰―7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ 18O (43.05‰―48.78‰) showed a large fluctua-tion. The δ 15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ 18O. The summertime variations of δ 15N and δ 18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ 15N and δ 18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ 15N and δ 18O values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets.

  19. Archaean fluid-assisted crustal cannibalism recorded by low δ18O and negative ɛHf(T) isotopic signatures of West Greenland granite zircon

    Hiess, Joe; Bennett, Vickie C.; Nutman, Allen P.; Williams, Ian S.

    2011-06-01

    The role of fluids during Archaean intra-crustal magmatism has been investigated via integrated SHRIMP U-Pb, δ18O and LA-MC-ICPMS 176Hf isotopic zircon analysis. Six rock samples studied are all from the Nuuk region (southern West Greenland) including two ~3.69 Ga granitic and trondhjemitic gneisses, a 3.64 Ga granitic augen gneiss, a 2.82 Ga granodioritic Ikkattoq gneiss, a migmatite with late Neoarchaean neosome and a homogeneous granite of the 2.56 Ga Qôrqut Granite Complex (QGC). All zircon grains were thoroughly imaged to facilitate analysis of magmatic growth domains. Within the zircon analysed, there is no evidence for metamictization. Initial ɛHf zircon values ( n = 63) are largely sub-chondritic, indicating the granitic host magmas were generated by the remelting of older, un-radiogenic crustal components. Zircon from some granite samples displays more than one 207Pb/206Pb age, and correlated with 176Hf/177Hf compositions can trace multiple phases of remelting or recrystallization during the Archaean. Model ages calculated using Lu/Hf arrays for each sample indicate that the crustal parental rocks to the granites, granodiorites and trondhjemites segregated from a chondrite-like reservoir at an earlier time during the Archaean, corresponding to known formation periods of more primitive tonalite-trondhjemite-granodiorite (TTG) gneisses. Zircon from the ~3.69 Ga granite, the migmatite and QGC granite contains Eoarchaean cores with chondritic 176Hf/177Hf and mantle-like δ18O compositions. The age and geochemical signatures from these inherited components are identical to those of surrounding tonalitic gneisses, further suggesting genesis of these granites by remelting of broadly tonalitic protoliths. Zircon oxygen isotopic compositions ( n = 62) over nine age populations (six igneous and three inherited) have weighted mean or mean δ18O values ranging from 5.8 ± 0.6 to 3.7 ± 0.5‰. The 3.64 Ga granitic augen gneiss sample displays the highest δ18O with

  20. Mesures conjointes des rapports Sr/Ca et δ 18O effectuées sur Acropora nobilis et Pontes lutea: le paléothermomètre Sr/Ca est-il toujours fiable?

    Boiseau, Muriel; Cornu, Hélène; Turpin, Laurent; Juillet-Leclerc, Anne

    1997-11-01

    We measured the Sr/Ca and 18O/ 16O ratios in Acropora nobilis and Porites lutea, from the Mayotte lagoon. As the variations of δ 18O seawater are negligible, coral δ 18O aragonite reflects only seasonal temperature variations. While there is a good agreement between the Sr/Ca ratio and δ 18O for Acropora nobilis, it is not the case for Porites lutea. Coral biological and environmental parameters cannot explain the discrepancies between Sr/Ca ratios and isotopic measurements. However, transport mechanisms of Sr 2+ and Ca 2+ and the presence of two mineralogical structures of strontium may affect the Sr/Ca ratio.

  1. An oxygen isotope profile in a section of Cretaceous oceanic crust, Samail Ophiolite, Oman: Evidence for δ^(18)O buffering of the oceans by deep (>5 km) seawater-hydrothermal circulation at mid-ocean ridges

    Gregory, Robert T.; Taylor, Hugh P., Jr.

    1981-01-01

    Isotopic analyses of 75 samples from the Samail ophiolite indicate that pervasive subsolidus hydrothermal exchange with seawater occurred throughout the upper 75% of this 8-km-thick oceanic crustal section; locally, the H_2O even penetrated down into the tectonized peridotite. Pillow lavas (δ^(18)O = 10.7 to 12.7) and sheeted dikes (4.9 to 11.3) are typically enriched in ^(18)O, and the gabbros (3.7 to 5.9) are depleted in ^(18)O. In the latter rocks, water/rock ≤ 0.3, and δ^(18)O_(cpx) ≈ 2.9...

  2. Isotopic variations (δ13 C and δ18 O) in Siderastrea stellata (Cnidaria-Anthozoa), Itamaraca island, State of Pernambuco, Northeastern Brazil

    Isotopic determinations for O and C were performed in coral skeletons collected in beach rocks from two localities (Orange and Catuama), Itamaraca Island, north littoral of the State of pernambuco, northeastern Brazil. Large variations of δ18 O and δ13 C in corals from both localities are found, the largest ones being observed at the Orange locality δ13 C in this locality varies from -0.8 to +1.8% PDB and δ1.8 O from -5.3 to -1.8% PDB, while at the Catuama locality, they vary from -1.8 to 0.1% PDB and -3.8 to -2.7% PDB, respectively. Large variations in δ18 O (up to 2.5%) coupled with weakly defined positive correlation between δ18 O and δ13 C, can be attributed to temperature variations as consequence of climatic perturbations. Temperature estimates, calculated from δ18 O values, assuming isotopic equilibrium with seawater, yield values between 24.9 deg C and 43.1 deg C at Orange, and from 28.4 deg C to 35 deg C at Catuama, all of them (expect one growth band from one sample) are high enough for the full development of the coral colony. Temperature average is 31.4 deg C at Orange, which is a little bit higher than that at Catuama, but both of them indicate thermal stress conditions. In all analyzed specimens, expect for one, at Orange, T increases was accompanied by decreasing in the organic activity, as suggested by corresponding negative δ13 C anomaly. Therefore, the observed bleaching is possibly related to thermal stress and the high T may be related to the El Nino-Southern Oscillation (ENSO) warning event. On the other hand, anthropogenic action at Orange, local of intense tourism throughout the year, coupled with high rate of sedimentation in the region, may contribute to the observed coral bleaching. (author)

  3. Prediction of plant vulnerability to salinity increase in a coastal ecosystem by stable isotopic composition (δ18O) of plant stem water: a model study

    Zhai, Lu; Jiang, Jiang; DeAngelis, Don; Sternberg, Leonel d.S.L

    2016-01-01

    Sea level rise and the subsequent intrusion of saline seawater can result in an increase in soil salinity, and potentially cause coastal salinity-intolerant vegetation (for example, hardwood hammocks or pines) to be replaced by salinity-tolerant vegetation (for example, mangroves or salt marshes). Although the vegetation shifts can be easily monitored by satellite imagery, it is hard to predict a particular area or even a particular tree that is vulnerable to such a shift. To find an appropriate indicator for the potential vegetation shift, we incorporated stable isotope 18O abundance as a tracer in various hydrologic components (for example, vadose zone, water table) in a previously published model describing ecosystem shifts between hammock and mangrove communities in southern Florida. Our simulations showed that (1) there was a linear relationship between salinity and the δ18O value in the water table, whereas this relationship was curvilinear in the vadose zone; (2) hammock trees with higher probability of being replaced by mangroves had higher δ18O values of plant stem water, and this difference could be detected 2 years before the trees reached a tipping point, beyond which future replacement became certain; and (3) individuals that were eventually replaced by mangroves from the hammock tree population with a 50% replacement probability had higher stem water δ18O values 3 years before their replacement became certain compared to those from the same population which were not replaced. Overall, these simulation results suggest that it is promising to track the yearly δ18O values of plant stem water in hammock forests to predict impending salinity stress and mortality.

  4. Synthesis of porous LiFe0.2Mn1.8O4 with high performance for lithium-ion battery

    Highlights: • Porous LiFe0.2Mn1.8O4 was fabricated with P123 as a template through a nitrate decomposition method • A high rate capacity and cycling stability were demonstrated when used as cathode in LIBs • This strategy is expected to fabricate other multiple metal oxides with porous structures - Abstract: A facile and effective route was developed for the fabrication of LiFe0.2Mn1.8O4 with porous structures by using Pluronic P-123 as a soft template, based on a nitrate decomposition method. The resultant LiFe0.2Mn1.8O4 was characterized by XRD, SEM, as well as N2 adsorption/desorption measurements which showed a porous structure with a pore size centered at 20 nm. When used as cathode materials in lithium battery, the as-synthesized LiFe0.2Mn1.8O4 exhibited a discharge capacity of 122 mAh g−1 at 1 C and 102 mAh g−1 at 5 C. Moreover, after 500 cycles, the capacity retention (108 mAh g−1) reached 88% of the initial capacity at 1 C. As compared with conventional cathode LiMn2O4, the high performance is believed to originate from the combined effects of porous structure, iron doping and highly crystalline nature of the obtained LiFe0.2Mn1.8O4. This strategy is expected to allow the fabrication of other multiple metal oxides with porous structures for high performance cathode materials

  5. Rock Deformation, Component Migration and 18O/16O Variations during Mylonitization in the Southern Tan-Lu Fault Belt

    YANG Xiaoyong; LIU Deliang; FENG Min; YU Qingni; WANG Kuiren

    2007-01-01

    This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids flowing through the shear zone during mylonitization, accompanied with the loss of volume of rocks and variations of elements and oxygen isotopes. The calculated temperature for mylonitization in different mylonites ranges from 446 to 484℃, corresponding to that of 475 to 500℃for the wall rocks. The condition of differential stress during mylonization has been obtained between 99 and 210 MPa, whereas the differential stress in the wall rock gneiss is 70-78 MPa. The mylonites are enriched by factors of 1.32-1.87 in elements such as TiO2, P2O5, MnO, Y, Zr and V and depleted in SiO2, Na2O, K2O, Al2O3, Sr, Rb and light REEs compared to their protolith gneiss. The immobile element enrichments are attributed to enrichments in residual phases such as ilmentite, zircon, apatite and epidote in mylonites and are interpreted as due to volume losses from 15% to 60% in the ductile shear zone. The largest amount of SiO2 loss is 35.76 g/100 g in the ductile shear zone, which shows the fluid infiltration. Modeling calculated results of the fluid/rock ratio for the ductile shear zone range from 196 to 1192 by assuming different degrees of fluid saturation. Oxygen isotope changes of quartz and feldspar and the calculated fluid are corresponding to the variations of differential flow stress in the ductile shear zone. With increasing differential flow stress, the mylonites show a slight decrease of δ18O in quartz, K-feldspar and fluid.

  6. The influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exhanges

    Still, C.J.; Riley, W.J.; Biraud, S.C.; Noone, D.C.; Buenning, N.H.; Randerson, J.T.; Torn, M.S.; Welker, J.; White, J.W.C.; Vachon, R.; Farquhar, G.D.; Berry, J.A.

    2009-05-01

    This study evaluates the potential impact of clouds on ecosystem CO{sub 2} and CO{sub 2} isotope fluxes ('isofluxes') in two contrasting ecosystems (a broadleaf deciduous forest and a C{sub 4} grassland), in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model, ISOLSM. Our model results indicate a large impact of clouds on ecosystem CO{sub 2} fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day. This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C{sub 4} grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean {delta}{sup 18}O of CO{sub 2} may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.

  7. Energy loss straggling data of 28Si, 27Al, 24Mg, 19F, 16O, and 12C heavy ions in thin polymeric Formvar foil over a range of energies 0.1–0.6 MeV/u by time-of-flight spectrometry

    The energy-loss straggling of 28Si, 27Al, 24Mg, 19F, 16O and 12C partially stripped heavy ions has been determined in Formvar polymeric thin foil over a continuous range of energies 0.1–0.6 MeV/u, by using a powerful method based on the combination of Heavy Ion-Elastic Recoil Detection Analysis (HI-ERDA) technique and Time of Flight (ToF) spectrometer. The obtained energy loss straggling values have been analyzed and compared with the corresponding computed values adopting some widely used energy loss straggling formulations such as, Bohr, Bethe–Livingston and Yang formulas. The aim of such a comparison is to check the reliability and accuracy of the existing energy loss straggling formulations. The experimental results of energy loss straggling of all ions are found to be significantly greater than those predicted by the theories. These differences can be attributed to the charge exchange straggling. This effect has to be taken into account in order to explain the obtained results. - Highlights: • Measurement of energy loss straggling data of 28Si, 27Al, 24Mg, 19F, 16O, and 12C heavy ions in thin polymeric Formvar foil. • The heavy ion elastic recoil detection analysis (HIERDA) technique coupled with time of flight (ToF) spectrometer was used. • The aim of such a study is to check the reliability and accuracy of the existing energy loss straggling formulations

  8. Impact of Bolivian paleolake evaporation on the δ18O of the Andean glaciers during the last deglaciation (18.5-11.7 ka): diatom-inferred δ18O values and hydro-isotopic modeling

    Quesada, Benjamin; Sylvestre, Florence; Vimeux, Françoise; Black, Jessica; Paillès, Christine; Sonzogni, Corinne; Alexandre, Anne; Blard, Pierre-Henri; Tonetto, Alain; Mazur, Jean-Charles; Bruneton, Hélène

    2015-07-01

    During the last deglaciation, the Bolivian Altiplano (15-23°S, 66-70°W) was occupied by paleolake Tauca covering, at least, ˜51,000 km2 at its maximum highstand between 16.5 and 15 ka. Twenty-five hundred years later, after a massive regression, a new transgressive phase, produced paleolake Coipasa, smaller than Tauca and restricted to the southern part of the basin. These paleolakes were overlooked at the west by the Sajama ice cap. The latter provides a continuous record of the oxygen isotopic composition of paleo-precipitation for the last 25 ka. Contemporaneously to the end of paleolake Tauca, around 14.3 ka, the Sajama ice cap recorded a significant increase in ice oxygen isotopic composition (δ18Oice). This paper examines to what extent the disappearance of Lake Tauca contributed to precipitation on the Sajama summit and this specific isotopic variation. The water δ18O values of paleolakes Tauca and Coipasa (δ18Olake) were quantitatively reconstructed from 18.5 to 11.7 ka based on diatom isotopic composition (δ18Odiatoms) and ostracod isotopic composition (δ18Ocarbonates) retrieved in lacustrine sediments. At a centennial time scale, a strong trend appears: abrupt decreases of δ18Olake during lake fillings are immediately followed by abrupt increases of δ18Olake during lake level stable phases. The highest variation occurred at ˜15.8 ka with a δ18Olake decrease of about ˜10‰, concomitant with the Lake Tauca highstand, followed ˜400 years later by a 7‰ increase in δ18Olake. A simple hydro-isotopic modeling approach reproduces consistently this rapid "decrease-increase" feature. Moreover, it suggests that this unexpected re-increase in δ18Olake after filling phases can be partly explained by an equilibration of isotopic fluxes during the lake steady-state. Based on isotopic calculations during lake evaporation and a simple water stable isotopes balance between potential moisture sources at Sajama (advection versus lake evaporation), we show

  9. Identification and correction of spectral contamination in 2H/1H and 18O/16O measured in leaf, stem, and soil water.

    Schultz, Natalie M; Griffis, Timothy J; Lee, Xuhui; Baker, John M

    2011-11-15

    Plant water extracts typically contain organic materials that may cause spectral interference when using isotope ratio infrared spectroscopy (IRIS), resulting in errors in the measured isotope ratios. Manufacturers of IRIS instruments have developed post-processing software to identify the degree of contamination in water samples, and potentially correct the isotope ratios of water with known contaminants. Here, the correction method proposed by an IRIS manufacturer, Los Gatos Research, Inc., was employed and the results were compared with those obtained from isotope ratio mass spectrometry (IRMS). Deionized water was spiked with methanol and ethanol to create correction curves for δ(18)O and δ(2)H. The contamination effects of different sample types (leaf, stem, soil) and different species from agricultural fields, grasslands, and forests were compared. The average corrections in leaf samples ranged from 0.35 to 15.73‰ for δ(2)H and 0.28 to 9.27‰ for δ(18)O. The average corrections in stem samples ranged from 1.17 to 13.70‰ for δ(2)H and 0.47 to 7.97‰ for δ(18)O. There was no contamination observed in soil water. Cleaning plant samples with activated charcoal had minimal effects on the degree of spectral contamination, reducing the corrections, by on average, 0.44‰ for δ(2)H and 0.25‰ for δ(18)O. The correction method eliminated the discrepancies between IRMS and IRIS for δ(18)O, and greatly reduced the discrepancies for δ(2)H. The mean differences in isotope ratios between IRMS and the corrected IRIS method were 0.18‰ for δ(18)O, and -3.39‰ for δ(2)H. The inability to create an ethanol correction curve for δ(2)H probably caused the larger discrepancies. We conclude that ethanol and methanol are the primary compounds causing interference in IRIS analyzers, and that each individual analyzer will probably require customized correction curves. PMID:22006400

  10. Temporal and spatial variations of δ15N and δ18O for atmospheric N2O above the oceanic surface from Shanghai to Antarctica

    ZHU RenBin; LIU YaShu; XU Hua; MA Jing; SUN LiGuang

    2008-01-01

    During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concen-tration (PreCon) of trace gases. The temporal and spatial variations of δ15N and δ18O in atmospheric N2O were analyzed. The mean δ15N and δ18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ15N (6.05%o-7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ18o (43.05‰-48.78‰) showed a large fluctua-tion. The δ15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ18O. The summertime variations of δ15N and δ18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ15N and δ18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ15N and δ180 values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets.

  11. D- 18O enriched waters of the Coast Range Mountains, northern California: Connate and ore-forming fluids

    Peters, E. Kirsten

    1993-03-01

    D and 18O enriched waters of several weight percent salinity issue from hot and cold springs in Franciscan Complex and Great Valley Sequence rocks in the northern Coast Range Mountains of California. Although these waters have been described separately in the past and called "metamorphic," "connate," and "serpentinizing fluids," this study shows that the hot and cold springs are all fed by one source of water—trapped Cretaceous seawater modified by a variety of reactions. The district is an example of the complexities of subsurface waters and their importance for our understanding of metamorphic fluid sources, oil-field waters, and ore transport problems. The subsurface waters have a range of δ 34S values, including some near marine sulfate values (+20%.), and δ 13C near marine calcite values (0%.). Strontium isotopic signatures in the spring waters are derived from the Great Valley Sequence ( 87Sr /86Sr values near 0.705). The most saline spring pool is lined with serpentine phases found together as a fine white precipitate and has a pH of 11. One portion of the subsurface water is heated and reduced; it transports Au, Ag, Sb, As, and Hg to the surface (gold grades of the hot spring precipitates range from less than 1 ppm to over 10 ppm). These heated waters are chemically and isotopically similar to the fluids which formed Au mineralization at the nearby McLaughlin gold mine. The hot springs precipitate pyrite and native sulfur and are supersaturated with respect to calcite. Other springs are less saline and are oxidized, cooler, and diluted versions of the hot spring fluid. They do not carry ore metals but they are supersaturated with respect to silica and calcite. 3He /4He ratios of the springs gases are all above atmospheric values and indicate a possible magmatic component, consistent with the presence of Quaternary Clear Lake Volcanics. 129I data yield a minimum age of 60-80 Ma for the source of the iodide in the waters, consistent with the connate

  12. Oscillator Strengths and Predissociation Rates for W-X Bands and the 4P5P Complex in 13C18O

    Eidelsberg, Michele; Lemaire, Jean Louis; Federman, Steven; Stark, Glenn; Heays, Alan; Gavilan, Lisseth; Lyons, James R.; Smith, Peter L.; de Oliveira, Nelson; Joyeux, Denis

    2015-06-01

    In our ongoing experiments on the DESIRS beam-line at the SOLEIL Synchrotron, we are acquiring the necessary data on oscillator strengths and predissociation rates for modeling CO photochemistry in astronomical environments. A VUV Fourier Transform Spectrometer with a resolving power of about 350,000 allows us to discern individual lines in electronic transitions. Here we focus on results obtained from absorption spectra of 13C18O, for the W ^1Π - X ^1σ^+ bands with v'=0, 2, {and} 3 and v''=0 and three resolved bands involving transitions to the upper levels 4pπ(2), 5pπ(0), and 5pσ(0) of the 4p(2) and 5p(0) complexes. We compare our results with earlier determinations for this isotopologue of CO, as well as with our SOLEIL measurements on 12C16O, 13C16O, and 12C18O.

  13. Relationship between isotopic composition (Δ18O and Δ13C and plaktonic foraminifera test size in core tops from the Brazilian Continental Margin

    Paula Franco-Fraguas

    2011-12-01

    Full Text Available Stable oxygen (δ18O and carbon (δ13C isotopic signature registered in fossil planktonic foraminifera tests are widely used to reconstruct ancient oceanographic conditions. Test size is a major source of stable isotope variability in planktonic foraminifera found in sediment samples and thus can compromise paleoceanographic interpretations. Test size/stable isotope (δ18O and δ13C relationships were evaluated in two planktonic foraminifer species (Globigerinoides ruber (white and Globorotalia truncatulinoides (right in two core tops from the Brazilian Continental Margin. δ18 Omeasurements were used to predict the depth of calcification of each test size fraction. δ13C offsets for each test size fraction were then estimated. No systematic δ18O changes with size were observed in G. ruber (white suggesting a similar calcification depth range (c.a. 100 m during ontogeny. For G. truncatulinoides (right δ18O values increased with size indicating ontogenetic migration along thermocline waters (250-400 m. δ13C measurements and δ13C offsets increased with size for both species reflecting well known physiological induced ontogenetic-related variability. In G. ruber (white the largest test size fractions (300µm and >355µm more closely reflect δ13C DIC indicating they are best suited for paleoceanographic studies.O tamanho de testa dos foraminíferos é uma importante fonte de variabilidade isotópica (δ18O e δ13C em amostras de sedimento marinho comprometendo as interpretações paloeceanograficas. No presente estudo, avaliou-se a relação entre o sinal isotópico medido em diferentes frações de tamanho de testa das espécies planctônicas, Globigerinoides ruber (branca e Globorotalia truncatulinoides (dextral em amostras de topo de dois testemunhos localizados na Margem Continental Brasileira. Os valores de δ18O foram utilizados para estimar a profundidade de calcificação de cada fração de tamanho. Os desequilíbrios nos valores de

  14. Eocene-Oligocene proto-Cascades topography revealed by clumped (Δ47) and oxygen isotope (δ18O) geochemistry (Chumstick Basin, WA, USA)

    Methner, Katharina; Fiebig, Jens; Wacker, Ulrike; Umhoefer, Paul; Chamberlain, C. Page; Mulch, Andreas

    2016-03-01

    The topography of the present-day Washington Cascades impacts atmospheric circulation and precipitation patterns in the Pacific Northwest, introducing a pronounced orographic rain shadow in the lee of the mountain range. The temporal development of Cascade topography, however, remains largely unconstrained for the early Cenozoic. Based on coupled carbonate clumped isotope (Δ47) and oxygen isotope (δ18O) measurements we reconstruct δ18O values of Eocene groundwater (δ18Owater) in the Chumstick basin (central Washington), today located in the Cascade rain shadow. Δ47 (paleo)thermometry indicates a systematic change in basin burial temperatures from 110°C to 70°C depending on burial depth in the basin. These data are in good agreement with low-T thermochronological and vitrinite reflectance data, and further constrain the basin burial and exhumation history. In concert with field observations, microstructural analysis, and δ18O values of the analyzed carbonates, we suggest that the Δ47 temperatures and δ18O values reflect open-system carbonate cement recrystallization in meteoric-derived groundwaters during early burial diagenesis. Assuming open-system behavior, reconstructed mean δ18Owater values of ~ -7‰ (middle Eocene) to -9‰ (late Eocene/early Oligocene) are consistent with a low-elevation origin of the corresponding meteoric waters that permeated the sandstone/conglomerate members of the Eocene sedimentary units. In light of the paleogeographic setting of the Chumstick basin, the reconstructed δ18Owater values agree well with Pacific-derived moisture that did not experience strong rainout. The absence of a rain shadow effect therefore permits only moderate Eocene/Oligocene elevations at least for the southern part of the Washington proto-Cascades.

  15. Volcano Pectusan: composition of rocks, chronology of eruption (K-Ar) and evolution (87Sr/86Sr and δ18O)

    Paper presents the results of the isotope study of the Pectusan volcano northeast and western slopes located at the North Korea and China boundary. Fresh data on the K-Ar-isotope geochronology, on the rock mass composition enabled to trace the stages and the cycles in the evolution of the mentioned volcano. On the basis of the isotope study (87Sr/86Sr and δ18O) data one analyzed some problems dealing with the genesis of the alkali-sialic rocks

  16. Glycolate metabolism in low and high CO2-grown chlorella pyrenoidosa and Pavlova lutheri as determined by 18O-labeling

    Photorespiration in Chlorella pyrenoidosa Chick. was assayed by measuring 18O-labeled intermediates of the glycolate pathway. Glycolate, glycine, serine, and excreted glycolate were isolated and analyzed on a gas chromatograph/mass spectrometer to determine isotopic enrichment. Rates of glycolate synthesis were determined from 18O-labeling kinetics of the intermediates, pool sizes, derived rate equations, and nonlinear regression techniques. Glycolate synthesis was higher in high CO2-grown cells than in air-grown cells when both were assayed under the same O2 and CO2 concentrations. Synthesis of glycolate, for both types of cells, was stimulated by high O2 levels and inhibited by high CO2 levels. Glycolate synthesis in 1.5% CO2-grown Chlorella, when exposed to a 0.035% CO2 atmosphere, increased from about 41 to 86 nanomoles per milligram chlorophyll per minute when the O2 concentration was increased from 21 to 40%. Glycolate synthesis in air-grown cells increased from 2 to 6 nanomoles per milligram chlorophyll per minute under the same gas levels. Synthesis was undetectable when either the O2 concentration was lowered to 2% or the CO2-concentration was raised to 1.5%. Glycolate excretion was also sensitive to O2 and CO2 concentrations in 1.5% CO2-grown cells and the glycolate that was excreted was 18O-labeled. Air-grown cells did not excrete glycolate under any experimental condition. Indirect evidence indicated that glycolate may be excreted as a lactone in Chlorella. Photorespiratory 18O-labeling kinetics were determined for Pavlova lutheri, which unlike Chlorella and higher plants did not directly synthesize glycine and serine from glycolate. This alga did excrete a significant proportion of newly synthesized glycolate into the media

  17. Glycolate metabolism in low and high CO sub 2 -grown chlorella pyrenoidosa and Pavlova lutheri as determined by sup 18 O-labeling

    de Veau, E.J.; Burris, J.E. (Pennsylvania State Univ., University Park (USA))

    1989-11-01

    Photorespiration in Chlorella pyrenoidosa Chick. was assayed by measuring {sup 18}O-labeled intermediates of the glycolate pathway. Glycolate, glycine, serine, and excreted glycolate were isolated and analyzed on a gas chromatograph/mass spectrometer to determine isotopic enrichment. Rates of glycolate synthesis were determined from {sup 18}O-labeling kinetics of the intermediates, pool sizes, derived rate equations, and nonlinear regression techniques. Glycolate synthesis was higher in high CO{sub 2}-grown cells than in air-grown cells when both were assayed under the same O{sub 2} and CO{sub 2} concentrations. Synthesis of glycolate, for both types of cells, was stimulated by high O{sub 2} levels and inhibited by high CO{sub 2} levels. Glycolate synthesis in 1.5% CO{sub 2}-grown Chlorella, when exposed to a 0.035% CO{sub 2} atmosphere, increased from about 41 to 86 nanomoles per milligram chlorophyll per minute when the O{sub 2} concentration was increased from 21 to 40%. Glycolate synthesis in air-grown cells increased from 2 to 6 nanomoles per milligram chlorophyll per minute under the same gas levels. Synthesis was undetectable when either the O{sub 2} concentration was lowered to 2% or the CO{sub 2}-concentration was raised to 1.5%. Glycolate excretion was also sensitive to O{sub 2} and CO{sub 2} concentrations in 1.5% CO{sub 2}-grown cells and the glycolate that was excreted was {sup 18}O-labeled. Air-grown cells did not excrete glycolate under any experimental condition. Indirect evidence indicated that glycolate may be excreted as a lactone in Chlorella. Photorespiratory {sup 18}O-labeling kinetics were determined for Pavlova lutheri, which unlike Chlorella and higher plants did not directly synthesize glycine and serine from glycolate. This alga did excrete a significant proportion of newly synthesized glycolate into the media.

  18. Accurate experimental determination of the isotope effects on the triple point temperature of water. II. Combined dependence on the 18O and 17O abundances

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

    2015-12-01

    This paper is the second of two articles on the quantification of isotope effects on the triple point temperature of water. In this second article, we address the combined effects of 18O and 17O isotopes. We manufactured five triple point cells with waters with 18O and 17O abundances exceeding widely the natural abundance range while maintaining their natural 18O/17O relationship. The 2H isotopic abundance was kept close to that of VSMOW (Vienna Standard Mean Ocean Water). These cells realized triple point temperatures ranging between  -220 μK to 1420 μK with respect to the temperature realized by a triple point cell filled with VSMOW. Our experiment allowed us to determine an accurate and reliable value for the newly defined combined 18, 17O correction parameter of AO  =  630 μK with a combined uncertainty of 10 μK. To apply this correction, only the 18O abundance of the TPW needs to be known (and the water needs to be of natural origin). Using the results of our two articles, we recommend a correction equation along with the coefficient values for isotopic compositions differing from that of VSMOW and compare the effect of this new equation on a number of triple point cells from the literature and from our own institute. Using our correction equation, the uncertainty in the isotope correction for triple point cell waters used around the world will be  <1 μK.

  19. Study of Leachate Contamination in Bantar Gebang Landfill to Its Shallow Groundwater using Natural Isotope Tracers of 18O, 2H and 3H

    E.R. Pujiindiyati; P. Sidauruk

    2015-01-01

    Leaching from Bantar Gebang landfill, Jakarta’s main municipal landfill, especially from its two waste water treatment plants (plant A in zone-3 and plant B in Sumur Batu) to underlying aquifer has been studied using isotope techniques. The study was based on the abundances of the heavier isotopes in water molocules namely 18O, 2H (deuterium) and 3H (tritium). Because both water in the waste-water treatment plants and groundwater have undergone different independent physical processes, it was...

  20. The effects of assimilation of country rocks by magmas on 18O/16O and 87Sr/86Sr systematics in igneous rocks

    Examples of positive correlations between intial 87Sr/86Sr and delta18O have now been shown to be very common in igneous rock series. These data in general require some type of mixing of mantle-derived igneous rocks with high-18O, high-87Sr crustal metamorphic rocks that once resided on or near the Earth's surface, such as sedimentary rocks or hydrothermally altered volcanic rocks. Mixing that involves assimilation of country rocks by magmas, however, is not a simple two-end-member process; heat balance requires appreaciable crystallization of cumulates. In such cases, the isotopic compositions may strongly reflect this open-system behavior and indicate the process of assimilation, whereas the major element chemical compositions of the contaminated magmas will be largely controlled by crystal-melt equilibria and crastallization paths fixed by multicomponent cotectics. A variety of oxygen and strontium isotope mixing curves were therefore calculated for this process of combined assimilation-fractional crystallization. The positions and characteristics of the resultant curves on delta18O-87Sr/86Sr diagrams markedly diverge from simple two end-member mixing relationships. Based on the above, model calculation can be crudely fitted to two igneous rock suites (Adamello and Roccamonfina in Italy), but the shapes of the calculated curves appear to rule out magmatic assimilation as an explanation for most delta18O-87Sr/86Sr correlations discovered so far, including all of those involving calc-alkaline granitic batholiths and andesitic volcanic rocks. The isotopic relationshipfs in such magma types must be inherited from their source regions, resumably reflecting patterns that existed in the parent rocks (or magmas) prior to or during melting. (orig.)

  1. Dense cores in dark clouds. 9: Observations of (13)CO and C(18)O in Vela, Chamaeleon, Musca, and the Coalsack

    Vilas-Boas, J. W. S.; Myers, P. C.; Fuller, G. A.

    1994-09-01

    One hundred one condensations with average optical size less than 7 min and visual extinction greater than 2.5 mag have been selected from European Southern Observatory (ESO) J plates, extinction maps, and catalogs of southern hemisphere dark clouds for observation in the (13)CO and C(18)O J = 1 goes to 0 transitions. These regions are condensations in the dark molecular clouds Musca, Coalsack, Chamaeleon II, Chamaeleon III, and cometary globules in Vela and Gum nebula. A search for IRAS point sorces having colors of young stellar objects shows that these condensations have at most seven associated young stellar objects-far fewer than in Taurus and Ophiuchus. These 101 condensations generally have lower (13)CO and C(18)O line intensity, C(18)O optical depth, and (13)CO line width than do 90 condensations in Taurus, Ophiuchus, and Cepheus. Similarly, 47 of these southern condensations having star-count estimates of visual extinction generally have less extinction than do the 19 condensations in Taurus having extinction estimated by the same method. The C(18)O to (13)CO line-width ratio for the cometary globules in the Vela ragion is greater than for the other clouds, indicating that the (13)CO line width observed toward dark cloud condensations is related to the more extended and less dense intercondensation gas. Radial velocities suggest that the system of Vela globules has velocity dispersion 4.7 km/s, which is at least 2 times greater than the dispersion determined from formalhyde observations. The Musca filament has velocities which are slightly higher-by approximately 0.5 km/s-in the center than at the ends of the filament. Chamaeleon III has a 0.2 km/s velocity gradient and Chamaeleon II has no indication of velocity gradients. The Chamaeleon clouds and the Musca filament appear close to virial equilibrium.

  2. Follow-up observations of Planck cold clumps in $^{12}$CO/$^{13}$CO/C$^{18}$O (1--0) transitions

    Wu, Yuefang; Meng, Fanyi

    2012-01-01

    The Planck Early Cold Cores Catalog (ECC) provides an unbiased list of Galactic cold clumps, which form an ideal sample for studying the early phases of star formation (\\cite[Planck Collabrators et al. 2011]{Planck_etal11}). To study their properties, we have carried out a molecular line ($^{12}$CO/$^{13}$CO/C$^{18}$O) survey towards 674 Planck cold clumps in the ECC with the PMO 13.7 m telescope.

  3. 18O isotope effect in 13C nuclear magnetic resonance spectroscopy. Part 9. Hydrolysis of benzyl phosphate by phosphatase enzymes and in acidic aqueous solutions

    The 18O isotope-induced shifts in 13C and 31P nuclear magnetic resonance (NMR) spectroscopy were used to establish the position of bond cleavage in the phosphatase-catalyzed and acid-catalyzed hydrolysis reactions of benzyl phosphate. The application of the 18O-isotope effect in NMR spectroscopy affords a continuous, nondestructive assay method for following the kinetics and position of bond cleavage in the hydrolytic process. The technique provides advantages over most discontinuous methods in which the reaction components must be isolated and converted to volatile derivatives prior to analysis. In the present study, [α-13C,ester-18O]benzyl phosphate and [ester-18O]benzyl phosphate were synthesized for use in enzymatic and nonenzymatic studies. Hydrolysis reactions catalyzed by the alkaline phosphatase from E. coli and by the acid phosphatases isolated from human prostate and human liver were all accompanied by cleavage of the substrate phosphorus-oxygen bond consistent with previously postulated mechanisms involving covalent phosphoenzyme intermediates. An extensive study of the acid-catalyzed hydrolysis of benzyl phosphate at 750C revealed that the site of bond cleavage is dependent on pH. At pH less than or equal to 1.3, the hydrolysis proceeds with C-O bond cleavage; at 1.3 2H]Benzyl phosphate was also synthesized. Hydrolysis of this chiral benzyl derivative demonstrated that the acid-catalyzed C-O bond scission of benzyl phosphate proceeds by an A-1 (S/sub N/1) mechanism with 70% racemization and 30% inversion at carbon. 37 references, 4 figures, 2 tables

  4. Variation of atmospheric CO, δ13C, and δ18O at high northern latitude during 2004-2009: Observations and model simulations

    Park, Keyhong; Wang, Zhihui; Emmons, Louisa K.; Mak, John E.

    2015-10-01

    Atmospheric CO mixing ratios and stable isotope ratios (δ13C and δ18O) were measured at a high northern latitude site (Westman Islands, Iceland) from January 2004 to March 2010 in order to investigate recent multiyear trends of the sources of atmospheric carbon monoxide in the extratropical Northern Hemisphere. During this period, we observed a decrease of about 2% per year in CO mixing ratios with little significant interannual variability. The seasonal cycles for δ13C and δ18O in CO are similar to that in the CO mixing ratio, and there is a pronounced interannual variation in their seasonal extremes occurring in summer and fall, which is driven by changes in the relative contribution of different sources. Some of the sources of CO are anthropogenic in character (e.g., fossil fuel and biofuel combustion and agricultural waste burning), and some are primarily natural (e.g., oxidation atmospheric methane and other hydrocarbons and wildfires), and distinction among the various major sources can, more or less, be distinguished by the stable isotopic composition of CO. We compare our observations with simulations from a 3-D global chemical transport model (MOZART-4, Model for Ozone and Related Chemical Tracers, version 4). Our results indicate the observed trend of anthropogenic CO emissions is mostly responsible for the observed variation in δ13C and δ18O of CO during 2004-2009. Especially, the δ18O enriched sources such as fossil fuel and biofuel sources are controlling the variation. The modeling results indicate decreasing trends in the fossil fuel and biofuel source contributions at Iceland of -0.61 ± 0.26 ppbv/yr and -0.38 ± 0.10 ppbv/yr, respectively, during the observation period.

  5. Analysis of stable isotope ratios (δ18O and δ2H) in precipitation of the Verde River watershed, Arizona 2013 through 2014

    Beisner, Kimberly R.; Paretti, Nicholas V.; Tucci, Rachel S.

    2016-01-01

    Stable isotope delta values (δ18O and δ2H) of precipitation can vary with elevation, and quantification of the precipitation elevation gradient can be used to predict recharge elevation within a watershed. Precipitation samples were analyzed for stable isotope delta values between 2003 and 2014 from the Verde River watershed of north-central Arizona. Results indicate a significant decrease in summer isotopic values overtime at 3,100-, 4,100-, 6,100-, 7,100-, and 8,100-feet elevation. The updated local meteoric water line for the area is δ2H = 7.11 δ18O + 3.40. Equations to predict stable isotopic values based on elevation were updated from previous publications in Blasch and others (2006), Blasch and Bryson (2007), and Bryson and others (2007). New equations were separated for samples from the Camp Verde to Flagstaff transect and the Prescott to Chino Valley transect. For the Camp Verde to Flagstaff transect, the new equations for winter precipitation are δ18O = -0.0004z − 8.87 and δ2H = -0.0029z − 59.8 (where z represents elevation in feet) and the summer precipitation equations were not statistically significant. For the Prescott to Chino Valley transect, the new equations for summer precipitation are δ18O = -0.0005z − 3.22 and δ2H = -0.0022z − 27.9; the winter precipitation equations were not statistically significant and, notably, stable isotope values were similar across all elevations. Interpretation of elevation of recharge contributing to surface and groundwaters in the Verde River watershed using the updated equations for the Camp Verde to Flagstaff transect will give lower elevation values compared with interpretations presented in the previous studies. For waters in the Prescott and Chino Valley area, more information is needed to understand local controls on stable isotope values related to elevation.

  6. A mechanistic model of H{sub 2}{sup 18}O and C{sup 18}OO fluxes between ecosystems and the atmosphere: Model description and sensitivity analyses

    Riley, W.J.; Still, C.J.; Torn, M.S.; Berry, J.A.

    2002-01-01

    The concentration of 18O in atmospheric CO2 and H2O is a potentially powerful tracer of ecosystem carbon and water fluxes. In this paper we describe the development of an isotope model (ISOLSM) that simulates the 18O content of canopy water vapor, leaf water, and vertically resolved soil water; leaf photosynthetic 18OC16O (hereafter C18OO) fluxes; CO2 oxygen isotope exchanges with soil and leaf water; soil CO2 and C18OO diffusive fluxes (including abiotic soil exchange); and ecosystem exchange of H218O and C18OO with the atmosphere. The isotope model is integrated into the land surface model LSM, but coupling with other models should be straightforward. We describe ISOLSM and apply it to evaluate (a) simplified methods of predicting the C18OO soil-surface flux; (b) the impacts on the C18OO soil-surface flux of the soil-gas diffusion coefficient formulation, soil CO2 source distribution, and rooting distribution; (c) the impacts on the C18OO fluxes of carbonic anhydrase (CA) activity in soil and leaves; and (d) the sensitivity of model predictions to the d18O value of atmospheric water vapor and CO2. Previously published simplified models are unable to capture the seasonal and diurnal variations in the C18OO soil-surface fluxes simulated by ISOLSM. Differences in the assumed soil CO2 production and rooting depth profiles, carbonic anhydrase activity in soil and leaves, and the d18O value of atmospheric water vapor have substantial impacts on the ecosystem CO2 flux isotopic composition. We conclude that accurate prediction of C18OO ecosystem fluxes requires careful representation of H218O and C18OO exchanges and transport in soils and plants.

  7. Unveiling stomata 24/7: can we use carbonyl sulfide (COS) and oxygen isotopes (18O) to constrain estimates of nocturnal transpiration across different evolutionary plant forms?

    Gimeno, Teresa E.; Ogee, Jerome; Bosc, Alexander; Genty, Bernard; Wohl, Steven; Wingate, Lisa

    2015-04-01

    Numerous studies have reported a continued flux of water through plants at night, suggesting that stomata are not fully closed. Growing evidence indicates that this nocturnal flux of transpiration might constitute an important fraction of total ecosystem water use in certain environments. However, because evaporative demand is usually low at night, nocturnal transpiration fluxes are generally an order of magnitude lower than rates measured during the day and perilously close to the measurement error of traditional gas-exchange porometers. Thus estimating rates of stomatal conductance in the dark (gnight) precisely poses a significant methodological challenge. As a result, we lack accurate field estimates of gnight and how it responds to different atmospheric drivers, indicating the need for a different measurement approach. In this presentation we propose a novel method to obtain detectable and robust estimates of gnight. We will demonstrate using mechanistic theory how independent tracers including the oxygen isotope composition of CO2 (δ18O) and carbonyl sulfide (COS) can be combined to obtain robust estimates of gnight. This is because COS and CO18O exchange within leaves are controlled by the light insensitive enzyme carbonic anhydrase. Thus, if plant stomata are open in the dark we will continue to observe COS and CO18O exchange. Using our theoretical model we will demonstrate that the exchange of these tracers can now be measured using advances in laser spectrometry techniques at a precision high enough to determine robust estimates of gnight. We will also present our novel experimental approach designed to measure simultaneously the exchange of CO18O and COS alongside the conventional technique that relies on measuring the total water flux from leaves in the dark. Using our theoretical approach we will additionally explore the feasibility of our proposed experimental design to detect variations in gnight during drought stress and across a variety of plant

  8. Seasonal incursion of Indian Monsoon humidity and precipitation into the southeastern Qinghai-Tibetan Plateau inferred from tree ring δ18O values with intra-seasonal resolution

    Zeng, Xiaomin; Liu, Xiaohong; Evans, Michael N.; Wang, Wenzhi; An, Wenling; Xu, Guobao; Wu, Guoju

    2016-06-01

    Incursion of the Indian Monsoon flow onto the Qinghai-Tibetan Plateau is an important regional moisture-delivery mechanism, but the causes of intra-seasonal and longer-term variations are poorly understood. We observed a clear intra-seasonal cycle in the oxygen isotope composition (δ18O) of Smith fir (Abies forrestii var. georgei) growing at two different altitudes (high-elevation site: 29°39‧N, 94°42‧E, 4200 m a.s.l.; low-elevation site: 29°39‧N, 94°43‧E, 3800 m a.s.l.) on a SE-facing slope in the Sygera Mountains, southeastern Qinghai-Tibetan Plateau. Mechanistic modeling suggests that δ18O of precipitation, which in turn depends on relative humidity and precipitation amount, is important in controlling the intra-seasonal tree-ring isotopic cycle, and we speculate that the same controls also operate on interannual and longer time scales. If so, multi-century δ18O records with intra-seasonal resolution may enable us to infer long-term variations in the incursion of the Indian Monsoon onto the Qinghai-Tibetan Plateau.

  9. Characterization of biodegradation intermediates of nonionic surfactants by MALDI-MS. 2. Oxidative biodegradation profiles of uniform octylphenol polyethoxylate in 18O-labeled water.

    Sato, Hiroaki; Shibata, Atsushi; Wang, Yang; Yoshikawa, Hiromichi; Tamura, Hiroto

    2003-01-01

    This paper reports the characterization of the biodegradation intermediates of octylphenol octaethoxylate (OP(8)EO) by means of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The biodegradation test study was carried out in a pure culture (Pseudomonas putida S-5) under aerobic conditions using OP(8)EO as the sole carbon source and (18)O-labeled water as an incubation medium. In the MALDI-MS spectra of biodegraded samples, a series of OP(n)EO molecules with n = 2-8 EO units and their corresponding carboxylic acid products (OP(n)EC) were observed. The use of purified OP(8)EO enabled one to distinguish the shortened OPEO molecules as biodegradation intermediates. Furthermore, the formation of OP(8)EC (the oxidized product of OP(8)EO) supported the notion that terminal oxidation is a step in the biodegradation process. When biodegradation study was carried out in (18)O-labeled water, incorporation of (18)O atoms into the carboxyl group was observed for OPEC, while no incorporation was observed for the shortened OPEO products. These results could provide some rationale to the biodegradation mechanism of alkylphenol polyethoxylates. PMID:12523845

  10. An automated technique for measuring deltaD and delta18O values of porewater by direct CO2 and H2 equilibration.

    Koehler, G; Wassenaar, L I; Hendry, M J

    2000-11-15

    The stable-oxygen and -hydrogen isotopic values (deltaD, delta18O) of porewater in geologic media are commonly determined on water obtained by extraction techniques such as centrifugation, mechanical squeezing, vacuum heating and cryogenic microdistillation, and azeotropic distillation. Each of these techniques may cause isotopic fractionation as part the extraction process and each is laborious. Here we demonstrate a new approach to obtain automated, high-precision deltaD and delta18O measurements of porewater in geologic sediments by direct H2- and CO2-porewater equilibration using a modified commercial CO2-water equilibrator. This technique provides an important and cost-effective improvement over current extraction methods, because many samples can be rapidly analyzed with minimal handling, thereby reducing errors and potential for isotopic fractionation. The precision and accuracy of direct H2- and CO2-porewater equilibration is comparable to or better than current porewater extraction methods. Finally, the direct equilibration technique allows investigators to obtain high-resolution (cm scale) porewater deltaD and delta18O profiles using cores from individual boreholes, eliminating the need for costly piezometers or conventional porewater extractions. PMID:11101245

  11. Determination Of Oxygen Isotope Ratio (18O-/16O) and Sulfur (34S-/32S) Value Of BaSO4 Din 5033 For Internal Standard

    It has been done an experiment to determine of oxygen(18O-/16O) and Sulfur (34S-/32S) ) isotop value of BaSO4 DIN 5033 (merck) for internal standard. The used technique for preparation of CO2 gas to measure oxygen isotop ratio ratio (stated as deltaδ 18O) is based on Rafter on Rafte method using graphite for reduction of BaSO4. Where the used technique for preparation of SO2 gas to measure isotope sulphur ratio (started as δ 34S) is based on Robinson - Kasakabe method using Cupro oxide to oxidize Ag2S. The result of this experiment is 11,48±0,41 0/00 and 5,00 plus minus ±0,33 o/oo for deltaδ 18O and δ 34S value respectively. Based on this experiment. BaSO4 DIN 5033 can be used as internal standard because is values both oxygen and sulphur lie in the middle of range of its variation in nature. The result of interlab comparison shows that the value of this experiment is nearly similar to the value obtained from laboratorium of Pinstech-Pakistan. To acquire the result, it is necessary to carry out more interlab comparison

  12. Applications of the 18O-isotope shift on 13C and 15N nuclear magnetic resonance spectroscopy to the study of bioorganic reaction mechanisms

    The study of reactions involving the formation and cleavage of carbon-oxygen or nitrogen-oxygen bonds has been significantly aided by recent demonstrations of the generality and characteristics of the 18O-isotope shift in 13C and 15N nuclear magnetic resonance spectroscopy. In many instances, the magnitudes of the 18O-induced isotopic shifts are sufficiently large as to permit the use of even modest NMR instrumentation and natural abundance 13C. Studies involving less soluble compounds, higher molecular weight materials or relatively rapid reactions may often be carried out using 13C enrichment. Because NMR spectroscopy is non-destructive, it has proven to be extremely useful in the study of natural product biosynthetic pathways. Another area where important applications are being made is in the study of enzymatic and non-enzymatic reaction mechanisms. The characteristics of the 18O isotope shift in 13C NMR spectroscopy are reviewed. Several examples from the work of other groups in the area of natural product biosynthesis are briefly mentioned. This is followed by a number of illustrative applications in the area of bioorganic and enzymatic reaction mechanism that have been examined in our laboratory. The enzymatic examples include acid phosphatases, epoxide hydratase, acetylcholinesterase and asparaginase. 20 refs.; 1 figure

  13. UV-laser-based microscopic dissection of tree rings - a novel sampling tool for δ(13) C and δ(18) O studies.

    Schollaen, Karina; Heinrich, Ingo; Helle, Gerhard

    2014-02-01

    UV-laser-based microscopic systems were utilized to dissect and sample organic tissue for stable isotope measurements from thin wood cross-sections. We tested UV-laser-based microscopic tissue dissection in practice for high-resolution isotopic analyses (δ(13) C/δ(18) O) on thin cross-sections from different tree species. The method allows serial isolation of tissue of any shape and from millimetre down to micrometre scales. On-screen pre-defined areas of interest were automatically dissected and collected for mass spectrometric analysis. Three examples of high-resolution isotopic analyses revealed that: in comparison to δ(13) C of xylem cells, woody ray parenchyma of deciduous trees have the same year-to-year variability, but reveal offsets that are opposite in sign depending on whether wholewood or cellulose is considered; high-resolution tree-ring δ(18) O profiles of Indonesian teak reflect monsoonal rainfall patterns and are sensitive to rainfall extremes caused by ENSO; and seasonal moisture signals in intra-tree-ring δ(18) O of white pine are weighted by nonlinear intra-annual growth dynamics. The applications demonstrate that the use of UV-laser-based microscopic dissection allows for sampling plant tissue at ultrahigh resolution and unprecedented precision. This new technique facilitates sampling for stable isotope analysis of anatomical plant traits like combined tree eco-physiological, wood anatomical and dendroclimatological studies. PMID:24219751

  14. Atomic transport mechanisms in thin oxide films grown on zirconium by thermal oxidation, as-derived from 18O-tracer experiments

    Two-stage oxidation experiments using 16O and 18O isotopes were performed to reveal the governing atomic transport mechanism(s) in thin (thickness ¯0) single-crystalline surfaces were prepared under ultra-high vacuum conditions by a cyclic treatment of alternating ion-sputtering and in vacuo annealing steps. Next, the bare Zr surfaces were oxidized at 450 K and at pO2 = 1 × 10−4 Pa, first in 16O2(g) and subsequently in 18O2(g). The 18O-tracer depth distributions in the oxide films were recorded by time-of-flight secondary ion mass spectrometry. It was concluded that the early stage of the oxidation process is governed by oxygen transport to the metal/oxide interface through the lattice and along the grain boundaries of the nanosized oxide grains whereas, on continuing oxidation, only oxygen lattice transport controls the oxidation process. An oxide-film growth mechanism is proposed.

  15. Direct evidence for the origin of low-18O silicic magmas: quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

    Bacon, C.R.; Adami, L.H.; Lanphere, M.A.

    1989-01-01

    Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower ??18O values (-3.4 to +4.9???) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0???). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T ??? 900??C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ??? 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have ??18O values ??? 0.5??? or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18O depletion in large, shallow silicic magma bodies. ?? 1989.

  16. Direct evidence for the origin of low-18O silicic magmas: Quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

    Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower δ18O values (-3.4 to +4.9per mille) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0per mille). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T≥900deg C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ≅ 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have δ18O values ≅ 0.5per mille or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18O depletion in large, shallow silicic magma bodies. (orig.)

  17. Estimated values of the environmental tritium concentration and the altitude isotope effects of δD and δ18O in Hokkaido

    Tritium (3H) concentration and stable isotopic ratios δD and δ18O are important environmental tracer data. In Hokkaido, however, hydrological studies using these data were difficult due to a lack of environmental tritium and the altitude isotope effect values. In this study, 3H concentrations of Hokkaido wine were measured to estimate the past rain 3H concentrations. In addition, environmental δD and δ18O samples taken on Mt. Daisetsuzan, the highest peak in Hokkaido, and in the Tokachi Plain were measured. The results obtained are as follows: Estimated concentrations of 3H in Hokkaido were higher than those in Tokyo and Tsukuba, and were consistent with geographical 3H levels in rain around Hokkaido. Some model calculations suggested that the 3H concentrations in the 1950's and 1960's were at least 30% higher than those in Tokyo. The altitude isotope effects obtained were -1.75±0.30 per mille/100 m and -0.24±0.01 per mille/100 m for δD and δ18O, respectively. These values are almost the same as, or slightly lower than those in the Chubu and Tohoku districts. Using these data, the approximate age of groundwater and the altitude of original precipitation could be estimated. (author)

  18. Simultaneous 13C/12C and (18)O/(16)O isotope ratio measurements on CO2 based on off-axis integrated cavity output spectroscopy.

    Jost, Hans-Jürg; Castrillo, Antonio; Wilson, H William

    2006-03-01

    A prototype off-axis integrated cavity output spectrometer (OA-ICOS) utilizing two identical cavities together with a near-infrared (1.63 microm) external cavity tunable diode laser is described. The two-cavity design-one for a reference gas and one for a sample gas-takes advantage of classical double-beam infrared spectrometer characteristics in reducing uncertainties due to laser scan or power instabilities and major temperature variations by a factor of three or better compared with a single-cavity scheme. This is the first OA-ICOS instrument designed to determine 13C/12C and (18)O/(16)O ratios from CO2 rotation/vibration fine structure in three different combination bands. Preliminary results indicate that at 0.8 Hz a precision of 3.3 and 2.8 per thousand is obtained for delta13C and delta(18)O, respectively, over a period of 10 h and a pure CO2 gas sample at 26 hPa. By averaging 100 spectra over a subset of the data, we achieved a precision of 1.6 and 0.8 \\permil\\ for delta13C and delta(18)O, respectively. PMID:16500753

  19. Abrupt climate change of East Asian Monsoon at 130 kaBP inferred from a high resolution stalagmite δ18O record

    JIANG Xiuyang; WANG Yongjin; KONG Xinggong; WU Jiangying; SHAO Xiaohua; XIA Zhifeng; CHENG Hai

    2005-01-01

    230Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize the East Asian Monsoon precipitation from 133 to127 ka. The decadal-scale high-resolution δ18O record reveals a detailed transitional process from the Penultimate Glaciation to the Last Interglaciation. As established with 230Th dates, the age of the Termination II is determined to be 129.5±1.0 kaBP, which supports the Northern Hemisphere insolation as the triggers for the ice-age cycles. In our δ18O record, the glacial/ interglacial fluctuation reaches about 4‰, almost the same level as in other Asian Monsoon cave stalagmite δ18O records. The transition of the glacial/interglacial period in our record can be recognized as four stepwise stages, among which, a rapid rise of monsoon precipitation follows the stage of "Termination II pause". The rapid rise is synchronous with the abrupt change of global methane concentration, which reflects that an increase in both Asian Monsoon precipitation and tropical wetland plays an important role in the global climate changes.

  20. Low 18O terranes tracking mesozoic climates in the South Pacific : a 25-year search in the BRF-5 Laboratory, Southern Section

    Substantially negative delta 18O values of altered rocks are an unfailing guide to 18O-depleted meteoric water of low mean annual temperature, and therefore of cold climates at times of hydrothermal alteration. However, because water-rock interaction is often incomplete even where it has occurred, the lack of depleted values is poor evidence for lack of cold climate. A now established average surface rock composition of -6.6 per thousand delta 18O, with a lower limit of -16 per thousand, for an igneous and metamorphic terrane of some 6,000 km/sup 2/ in West Antarctic indicates Cretaceous meteoric water of less, or much less, than -20 per thousand. This new anomaly and similar anomalies in New Zealand date from before rifting along the Antarctic-Pacific Rise and are tracking terranes originating from the Mesozoic South polar archipelago. In this area subaerial, or subglacial, hydrothermal isotope exchange has been particularly effective, and/or meteoric waters were isotopically unusually depleted. The discovery, mapping and dating of further isotopically depleted zones in the geological record will improve constraints for Paleozoic and Mesozoic greenhouse climates. A brief account is given of practical and conceptual highlights in the running of the oxygen extraction line originally brought to New Zealand by Professor Bob Clayton. (author)

  1. Ice Core Depth-Age Relation for Vostok delta-D and Dome Fuji delta-18O Records Based on the Devils Hole Paleotemperature Chronology

    Landwehr, Jurate Maciunas

    2002-01-01

    This report presents the data for the Vostok - Devils Hole chronology, termed V-DH chronology, for the Antarctic Vostok ice core record. This depth - age relation is based on a join between the Vostok deuterium profile (D) and the stable oxygen isotope ratio (18O) record of paleotemperature from a calcitic core at Devils Hole, Nevada, using the algorithm developed by Landwehr and Winograd (2001). Both the control points defining the V-DH chronology and the numeric values for the chronology are given. In addition, a plausible chronology for a deformed bottom portion of the Vostok core developed with this algorithm is presented. Landwehr and Winograd (2001) demonstrated the broader utility of their algorithm by applying it to another appropriate Antarctic paleotemperature record, the Antarctic Dome Fuji ice core 18O record. Control points for this chronology are also presented in this report but deemed preliminary because, to date, investigators have published only the visual trace and not the numeric values for the Dome Fuji 18O record. The total uncertainty that can be associated with the assigned ages is also given.

  2. The use of 18O-exchange and base-catalyzed N-dealkylation with liquid chromatography/tandem mass spectrometry to identify carbinolamide metabolites.

    Bessire, Andrew J; Vaz, Alfin D N; Walker, Gregory S; Wang, Wei Wei; Sharma, Raman

    2010-07-30

    Oxidation of N-alkyl-substituted amides is a common transformation observed in metabolism studies of drugs and other chemicals. Metabolism at the alpha carbon atom can produce stable carbinolamide compounds, which may be abundant enough to require complete confidence in structural assignments. In a drug discovery setting, rapid structural elucidation of test compounds is critical to inform the compound selection process. Traditional approaches to the analysis of carbinolamides have relied upon the time-consuming synthesis of authentic standards or purification of large enough quantities for characterization by nuclear magnetic resonance (NMR). We describe a simple technique used in conjunction with liquid chromatography/tandem mass spectrometry (LC/MS/MS) which demonstrates the chemical identity of a carbinolamide by its distinctive ability to reversibly exchange [(18)O]water through an imine intermediate. A key advantage of the technique is that the chromatographic retention times of metabolites are preserved, allowing direct comparisons of mass chromatograms from non-treated and [(18)O]water-treated samples. Metabolites susceptible to the treatment are clearly indicated by the addition of 2 mass units to their original mass. An additional test which can be used in conjunction with (18)O-exchange is base-catalyzed N-dealkylation of N-(alpha-hydroxy)alkyl compounds. The use of the technique is described for carbinolamide metabolites of dirlotapide, loperamide, and a proprietary compound. PMID:20552706

  3. Characterization of the water chemistry, sediment (13)C and (18)O compositions of Kolleru Lake-a Ramsar wetland in Andhra Pradesh, India.

    Das Sharma, Subrata; Sujatha, D

    2016-07-01

    The chemistry of surface water sampled at different locations of the Kolleru Lake in Andhra Pradesh (India) show heterogeneous variability. The concentrations of dissolved sodium and chloride ions, total dissolved solids (TDS) together with high conductivity documented in water samples are indicative of mixing of saline seawater. This interpretation is further corroborated by enriched δ(18)O compositions of the carbonate fraction of the surface sediments collected at the same locations (as that of water) of the lake, and fairly good positive correlations of δ(18)O -Na(+) and δ(18)O-TDS. The saline water intrusion into the lake appears to be resulted due to its near stagnant to dry condition with reduced inflow and outflow. Such dry condition facilitated seawater intrusion into the lake due to several reasons: (i) proximity of lake to the sea (~35 km), (ii) overexploitation of fresh groundwater for agriculture as well as livestock farming, and (iii) incursion of tidal seawater (high sea waves) through Upputeru River, which is directly linked to the sea. We also document highly heterogeneous distribution of certain potentially toxic metal ions like chromium, copper, manganese, and zinc in the lake waters. Indiscriminate disposal of domestic and industrial effluents around the lake appears to be responsible for the presence of potentially toxic heavy metals. Based on these results, we finally suggest some measures for environmental rehabilitation of the lake and its surroundings. PMID:27312252

  4. Large-Scale Multiplexed Quantitative Discovery Proteomics Enabled by the Use of an 18O-Labeled “Universal” Reference Sample

    Qian, Wei-Jun; Liu, Tao; Petyuk, Vladislav A.; Gritsenko, Marina A.; Petritis, Brianne O.; Polpitiya, Ashoka D.; Kaushal, Amit; Xiao, Wenzhong; Finnerty, Celeste C.; Jeschke, Marc G.; Jaitly, Navdeep; Monroe, Matthew E.; Moore, Ronald J.; Moldawer, Lyle L.; Davis, Ronald W.; Tompkins, Ronald G.; Herndon, David N.; Camp, David G.; Smith, Richard D.

    2009-01-01

    The quantitative comparison of protein abundances across a large number of biological or patient samples represents an important proteomics challenge that needs to be addressed for proteomics discovery applications. Herein, we describe a strategy that incorporates a stable isotope 18O-labeled ″universal″ reference sample as a comprehensive set of internal standards for analyzing large sample sets quantitatively. As a pooled sample, the 18O-labeled ″universal″ reference sample is spiked into each individually processed unlabeled biological sample and the peptide/protein abundances are quantified based on 16O/18O isotopic peptide pair abundance ratios that compare each unlabeled sample to the identical reference sample. This approach also allows for the direct application of label-free quantitation across the sample set simultaneously along with the labeling-approach (i.e., dual-quantitation) since each biological sample is unlabeled except for the labeled reference sample that is used as internal standards. The effectiveness of this approach for large-scale quantitative proteomics is demonstrated by its application to a set of 18 plasma samples from severe burn patients. When immunoaffinity depletion and cysteinyl-peptide enrichment-based fractionation with high resolution LC-MS measurements were combined, a total of 312 plasma proteins were confidently identified and quantified with a minimum of two unique peptides per protein. The isotope labeling data was directly compared with the label-free 16O-MS intensity data extracted from the same data sets. The results showed that the 18O reference-based labeling approach had significantly better quantitative precision compared to the label-free approach. The relative abundance differences determined by the two approaches also displayed strong correlation, illustrating the complementary nature of the two quantitative methods. The simplicity of including the 18O-reference for accurate quantitation makes this

  5. Toward the Inference of Deglacial Ocean Dynamics from the Spatial Pattern of LGM-to-Modern d13C and d18O Change

    Gebbie, G.; Peterson, C. D.; Lisiecki, L. E.; Spero, H. J.

    2014-12-01

    Estimates of the whole-ocean d13C change between the Last Glacial Maximum (LGM) and the modern-day are converging to values of about 0.4 per mil, and are of great use in partitioning land versus ocean contributions to the deglacial carbon cycle. To determine which specific oceanic processes are at play, however, knowledge of the spatial pattern of LGM-to-modern d13C and d18O change is critical. Spatial maps have mostly focused on Atlantic d13C, with less progress for d18O and the Pacific and Indian sectors, due to the concentration of sediment-core observations in the Atlantic and the difficulty in making meaningful maps from sparse data. Here, we demonstrate that a state estimation (or data assimilation) method based on recently compiled data and a simple kinematic ocean model simultaneously produces reasonable results for: 1) global maps of d13C and d18O, 2) uncertainty in the estimated properties, and 3) oceanic water-mass geometry. The observations include benthic d13C and d18O data from 493 marine sediment cores that were collected from the scientific literature and NOAA, PANGEA, and Delphi databases. The kinematic model permits each data point to have influence both up- and downstream along a water-mass pathway, typically allowing a larger geographical range than a statistical interpolation method. No assumption regarding the state of the circulation is necessary, and the modern-day circulation need not be assumed to be representative of the LGM. With this method, meridional (or other) sections can be compared between ocean basins. Furthermore, the internally-consistent d18O and d13C maps are used to determine the LGM-to-modern spatial changes that are robust given the uncertainty and sparsity of data. Rather than simply focus on property maps, we suggest that the link between observations and circulation changes (as reflected by the paths that water travels), points the way toward dynamical processes that must be explained. A particular application of our

  6. Isotopic variations ({delta}{sup 13} C and {delta}{sup 18} O) in Siderastrea stellata (Cnidaria-Anthozoa), Itamaraca island, State of Pernambuco, Northeastern Brazil

    Ferreira, Valderez P.; Sial, Alcides N. [Pernambuco Univ., Recife, PE (Brazil). Dept. de Geologia. Lab. de Isotopos Estaveis; Mayeal, Elga M.; Exner, Marco Antonio [Pernambuco Univ., Recife, PE (Brazil). Dept. de Zoologia. Lab. de Macro e Megabentos

    1998-12-01

    Isotopic determinations for O and C were performed in coral skeletons collected in beach rocks from two localities (Orange and Catuama), Itamaraca Island, north littoral of the State of pernambuco, northeastern Brazil. Large variations of {delta}{sup 18} O and {delta}{sup 13} C in corals from both localities are found, the largest ones being observed at the Orange locality {delta}{sup 13} C in this locality varies from -0.8 to +1.8% PDB and {delta}{sup 1.8} O from -5.3 to -1.8% PDB, while at the Catuama locality, they vary from -1.8 to 0.1% PDB and -3.8 to -2.7% PDB, respectively. Large variations in {delta}{sup 18} O (up to 2.5%) coupled with weakly defined positive correlation between {delta}{sup 18} O and {delta}{sup 13} C, can be attributed to temperature variations as consequence of climatic perturbations. Temperature estimates, calculated from {delta}{sup 18} O values, assuming isotopic equilibrium with seawater, yield values between 24.9 deg C and 43.1 deg C at Orange, and from 28.4 deg C to 35 deg C at Catuama, all of them (expect one growth band from one sample) are high enough for the full development of the coral colony. Temperature average is 31.4 deg C at Orange, which is a little bit higher than that at Catuama, but both of them indicate thermal stress conditions. In all analyzed specimens, expect for one, at Orange, T increases was accompanied by decreasing in the organic activity, as suggested by corresponding negative {delta}{sup 13} C anomaly. Therefore, the observed bleaching is possibly related to thermal stress and the high T may be related to the El Nino-Southern Oscillation (ENSO) warning event. On the other hand, anthropogenic action at Orange, local of intense tourism throughout the year, coupled with high rate of sedimentation in the region, may contribute to the observed coral bleaching. (author)

  7. Reconstructing lake evaporation history and the isotopic composition of precipitation by a coupled δ18O-δ2H biomarker approach

    Hepp, Johannes; Tuthorn, Mario; Zech, Roland; Mügler, Ines; Schlütz, Frank; Zech, Wolfgang; Zech, Michael

    2015-10-01

    Over the past decades, δ18O and δ2H analyses of lacustrine sediments became an invaluable tool in paleohydrology and paleolimnology for reconstructing the isotopic composition of past lake water and precipitation. However, based on δ18O or δ2H records alone, it can be challenging to distinguish between changes of the precipitation signal and changes caused by evaporation. Here we propose a coupled δ18O-δ2H biomarker approach that provides the possibility to disentangle between these two factors. The isotopic composition of long chain n-alkanes (n-C25, n-C27, n-C29, n-C31) were analyzed in order to establish a 16 ka Late Glacial and Holocene δ2H record for the sediment archive of Lake Panch Pokhari in High Himalaya, Nepal. The δ2Hn-alkane record generally corroborates a previously established δ18Osugar record reporting on high values characterizing the deglaciation and the Older and the Younger Dryas, and low values characterizing the Bølling and the Allerød periods. Since the investigated n-alkane and sugar biomarkers are considered to be primarily of aquatic origin, they were used to reconstruct the isotopic composition of lake water. The reconstructed deuterium excess of lake water ranges from +57‰ to -85‰ and is shown to serve as proxy for the evaporation history of Lake Panch Pokhari. Lake desiccation during the deglaciation, the Older Dryas and the Younger Dryas is affirmed by a multi-proxy approach using the Hydrogen Index (HI) and the carbon to nitrogen ratio (C/N) as additional proxies for lake sediment organic matter mineralization. Furthermore, the coupled δ18O and δ2H approach allows disentangling the lake water isotopic enrichment from variations of the isotopic composition of precipitation. The reconstructed 16 ka δ18Oprecipitation record of Lake Panch Pokhari is well in agreement with the δ18O records of Chinese speleothems and presumably reflects the Indian Summer Monsoon variability.

  8. Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy II: Insight from a climate transect study

    Tuthorn, Mario; Zech, Michael; Ruppenthal, Marc; Oelmann, Yvonne; Kahmen, Ansgar; Valle, Héctor Francisco del; Wilcke, Wolfgang; Glaser, Bruno

    2014-02-01

    The oxygen isotopic composition of precipitation (δ18Oprec) is well known to be a valuable (paleo-)climate proxy. Paleosols and sediments and hemicelluloses therein have the potential to serve as archives recording the isotopic composition of paleoprecipitation. In a companion paper (Zech et al., 2014) we investigated δ18Ohemicellulose values of plants grown under different climatic conditions in a climate chamber experiment. Here we present results of compound-specific δ18O analyses of arabinose, fucose and xylose extracted from modern topsoils (n = 56) along a large humid-arid climate transect in Argentina in order to answer the question whether hemicellulose biomarkers in soils reflect δ18Oprec. The results from the field replications indicate that the homogeneity of topsoils with regard to δ18Ohemicellulose is very high for most of the 20 sampling sites. Standard deviations for the field replications are 1.5‰, 2.2‰ and 1.7‰, for arabinose, fucose and xylose, respectively. Furthermore, all three hemicellulose biomarkers reveal systematic and similar trends along the climate gradient. However, the δ18Ohemicellulose values (mean of the three sugars) do not correlate positively with δ18Oprec (r = -0.54, p fucose and xylose do not simply reflect δ18Oprec but rather δ18Oleaf water. The correlation between measured δ18Ohemicellulose and modeled δ18Oleaf water is highly significant (r = 0.81, p < 0.001, n = 20). This finding can be attributed to the evaporative 18O enrichment of leaf water during transpiration. Model sensitivity tests using a Péclet-modified Craig-Gordon (PMCG) model corroborate that relative air humidity is a very rigorous climate parameter influencing δ18Oleaf water, whereas temperature is of minor importance. While oxygen exchange and degradation effects on δ18O values of hemicelluloses sugar biomarkers seem to be negligible (Zech et al., 2012), further effects that need to be considered when interpreting δ18Ohemicellulose

  9. Using stable isotope analyzes (δ18O) and geochemistry monitoring of mountain springs (Friuli Venezia Giulia, Northern Italy)

    Full text: Optimum protection and management of water resources is a priority objective in industrialized northern Italy. Reconciling environmental protection with human needs requires an accurate and up-to-date assessment of the available resources. In this light, the ARPA FVG (Regional Environmental Protection Unit) and the GGACI of the University of Trieste have created a monitoring network for thirteen mountains springs that have been recognized as general indications of the water sources for the region. These water springs are located at altitudes that range from 35 m a.s.l. to 885 m a.s.l and have mean discharges varying from l/s to m3/s. These springs are fairly variable for local importance, water discharges and geological nature but has been chosen as indicative of all the springs of the region. From September 2004 samples have been collected on a monthly basis both from the water springs and from local precipitations in order to get the isotopic and physical and chemical water signatures. In addition, a geological survey of the thirteen areas, has been done to delineate the hydro-structural influences on spring locations. Isotopical analyzes (δ18O) have been measured by mass spectrometric techniques at the University of Trieste and the conventional values ((δ) are reported as per mil deviations from the V-SMOW standard. Chemical analyzes were done by atomic absorption spectrophotometry and HCL titration for carbonate. The physical and chemical parameters recorded are water temperature, EC, pH, TH, anion (HCO3, NO3, Cl, SO4, F, SiO3) and cation (K, Na, Mg, Ca, NH4) concentrations as well as Si contents. Chemical interpretations have been elaborate using the Aquachem software, while for spatial data ArcGis has been used. The isotopical data has delineate the springs that have fast water circulations or superficial and that therefore are more vulnerable to pollution and has given the altitudes of the recharging areas. The chemical analyzes have detected

  10. Speleothem calcite farmed in situ: Modern calibration of δ 18O and δ 13C paleoclimate proxies in a continuously-monitored natural cave system

    Tremaine, Darrel M.; Froelich, Philip N.; Wang, Yang

    2011-09-01

    Understanding the relationships between speleothem stable isotopes (δ 13C δ 18O) and in situ cave forcing mechanisms is important to interpreting ancient stalagmite paleoclimate records. Cave studies have demonstrated that the δ 18O of inorganically precipitated (low temperature) speleothem calcite is systematically heavier than the δ 18O of laboratory-grown calcite for a given temperature. To understand this apparent offset, rainwater, cave drip water, groundwater, and modern naturally precipitated calcite (farmed in situ) were grown at multiple locations inside Hollow Ridge Cave in Marianna, Florida. High resolution micrometeorological, air chemistry time series and ventilation regimes were also monitored continuously at two locations inside the cave, supplemented with periodic bi-monthly air gas grab sample transects throughout the cave. Cave air chemistry and isotope monitoring reveal density-driven airflow pathways through Hollow Ridge Cave at velocities of up to 1.2 m s -1 in winter and 0.4 m s -1 in summer. Hollow Ridge Cave displays a strong ventilation gradient in the front of the cave near the entrances, resulting in cave air that is a mixture of soil gas and atmospheric CO 2. A clear relationship is found between calcite δ 13C and cave air ventilation rates estimated by proxies pCO 2 and 222Rn. Calcite δ 13C decreased linearly with distance from the front entrance to the interior of the cave during all seasons, with a maximum entrance-to-interior gradient of Δδ 13C CaCO3 = -7‰. A whole-cave "Hendy test" at multiple contemporaneous farming sites reveals that ventilation induces a +1.9 ± 0.96‰ δ 13C offset between calcite precipitated in a ventilation flow path and calcite precipitated on the edge or out of flow paths. This interpretation of the "Hendy test" has implications for interpreting δ 13C records in ancient speleothems. Calcite δ 13C CaCO3 may be a proxy not only for atmospheric CO 2 or overlying vegetation shifts but also for

  11. The δ15N and δ18O values of N2O produced during the co-oxidation of ammonia by methanotrophic bacteria

    Mandernack, Kevin W.; Mills, Christopher T.; Johnson, Craig A.; Rahn, Thomas; Kinney, Chad

    2009-01-01

    In order to determine if the δ15N and δ18O values of N2O produced during co-oxidation of NH4+ by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N2O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH4Cl as an oxidation substrate. The N2O produced during NH4+ oxidation by methanotrophic bacteria showed nitrogen isotope fractionation between NH4+ and N2O (εN2O–NH4+) of − 48 and − 55‰ for Methylomonas methanica and Methylosinus trichosporium, OB3b respectively. These large fractionations are similar to those previously measured for autotrophic nitrifying bacteria and consistent with N2O formation by multiple rate limiting steps that include NH4+oxidation by the methane monooxygenase enzyme and reduction of NO2− to N2O. Consequently, N2O formed by NH4+ oxidation via methanotrophic or autotrophic nitrifying bacteria might generally be characterized by lower δ15NN2O values than that formed by denitrificaiton, although this also depends on the variability of δ15N of available nitrogen sources (e.g., NH4+, NO3−, NO2−). Additional incubations with M. trichosporium OB3b at high and low CH4 conditions in waters of different δ18O values revealed that 19–27% of the oxygen in N2O was derived from O2 with the remainder from water. The biochemical mechanisms that could explain this amount of O2 incorporation are discussed. The δ18O of N2O formed under high CH4 conditions was ~ + 15‰ more positive than that formed under lower CH4 conditions. This enrichment resulted in part from the incorporation of O2 into N2O that was enriched in 18O due to an isotope fractionation effect of − 16.1 ± 2.0‰ and − 17.5 ± 5.4‰ associated with O2 consumption during the high and low methane concentration incubations, respectively. Therefore, N2O formed by NH4+

  12. Constraining the origin of the Messinian gypsum deposits using coupled measurement of δ^{18}O$/δD in gypsum hydration water and salinity of fluid inclusions

    Evans, Nicholas P.; Gázquez, Fernando; McKenzie, Judith A.; Chapman, Hazel J.; Hodell, David A.

    2016-04-01

    We used oxygen and hydrogen isotopes of gypsum hydration water (GHW) coupled with salinity deduced from ice melting temperatures of primary fluid inclusions in the same samples (in tandem with 87Sr/86Sr, δ34S and other isotopic measurements) to determine the composition of the mother fluids that formed the gypsum deposits of the Messinian Salinity Crisis from shallow and intermediate-depth basins. Using this method, we constrain the origin of the Messinian Primary Lower Gypsum (PLG) of the Sorbas basin (Betic foreland) and both the Upper Gypsum (UG) and the Lower Gypsum of the Sicilian basin. We then compare these results to measurements made on UG recovered from the deep Ionian and Balearic basins drilled during DSDP Leg 42A. The evolution of GHW δ18O/δD vs. salinity is controlled by mixing processes between fresh and seawater, coupled with the degree of evaporation. Evaporation and subsequent precipitation of gypsum from fluids dominated by freshwater will result in a depressed 87Sr/86Sr values and different trajectory in δ18O/δD vs. salinity space compared to fluids dominated by seawater. The slopes of these regression equations help to define the end-members from which the fluid originated. For example, salinity estimates from PLG cycle 6 in the Sorbas basin range from 18 to 51ppt, and after correction for fractionation factors, estimated δ18O and δD values of the mother water are low (-2.6 salinity) are within error of the average isotope composition of the modern precipitation and groundwater in this region of SE Spain. This indicates there was a significant contribution of meteoric water during gypsum deposition, while 87Sr/86Sr (0.708942 salinities of fluid inclusions are higher averaging ˜100ppt. In contrast to cycle 6, the intercepts of the regression equations of cycle 2 display more positive δ18O/δD values. While the estimated range in δ18O and δD of the mother water and salinities fall below those expected from the evaporation of seawater

  13. Using stable isotope analyzes (δ18O) to characterize the regional hydrology of the Friuli Venezia Giulia plain, north-east Italy

    Full text: The Friuli Venezia Giulia plain, located in the northeastern sector of Italy, support most of the agricultural and industrial activities of the region. From a geomorphological and hydrogeological prospective this plain is subdivided in two provinces which are separated by a resurgence line. The Upper Friuli Plain is mostly composed of calcareous and dolomitic gravels and host a well developed phreatic aquifer. The Lower Friuli Plain is characterized by multi-layered artesian aquifers that are composed of gravels and sand interbedded by clay and silty layers that become thicker in a southwards direction. The constant increase of water demand, has led the local authorities (ARPA FVG, Regional Environmental Protection Unit) to begun an evaluation at large scale of the hydrological fluxes and used of this plain creating a collaborative project with the GGACI group (Water and Geomorphologic Research Unit) of the University of Trieste. This project focuses on the water chemistry and on stable isotope investigations (δ18O) from precipitation samples and groundwaters from the major aquifer types in the region. Chemical analyzes were done by ARPA FVG, whilst the stable isotopic composition of water samples has been measured by mass spectrometric techniques at the University of Trieste. The oxygen isotope composition (δ18O) was measured by means of water-CO2 equilibration technique at 25oC. The conventional δ-notation is used and the values are reported as per mil deviations from the V-SMOW standard. Thirteen pluviometers have been positioned in different areas of the region from September 2004 in order to characterize the oxygen stable signature of precipitations. Weighted mean δ18O values of precipitation range from -7.7 %o to -10.5 %o (with a mean value of -9.1 %o) in the mountain areas and from -6.7 %o to -7.6 %o in the plain (with a mean value of -7.1%o). The calculated vertical isotope gradient is 0.29 %o in accord to the ones measured in other Italian

  14. Effects of land use on the distribution of stable isotopes of water (18O/2H) in a deep unconfined aquifer and its role for recharge estimates.

    Müller, Sascha; Jessen, Søren; Engesgaard, Peter; Jari Leskelä, Jari

    2014-05-01

    Soil evaporation, transpiration and interception varies with land use, such as forest, heath and agriculture, encountered within a catchment. Therefore land use variations may give rise to different isotopic compositions of water recharging an aquifer. We investigated the distribution of stable isotopes of water in an unconfined aquifer at Rabis Creek, Denmark, consisting of up to ~100 m glacio-fluvial sand overlying a clay aquitard. The aquifer has an unsaturated zone of 15 m, assumed to effectively dampen out any seasonal variation in the isotopic composition of recharging water once it arrives to the groundwater table. In addition, the aquifer is situated under different land uses; arable land, forest and heath, and does not receive infiltrating water from surface water bodies. Water samples, analyzed for stable isotopes of water and major ion concentrations, were obtained from eight multi-level wells, sampling up to 21 m below the water table along a 3 km long transect parallel to the general groundwater flow direction. Groundwater derived from recharge in arable areas could be easily traced by its elevated NO3 concentrations (typically 30 to 80 mg/L), whereas NO3 was almost absent in groundwater derived from forest and heath areas. NO3 enriched water formed plumes extending with the flow direction into the deeper parts of the aquifer covered by forest and heath. The δ18O values in the aquifer varied up to 1‰ between 7.5‰ and 8.5‰. Highest depletion values occurred in the proximity of the NO3 plumes. This indicates a certain signal in the δ18O originating from agricultural sites. Furthermore, within the first meters a steady depletion downwards was observed where at a certain depth a jump in depletion occurred. This δ18O distribution suggests a zone dominated by vertical flows influenced by diffuse mixing with horizontal flowing groundwater in the upper part of the aquifer and beneath a zone of dominating horizontal flows with stronger mixing. The 18O

  15. Climatic fluctuations and seasonality during the Late Jurassic (Oxfordian-Early Kimmeridgian) inferred from δ18O of Paris Basin oyster shells

    Brigaud, Benjamin; Pucéat, Emmanuelle; Pellenard, Pierre; Vincent, Benoît; Joachimski, Michael M.

    2008-08-01

    Oxygen isotope data from biostratigraphically well-dated oyster shells from the Late Jurassic of the eastern Paris Basin are used to reconstruct the thermal evolution of western Tethyan surface waters during the Early Oxfordian-Early Kimmeridgian interval. Seventy eight oyster shells were carefully screened for potential diagenetic alteration using cathodoluminescence microscopy. Isotope analyses were performed on non-luminescent parts of shells (n = 264). Intra-shell δ18O variability was estimated by microsampling along a transect perpendicular to the growth lines of the largest oyster shell. The sinusoidal distribution of the δ18O values along this transect and the dependence of the amplitude of variations with bathymetry suggest that intra-shell variability reflects seasonal variations of temperature and/or salinity. Average amplitudes of about 5 °C in shallow water environments and of about 2-3 °C in deeper offshore environments are calculated. These amplitudes reflect minimum seasonal temperature variation. Our new data allow to constrain existing paleotemperature trends established from fish tooth and belemnite δ18O data and are in better agreement with paleontological data. More specifically, a warming trend of about 3 °C is reconstructed for oceanic surface waters during the Early to Middle Oxfordian transition, with maximum temperatures reaching 24 °C in the transversarium Zone (late Middle Oxfordian). From the transversarium Zone to the bimmamatum Zone, a cooling of about 7 °C is indicated, whereas from the bimmamatum Zone, temperatures increased again by about 7 °C to reach 24 °C in average during the cymodoce Zone (Early Kimmeridgian).

  16. Results of long term investigations on 18O in the unsaturated zone in comparison to the results of tracing experiments and numerical modeling

    An observation station of infiltration water is in operation at Wagna in the porous groundwater field of Leibnitz in Southern Styria (Austria) since 1991. Numerous parameters are being measured continuously in the unsaturated zone in different depths under two fields of different agricultural cultivation, the infiltration water being sampled under disturbed and undisturbed conditions. Tracer investigations has been done in 1993, 1997 and 2001 using bromide and 2H to detect the residence time of infiltration water from the surface to the groundwater table (mean average: 4.5 m below surface) and to evaluate transport parameters for the different compartments of soil and unsaturated gravel and sand as a basis for the calibration of numerical solute transport models. From 1991 to 2000 the content of 18O has been detected in precipitation water and in seepage water in different depths of the unsaturated zone as well as in the groundwater itself. The time series of the concentration of 18O in precipitation (mean weighted monthly values from sampling site Graz-Universitaet) and in the soil water at the research station of Wagna 0.4 m below surface is shown. As an example it is visible that the amplitude of 18O in soil water is lower than in precipitation water and that the curve is shifted of about +4 months at the time scale. Due to the intensive investigations on tracing experiments and on numerical modeling at the test field Wagna it will be possible to discuss isotope data evaluation methods used in the unsaturated zone in comparison to the results of tracing experiments and modeling results. On the other hand the long term observation at different depths will give the possibility for better calibration of the numerical transport models on the behaviour of nitrogen from agriculture

  17. Study of Leachate Contamination in Bantar Gebang Landfill to Its Shallow Groundwater using Natural Isotope Tracers of 18O, 2H and 3H

    E.R. Pujiindiyati

    2015-04-01

    Full Text Available Leaching from Bantar Gebang landfill, Jakarta’s main municipal landfill, especially from its two waste water treatment plants (plant A in zone-3 and plant B in Sumur Batu to underlying aquifer has been studied using isotope techniques. The study was based on the abundances of the heavier isotopes in water molocules namely 18O, 2H (deuterium and 3H (tritium. Because both water in the waste-water treatment plants and groundwater have undergone different independent physical processes, it was assumed that each water source has its own typical finger-print in term of the abundances of 18O, 2H (deuterium and 3H (tritium. Leachate from the two waste water treatment plants have higher 2H, 3H activities, and physical parameters (EC, TDS, and pH values than those of groundwater samples. Because of the age and size of the two waste water treatment plants are significantly different, it was also observed that the isotope contents of plant B, younger age and smaller size, was relatively lower in 2H values and 3H activities compared to those of plant A. These phenomena have been used to identify the leaching from waste-water treatment plants of Bantar Gebang landfill to the underlying aquifer. During the dry season, it was observed that 2H values in leachate were generally higher than those in rainy season. This result might be due to the extensive methane production in the treatment plants. Conversely, 18O-shifting in leachate from local meteoric line indicated that the leachate had experienced evaporation. Buried luminescent paints in the landfill were most likely the source of high tritium activity in leachate. Based on the samples collected from the study area (mostly from dug or bore wells, it was found that the underlying aquifer especially shallow groundwater has been contaminated up to as high as 33% with leachate

  18. Study of leachate contamination in Bantar Gebang landfill to its shallow groundwater using natural isotope tracers of 18O, 2H and 3H

    Leaching from Bantar Gebang landfill, Jakarta’s main municipal landfill, especially from its two waste water treatment plants (plant A in zone-3 and plant B in Sumur Batu) to underlying aquifer has been studied using isotope techniques. The study was based on the abundances of the heavier isotopes in water molecules namely 18O, 2H (deuterium) and 3H (tritium). Because both water in the waste-water treatment plants and groundwater have undergone different independent physical processes, it was assumed that each water source has its own typical finger-print in term of the abundances of 18O, 2H (deuterium) and 3H (tritium). Leachate from the two waste water treatment plants have higher 2H, 3H activities, and physical parameters (EC, TDS, and pH) values than those of groundwater samples. Because of the age and size of the two waste water treatment plants are significantly different, it was also observed that the isotope contents of plant B, younger age and smaller size, was relatively lower in 2H values and 3H activities compared to those of plant A. These phenomena have been used to identify the leaching from waste-water treatment plants of Bantar Gebang landfill to the underlying aquifer. During the dry season, it was observed that 2H values in leachate were generally higher than those in rainy season. This result might be due to the extensive methane production in the treatment plants. Conversely, 18O-shifting in leachate from local meteoric line indicated that the leachate had experienced evaporation. Buried luminescent paints in the landfill were most likely the source of high tritium activity in leachate. Based on the samples collected from the study area (mostly from dug or bore wells), it was found that the underlying aquifer especially shallow groundwater has been contaminated up to as high as 33% with leachate. (author)

  19. Concentration effects on laser-based δ18 O and δ2 H measurements and implications for the calibration of vapour measurements with liquid standards.

    Schmidt, Markus; Maseyk, Kadmiel; Lett, Céline; Biron, Philippe; Richard, Patricia; Bariac, Thierry; Seibt, Ulli

    2010-12-30

    Recently available isotope ratio infrared spectroscopy can directly measure the isotopic composition of atmospheric water vapour (δ(18) O, δ(2) H), overcoming one of the main limitations of isotope ratio mass spectrometry (IRMS) methods. Calibrating these gas-phase instruments requires the vapourisation of liquid standards since primary standards in principle are liquids. Here we test the viability of calibrating a wavelength-scanned cavity ring-down spectroscopy (CRDS) instrument with vapourised liquid standards. We also quantify the dependency of the measured isotope values on the water concentration for a range of isotopic compositions. In both liquid and vapour samples, we found an increase in δ(18) O and δ(2) H with water vapour concentration. For δ(18) O, the slope of this increase was similar for liquid and vapour, with a slight positive relationship with sample δ-value. For δ(2) H, we found diverging patterns for liquid and vapour samples, with no dependence on δ-value for vapour, but a decreasing slope for liquid samples. We also quantified tubing memory effects to step changes in isotopic composition, avoiding concurrent changes in the water vapour concentration. Dekabon tubing exhibited much stronger, concentration-dependent, memory effects for δ(2) H than stainless steel or perfluoroalkoxy (PFA) tubing. Direct vapour measurements with CRDS in a controlled experimental chamber agreed well with results obtained from vapour simultaneously collected in cold traps analysed by CRDS and IRMS. We conclude that vapour measurements can be calibrated reliably with liquid standards. We demonstrate how to take the concentration dependencies of the δ-values into account. Copyright © 2010 John Wiley & Sons, Ltd. PMID:21080508

  20. Use of the δ18O and δ15N of nitrate to determine sources of nitrate in early spring runoff in forested catchments

    Many upland catchments have increased nitrate and hydrogen ion concentrations in stream water during the early snowmelt period. The dominant source of this nitrate is not well known, but likely contributors include atmospheric deposition of nitrate and ammonium in the snowpack, and soil derived nitrate. Pilot studies initiated in three catchments during the 1994 snowmelt season show that analysis of both the δ18O and δ15N of nitrate provides excellent separation of nitrate sources. Almost all the stream samples have nitrate δ18O and δ15N values within the range of the pre-melt soil and stream waters, suggesting that atmospheric nitrate eluted from the 1994 snowpack is a minor source of nitrate in early streamflow. Therefore, the nitrate eluted from the 1994 snowpack appears to go into storage, and most of the nitrate in streamflow during the period of potential acidification was derived from pre-melt sources. The δ18O of pre-melt nitrate in soil and stream waters is intermediate between the compositions of atmospheric and solid derived nitrate, indicating a mixture of sources. The enriched composition of the pre-melt nitrate suggests that either atmospheric nitrate is actually a dominant source of nitrate to the catchment on a yearly basis, or that there is recharge of shallow storage by percolating snowmelt during midwinter thaws. In either case, the nitrate pulse in stream water during early melt appears to be largely derived from precipitation from previous months or years that is flushed from storage. (author). 12 refs, 2 figs

  1. Oxygen isotopes of Pacific seawater, 0-40 kyr, based on d18O and Mg/Ca of benthic and planktic foraminifera: relation to deglacial sealevel rise.

    Mix, A. C.; Klinkhammer, G. P.

    2007-12-01

    Combining high resolution (~200 year sample resolution) oxygen and carbon isotope measurements and Mg/Ca analyses in planktic (G. ruber and N. dutertrei) and benthic foraminifera (Uvigerina sp.; use of infaunal benthics minimizes likely CO3= effects) from the mid-depth eastern Pacific provides for detailed estimates of changing d18O of seawater over the past 40 kyr at ODP Site 1242. The key to this analysis is improved precision of the Mg/Ca analyses based on a new generation of high precision flow-through time-resolved analysis (FT-TRA) (e.g., average internal precision for Mg/Ca is now +/-0.005 benthic, and +/-0.015 planktic). This method is relatively insensitive to mild dissolution of heterogeneous shells, and thus requires no corrections for preservation. The change in seawater d18O (at 1364 m depth) between the Holocene and Last Glacial Maximum is 1.2 +/- 0.04 permil when averaged over the stages, consistent with pore-water diffusion estimates; however, millennial scale events (which the pore-water data cannot detect) bring the total range up to about 1.6 permil. Are such short-term events related to sealevel change, or do they reflect changing watermasses? Measurements of d13C data (C. wuellerstorfi), sensitive to modern subsurface watermass gradients, are not highly correlated to short- term changes in d18Oseawater suggesting a transient response to ice volume changes. Glacial weakening of AAIW (salty, high d18O, high d13C) relative to north Pacific watermasses (fresher, lower d18O, low d13C) suggest that the benthic d18Oseawater may underestimate total local changes related to ice volume (with a caveat regarding proper scaling of benthic Mg/Ca to temperature). Benthic d18Oseawater falls through the deglaciation in steps, starting at 18 cal ka, with maximum rates of change at 14-15 ka, and with secondary rapid steps at 16-17 ka and 10-11 kar. Planktic foraminifera yield smaller glacial-interglacial d18Oseawater values, with Holocene-to-LGM stage- average

  2. Particle–particle Tamm–Dancoff approximation and particle–particle random phase approximation calculations for 18O and 18F nuclei

    Alih Taqi Al-Bayati

    2013-02-01

    The nuclear structures of 18O and 18F nuclei are studied using particle–particle Tamm–Dancoff approximation (pp TDA) and particle–particle random phase approximation (pp RPA). All possible single-particle states of the allowed angular momenta are considered in the 0p and 1s–0d shells. The Hamiltonian is diagonalized in the presence of Warburton and Brown interactions. The results containing energy-level schemes and transition strength (2) are compared with the available experimental data.

  3. Comparing three methods of NEE-flux partitioning from the same grassland ecosystem: the 13C, 18O isotope approach and using simulated Ecosystem respiration

    Siegwolf, R.; Bantelmann, E.; Saurer, M.; Eugster, W.; Buchmann, N.

    2007-12-01

    As a change in the global climate occurs with increasing temperatures, the Carbon exchange processes of terrestrial ecosystems will change as well. However, it is difficult to quantify the degree to what ecosystem respiration will change relative to the CO2 uptake by photosynthesis. To estimate the carbon sequestration potential of terrestrial vegetation cover it is essential to know both fluxes: ecosystem respiration and the carbon uptake by the vegetation cover. Therefore the net ecosystem exchange of CO2 (NEE) was measured with the eddy covariance method and separated into assimilation and respiration flux. We applied three different approaches, 1) the conventional method, applying the nighttime relationship between soil temperature and NEE for calculating the respiration flux during the day, 2) the use of stable carbon and 3) oxygen isotopes. We compared the results of the three partitioning exercises for a temperate grassland ecosystem in the pre-Alps of Switzerland for four days in June 2004. The assimilation flux derived with the conventional NEE partitioning approach, was best represented at low PAR and low temperatures, in the morning between 5 and 9 am. With increasing temperature and PAR the assimilation for the whole canopy was underestimated. For partitioning NEE via 18O approach, correlations of temperature and radiation with assimilation and respiration flux were significantly higher for the partitioning approach with 18O than for the 13C NEE partitioning. A sensitivity analysis showed the importance of an accurate determination of the equilibrium term θ between CO2 and leaf water δ18O for the NEE partitioning with 18O. For using 13C to partition NEE, the correct magnitude of the 13C fractionation and for the respiration term is essential. The analysis of the data showed that for low light and low morning temperatures the conventional method delivers reasonably good results. When the temperatures exceeded 21°C the isotope approach provided the

  4. Multipolarity analysis for {sup 14}C high-energy resonance populated by ({sup 18}O,{sup 16}O) two-neutron transfer reaction

    Carbone, D., E-mail: carboned@lns.infn.it; Cavallaro, M.; Bondì, M.; Agodi, C.; Cunsolo, A. [INFN-Laboratori Nazionali del Sud, Catania (Italy); Cappuzzello, F. [INFN-Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Catania (Italy); Azaiez, F.; Franchoo, S.; Khan, E. [Institut de Physique Nucleaire, Universitè Paris-Sud, Orsay (France); Bonaccorso, A. [INFN-Sezione di Pisa, Pisa (Italy); Fortunato, L. [Dipartimento di Fisica e Astronomia, Università di Padova, Padova (Italy); INFN-Sezione di Padova, Padova (Italy); Foti, A. [Dipartimento di Fisica e Astronomia, Università di Catania, Catania (Italy); INFN-Sezione di Catania, Catania (Italy); Linares, R.; Lubian, J. [Instituto de Fisica, Universidade Federal Fluminense, Niteroi (Brazil); Scarpaci, J. A. [Centre de Sciences Nucleaires et de Sciences de Matieres, Universitè Paris-Sud, Orsay (France); Vitturi, A. [INFN-Sezione di Padova, Padova (Italy); INFN-Sezione di Catania, Catania (Italy)

    2015-10-15

    The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C reaction at 84 MeV incident energy has been explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed at 16.9 MeV. A multipolarity analysis of the cross section angular distribution indicates an L = 0 character for such a transition.

  5. Identifying residence times and streamflow generation processes using δ18O and δ2H in meso-scale catchments in the Abay/Upper Blue Nile, Ethiopia

    Teklaeb, S.; Wenninger, J.W.; Uhlenbrook, S.

    2013-01-01

    Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin. Stable isotope composition in precipitation, spring water and streamflow were analyzed (i) to characterize the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time o...

  6. New High-Precision Measurement of the Reaction Rate of the 18O(p,alpha)15N Reaction via THM

    La Cognata, M; Mukhamedzhanov, A M; Irgaziev, B; Tribble, R E; Banu, A; Cherubini, S; Coc, A; Crucilla, V; Goldberg, V Z; Gulino, M; Kiss, G G; Lamia, L; Chengbo, L; Mrazek, J; Pizzone, R G; Puglia, S M R; Rapisarda, G G; Romano, S; Sergi, M L; Tabacaru, G; Trache, L; Trzaska, W; Tumino, A

    2009-01-01

    The 18O(p,alpha)15N reaction rate has been extracted by means of the Trojan-Horse method. For the first time the contribution of the 20-keV peak has been directly evaluated, giving a value about 35% larger than previously estimated. The present approach has allowed to improve the accuracy of a factor 8.5, as it is based on the measured strength instead of educated guesses or spectroscopic measurements. The contribution of the 90-keV resonance has been determined as well, which turned out to be of negligible importance to astrophysics.

  7. Synthesis of LiMn2O4 and LiCr0.2Mn1.8O4 powders by modified Pechini process

    Alexandre Urbano

    2009-03-01

    Full Text Available LiMn2O4 and LiCr0.2Mn1.8O4 powders were synthesized by Pechini process, modified in order to reduce the number of steps and to work at temperatures below or equal to 400oC. Both phases crystallize in the same spinel structure with lattice constants of 8.21 and 8.22 Å respectively. Although the annealing temperature was low, the cristallinity is good and no residual amounts of organic material were detected.

  8. Multifragment emission in the interaction of 86 MeV/μ 18O-ions with 197Au, 184W, and 106Ag

    Thin targets of 197Au, 184W, and 106Ag were vacuum deposited on Muscovite mica, CR-39, Makrofol-E, and phosphate glass track detectors. The 'target-detector' assemblies were then exposed perpendicularly to 86 MeV/μ 18O ions at CERN-SC. The exposed detectors were etched in appropriate etchants for various time intervals. Correlated reaction products were scanned in order to obtain multiprong events with different multiplicities. Multiplicity-distributions, fission-and total-reaction cross-sections have been determined. (author)

  9. Extracting the cross section angular distributions for 15C high-energy resonance excited via the (18O,16O two-neutron transfer reaction

    Carbone D.

    2016-01-01

    Full Text Available The 13C(18O,16O15C reaction has been studied at 84 MeV incident energy. The ejectiles have been momentum analized by the MAGNEX spectrometer and 15C excitation energy spectra have been obtained up to about 20 MeV. In the region above the two-neutron separation energy, a bump has been observed at 13.7 MeV. The extracted cross section angular distribution for this structure, obtained by using different models for background, displays a clear oscillating pattern, typical of resonant state of the residual nucleus.

  10. Variability of {sup 10}Be and {delta}{sup 18}O in snow pits from Greenland and a surface traverse from Antarctica

    Berggren, A.-M. [Dept. of Earth Sciences, Uppsala University, Villav. 16, 752 36 Uppsala (Sweden); Aldahan, A., E-mail: ala.aldahan@geo.uu.se [Dept. of Earth Sciences, Uppsala University, Villav. 16, 752 36 Uppsala (Sweden); Dept. of Geology, United Arab Emirates University, P.O. Box 17551 Al Ain (United Arab Emirates); Possnert, G. [Tandem Laboratory, Uppsala University, P.O. Box 529, 751 20 Uppsala (Sweden); Hansson, M. [Dept. of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm (Sweden); Steen-Larsen, H.C. [Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej, 30,2100 Copenhagen (Denmark); Sturevik Storm, A. [Dept. of Earth Sciences, Uppsala University, Villav. 16, 752 36 Uppsala (Sweden); Moerth, C.-M. [Dept. of Geology and Geochemistry, Stockholm University, 106 91 Stockholm (Sweden); Murad, A. [Dept. of Geology, United Arab Emirates University, P.O. Box 17551 Al Ain (United Arab Emirates)

    2013-01-15

    To examine temporal variability of {sup 10}Be in glacial ice, we sampled snow to a depth of 160 cm at the NEEM (North Greenland Eemian Ice Drilling) drilling site in Greenland. The samples span three years between the summers of 2006 and 2009. At the same time, spatial variability of {sup 10}Be in glacial ice was explored through collection of the upper {approx}5 cm of surface snow in Antarctica during part of the Swedish-Japanese traverse from Svea to Syowa station during the austral summer in 2007-2008. The results of the Greenlandic {sup 10}Be snow suggested variable concentrations that apparently do not clearly reflect the seasonal change as indicated by the {delta}{sup 18}O data. The {sup 10}Be concentration variability most likely reflects also effects of aerosol loading and deposition pathways, possibly in combination with post-depositional processes. The Antarctic traverse data expose a negative correlation between {sup 10}Be and {delta}{sup 18}O, while there are weaker but still significant correlations to altitude and distance to the coast (approximated by the distance to the 70th latitude). These relationships indicate that geographical factors, mainly the proximity to the coast, may strongly affect {sup 10}Be concentrations in snow in Queen Maud Land, Antarctica.

  11. Assessing biodegradation of chlorinated aliphatic hydrocarbons in a river sediment by conservative and reactive isotope tracers (2H, 18O, 13C)

    Full text: This study is part of the joint project SEDBARCAH, which investigates the intrinsic capacity of microbial communities in eutrophic river sediments as natural biobarriers against the release of chlorinated aliphatic hydrocarbons (CAHs) from polluted ground water into surface water. The study site is located in an industrial area in Vilvoorde (Belgium) and characterized by heavily CAH-contaminated groundwater, which infiltrates the sediments of the eutrophic river Zenne. The stable isotopic compositions (δ2H, δ18O) of ground water, interstitial water, and Zenne surface water were used as conservative tracers to distinguish between river sediment zones, which are characterized by (i) ground water influx and exfiltration and (ii) river water infiltration and mixing between ground and surface water. Interstitial water was sampled in 3 longitudinal river sediment profiles in up to 3 depths in a 45 m long section of the Zenne. The δ2H- and δ18O-data show that ground water and Zenne surface water are isotopically clearly distinct. Interstitial water mostly exhibits δ2H- and δ18O-values identical or close to ground water, indicating influx of ground water into the sediments and exfiltration into the surface water at these positions. However, at several sampling positions and depths δ2H- and δ18O-values of interstitial water approaches or attains those of Zenne surface water. This testifies to surface water infiltration into the river sediments and mixing with ascending groundwater. These findings thus reflect the existence of small- to mid-scale hydraulic heterogeneities in the sediment and/or differences in the basal river flow velocities, which led to the establishment of zones of rapid as well as slow or even suppressed discharge of CAH-contaminated ground water into the Zenne surface water. At present, the CAH-pollution in the ground and interstitial water consists of vinyl chloride (VC), cis-1,2-dichloroethene (cis-DCE), and 1,1-dichloroethane (1

  12. Investigation on effects of bottle material on water evaporation and isotopic changes in δ2H and δ18O during sample storage

    The interpretation of results of water stable-isotope analyses is less reliable if the water storage conditions are not suitable. One very important aspect in this respect is the type and material of the sample bottles used for sampling and storage. The IAEA has a long experience with projects carried out worldwide within its Technical Cooperation (TC) activities and within the Global Network of Isotopes in Precipitation (GNIP). For use within its GNIP activities the IAEA recommends and supplies coloured glass bottles with proper seal and closure for mid- and long-term storage of water samples. However, because of the obvious restrictions of glass (breakable, heavy in transport), and because in most other cases the analysis commences relatively soon after sampling, different types of high-density polyethylene (HDPE) bottles with inner seals and proper caps were found to be adequate. The IAEA has used HDPE bottles for many years now and supplies them to TC counterparts. In the past, and occasionally also to date, water samples are also taken and shipped to IAEA in locally available, various types of containers and bottles. A survey recently revealed around 60 different types of containers (many of which being obviously inadequate), that were used to send samples to the IAEA Isotope Hydrology Laboratory (IHL) in the past decades. Requests were made by local counterparts to investigate some locally and globally available sample bottles on their suitability for sampling, shipping and storing samples for stable isotopes. These considerations lead to a series of tests on sample bottles in the IAEA-IHL. The following tests were performed: 1. The δ18O composition was re-measured in old samples, stored at the IAEA-IHL for 2 - 7 years 2. Three of each kind of old sample bottles were emptied, dried and filled with a well known water, fairly different in isotopic composition from Vienna rainwater and corresponding air moisture (distilled lake surface water, δ2H =-38.7 per

  13. Gas emissions in Planck cold dust clumps---A Survey of the J=1-0 Transitions of $^{12}$CO, $^{13}$CO, and C$^{18}$O

    Wu, Yuefang; Meng, Fanyi; Li, Di; Qin, Sheng-Li; Ju, Bing-Gang

    2012-01-01

    A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC) in the J=1-0 transitions of $^{12}$CO, $^{13}$CO and C$^{18}$O has been carried out using the PMO 13.7 m telescope. 673 clumps were detected with the $^{12}$CO and $^{13}$CO, and 68% of the samples have C$^{18}$O emission. Additional velocity components were also identified.A close consistency of the three line peak velocities was revealed for the first time. Kinematic distances are given out for all the velocity components and half of the clumps are located within 0.5 and 1.5 kpc. Excitation temperatures range from 4 to 27 K, slightly larger than those of $T_d$. Line width analysis shows that the majority of ECC clumps are low mass clumps. Column densities N$_{H_{2}}$ span from 10$^{20}$ to 4.5$\\times10^{22}$ cm$^{-2}$ with an average value of (4.4$\\pm$3.6)$\\times10^{21}$ cm$^{-2}$. N$_{H_{2}}$ cumulative fraction distribution deviates from the lognormal distribution, which is attributed to optical depth. The average abundance rati...

  14. New method to measure oxygen isotopic concentration ratios 18O/16O by gamma-activation analysis, especially in biological media

    Two photonuclear reactions were used for this isotopic analysis: 16O(γ,n)15O (threshold energy 15.7 MeV) and 18O(γ,p)17N (threshold energy 16.3 MeV). 15O is a pure β+ emitter of half-life 2.03 minutes, whereas 17N presents a 4.2 second neutron emission. A scintillation probe equipped with a sodium iodide crystal detects the 15O positron annihilation γ-rays. The 17N neutron activity is recorded with BF3 type counters. The potentialities of this new oxygen isotope analysis method using an electron accelerator, are described. Detection limit of 0.1 μg 18O is easily attainable. The equipment designed and built to industrialize this technique is described. The measurement system is connected by a fast pneumatic circuit to the irradiation device set up at the outlet of the accelerator. The flow-sheet of the apparatus is shown. A central electronic control unit commands, according to a pre-set time table, the linear accelerator, the sample loader, the pneumatic circuits and the counting instruments. It allows a hundred samples to be analysed automatically, the accelerator, detection instruments and pneumatic transfer circuits being controlled by a logic system linked to an electronic chronometer. (T.G.)

  15. Methodology to Extract Water from Soil and Plants for Stable Isotope Ratio (18O/16O and 2H/1H) Analyses by CRDS

    As part of the activities supporting the IAEA scientific water forum held from 20-21 September 2011, the SWMCN Subprogramme organized a 4 day display from 12-15 September to raise awareness of the importance of using nuclear methodologies to address water scarcity and saving water in agriculture. The SWMCN Laboratory in the FAO/IAEA laboratories at Seibersdorf exhibited a vacuum distillation technique, which has been developed to extract water from soil and plant for isotopic analysis by using cavity ring-down spectroscopy (CRDS). This technique greatly simplifies the previously employed low temperature freezing method. In the past, isotopic measurements of water in soil and plant material could only be achieved by a tedious and complicated process involving trapping by low temperature freezing and subsequent analysis by IRMS. During the exhibition, the SWMCN Laboratory demonstrated how water from soil (sand and clay) over a range of moisture levels from field capacity to permanent wilting point and plant samples could be easily extracted and analysed for 18O and 2H using CRDS. Accurate and reproducible results have been obtained for both sand and clay soils (with precision of the CRDS being 18O and 2H), giving >99% recovery of the soil and plant water. The use of CRDS and the improved water extraction technique greatly enhanced and simplified analytical capabilities to investigate water use efficiency, something that could only be dreamt about a few years ago.

  16. Precipitation origin and evaporation of lakes in semi-arid Patagonia (Argentina) inferred from stable isotopes ( δ18O, δ2H)

    Mayr, Christoph; Lücke, Andreas; Stichler, Willibald; Trimborn, Peter; Ercolano, Bettina; Oliva, Gabriel; Ohlendorf, Christian; Soto, Julio; Fey, Michael; Haberzettl, Torsten; Janssen, Stephanie; Schäbitz, Frank; Schleser, Gerhard H.; Wille, Michael; Zolitschka, Bernd

    2007-02-01

    Stable isotope approaches are often used for estimating water balances of lakes. Such studies require regional background information about hydrogen and oxygen isotope variability of lakes and their potential inflows. Here, a stable isotope database ( δ2H and δ18O) is presented for estimating evaporation to inflow ratios ( E/ I) of lakes in semi-arid southern Patagonia. Water samples of 23 lakes and ponds located in the Patagonian steppe at about 52°S were sampled during three subsequent austral summers. Two deep crater lakes, Laguna Azul and Laguna Potrok Aike, were studied in more detail during a two-years monitoring. Furthermore, precipitation, groundwater and atmospheric water vapor were sampled for isotope analyses. Presented data imply that the isotopic composition of rainfall in southeastern Patagonia is predominantly determined by precipitation amount and moisture source area. For the investigated area, the first meteoric water and evaporation lines in δ2H vs. δ18O space are presented. The database was further used to estimate the water balances of the two crater lakes, Laguna Azul and Laguna Potrok Aike, which are in the focus of recent paleoclimatic investigations. According to that approach about 50% and 60%, respectively, of the water entering Laguna Azul and Laguna Potrok Aike via surface and subsurface inflow evaporates. These results testify a considerable flow of lake waters into the groundwater.

  17. Herschel/HIFI search for H2-17O and H2-18O in IRC+10216: constraints on models for the origin of water vapor

    Neufeld, David A; Agúndez, Marcelino; González-Alfonso, Eduardo; Decin, Leen; Daniel, Fabien; Cernicharo, José; Melnick, Gary J; Schmidt, Miroslaw; Szczerba, Ryszard

    2013-01-01

    We report the results of a sensitive search for the minor isotopologues of water, H2-17O and H2-18O, toward the carbon-rich AGB star IRC+10216 (a.k.a. CW Leonis) using the HIFI instrument on the Herschel Space Observatory. This search was motivated by the fact that any detection of isotopic enhancement in the H2-17O and H2-18O abundances would have strongly implicated CO photodissociation as the source of the atomic oxygen needed to produce water in a carbon-rich circumstellar envelope. Our observations place an upper limit of 1/470 on the H2-17O/H2-16O abundance ratio. Given the isotopic 17O/16O ratio of 1/840 inferred previously for the photosphere of IRC+10216, this result places an upper limit of a factor 1.8 on the extent of any isotope-selective enhancement of H2-17O in the circumstellar material, and provides an important constraint on any model that invokes CO photodissociation as the source of O for H2O production. In the context of the clumpy photodissociation model proposed previously for the origi...

  18. Estimating the regional climate signal in a late Pleistocene and early Holocene lake-sediment δ18O record from Vermont, USA.

    Mandl, Maximilian Benedict; Shuman, Bryan Nolan; Marsicek, Jeremiah; Grigg, Laurie

    2016-07-01

    We present a new oxygen isotope (δ18O) record from carbonate-rich lake sediments from central Vermont. The record from Twin Ponds spans from 13.5 cal ka BP (1950 AD) to present, but contains a 6 ka long hiatus starting shortly after 7.5 cal ka BP. We compare the record for ca. 13.5-7.5 cal ka BP with published δ18O data from the region after using a Bayesian approach to produce many possible chronologies for each site. Principal component analysis then identified chronologically-robust, multi-site oxygen isotope signals, including negative values during the Younger Dryas, but no significant deviations from the early Holocene mean of the regional records. However, differences among sites indicate significant trends that likely relate to interacting changes in the regional gradients of seasonal temperatures and precipitation as well as moisture sources, moisture pathways, and aridity that were controlled by large-scale climatic controls such as insolation, the progressive decline of the Laurentide Ice Sheet, and changes in oceanic circulation. Centennial shifts punctuate these trends at ca. 9.3 and 8.2 cal ka BP, and reveal that the local character of these short-lived features requires a detailed understanding of lake hydrology and regional isotopic gradients to yield reliable information for regional climate reconstructions.

  19. Using Multi-Species Foraminiferal δ18O to Reconstruct Hydrologic Changes in the Gulf of Panama From LGM to Present

    Benway, H. M.; Mix, A. C.

    2002-12-01

    Currently, an excess in precipitation minus evaporation (P-E) maintains a low-salinity surface layer and a shallow pycnocline in the Gulf of Panama. In contrast, the Caribbean has high salinity due to high evaporation relative to precipitation. The strong salinity gradient between these two regions is sustained by northeasterly trade winds, which carry evaporated moisture from the Caribbean over the Panama Isthmus and into the Gulf of Panama, where high SSTs attract the moisture-laden air masses. This leads to atmospheric convection and heavy rainfall on the Pacific side of the Isthmus in the Gulf of Panama. Since the majority of the rainfall in this region originates as water vapor in the Caribbean, changes in vapor transport can be estimated by changes in upper ocean structure in the Gulf of Panama. A multi-species approach is used in a Panama Basin sediment core to reconstruct changes in cross-isthmus vapor transport from LGM to present. We measure δ18O in two species of planktonic foraminifera, one that lives at the surface and one that lives at the base of the pycnocline, in order to estimate the isotopic contrast across the pycnocline, which is directly related to net precipitation in the Gulf of Panama (i.e., an increase in δ18O contrast between the sea surface and the base of the pycnocline is associated with an increase in P-E).

  20. Use of Isotope Ratio Mass Spectrometry (IRMS) Determination ((18)O/(16)O) to Assess the Local Origin of Fish and Asparagus in Western Switzerland.

    Rossier, Joël S; Maury, Valérie; de Voogd, Blaise; Pfammatter, Elmar

    2014-10-01

    Here we present the use of isotope ratio mass spectrometry (IRMS) for the detection of mislabelling of food produced in Switzerland. The system is based on the analysis of the oxygen isotope distribution in water (δ(18)O). Depending on the location on the earth, lake or groundwater has a specific isotopic distribution, which can serve as a fingerprint in order to verify whether a product has grown by means of the corresponding water. This report presents specifically the IRMS technique and the results obtained in the origin detection of fish grown in selected Swiss lakes as well as asparagus grown in Valais ground. Strengths and limitations of the method are presented for both cited products; on one hand, the technique is relatively universal for any product which contains significant water but on the other hand, it necessitates a rather heavy workload to build up a database of water δ(18)O values of products of different origins. This analytical tool is part of the concept of combating fraud currently in use in Switzerland. PMID:25437160

  1. Anomalous flow below 2700 m in the EPICA Dome C ice core detected using δ18O of atmospheric oxygen measurements

    A. Tisserand

    2007-01-01

    Full Text Available While there are no indications of mixing back to 800 000 years in the EPICA Dome C ice core record, comparison with marine sediment records shows significant differences in the timing and duration of events prior to stage 11 (~430 ka, thousand of years before 1950. A relationship between the isotopic composition of atmospheric oxygen (δ18O of O2, noted δ18Oatm and daily northern hemisphere summer insolation has been observed for the youngest four climate cycles. Here we use this relationship with new δ18O of O2 measurements to show that anomalous flow in the bottom 500 m of the core distorts the duration of events by up to a factor of 2. By tuning δ18Oatm to orbital precession we derive a corrected thinning function and present a revised age scale for the interval corresponding to Marine Isotope Stages 11–20 in the EPICA Dome C ice core. Uncertainty in the phasing of δ18Oatm with respect to insolation variations in the precession band limits the accuracy of this new agescale to ±6 kyr (thousand of years. The previously reported ~30 kyr duration of interglacial stage 11 is unchanged. In contrast, the duration of stage 15.1 is reduced by a factor of 2, from 31 to 16 kyr.

  2. Physiological and isotopic (delta(13)C and delta(18)O) responses of three tropical tree species to water and nutrient availability.

    Cernusak, Lucas A; Winter, Klaus; Turner, Benjamin L

    2009-10-01

    Water-use efficiency and stable isotope composition were studied in three tropical tree species. Seedlings of Tectona grandis, Swietenia macrophylla and Platymiscium pinnatum were grown at either high or low water supply, and with or without added fertilizer. These three species previously exhibited low, intermediate and high whole-plant water-use efficiency (TE) when grown at high water supply in unfertilized soil. Responses of TE to water and nutrient availability varied among species. The TE was calculated as experiment-long dry matter production divided by cumulative water use. Species-specific offsets were observed in relationships between TE and whole-plant (13)C discrimination (Delta(13)C(p)). These offsets could be attributed to a breakdown in the relationship between Delta(13)C(p) and the ratio of intercellular to ambient CO(2) partial pressures (c(i)/c(a)) in P. pinnatum, and to variation among species in the leaf-to-air vapour pressure difference (v). Thus, a plot of v.TE against c(i)/c(a) showed a general relationship among species. Relationships between delta(18)O of stem dry matter and stomatal conductance ranged from strongly negative for S. macrophylla to no relationship for T. grandis. Results suggest inter-specific variation among tropical tree species in relationships between stable isotope ratios (delta(13)C and delta(18)O) and the gas exchange processes thought to affect them. PMID:19558409

  3. A megasplice of globally distributed benthic δ18O records exposes the different astronomical rhythms of the last 35 million years.

    De Vleeschouwer, David; Vahlenkamp, Maximilian; Crucifix, Michel; Pälike, Heiko

    2016-04-01

    Compilations of worldwide benthic δ18O records (e.g. Cramer et al., 2009; Zachos et al., 2001; Zachos et al., 2008) led to a significant improvement of our understanding of changing ocean circulation characteristics in the Cenozoic. However, in these compilations, different isotopic records are accumulated and individual astronomical cycles are not always clearly recognizable. Here, we present a benthic δ18O megasplice for the last 35 Ma that results from the splicing of a dozen globally distributed high-resolution isotope records (>11000 measurements). We carefully correlated these isotope records in their overlapping parts, and slightly revised the original astronomical age models where necessary. The result is a megasplice in which individual astronomical cycles are clearly delineated throughout the last 35 Ma. Benthic δ18O records from the deep ocean can be regarded as resembling globally averaged temperature and ice-volume conditions. Nevertheless, an important disadvantage of the megasplice consists of the fact that data from single sites do not reflect whole ocean conditions. We account for possible local effects by presenting different versions of the megasplice, each version consisting of a different combination of records. Subsequently, the imprint of astronomical climate forcing in the megasplice is displayed in a novel way. We display the response of benthic δ18O to obliquity and eccentricity-modulated precession for 800-kyr wide time-windows. The δ18O response in function of obliquity and e*sin(ω) allows for an assessment of the relative strength of obliquity and precession. A similar display in function of e*sin(ω) and e*cos(ω) should be read as a polar plot of which the azimuth represents the longitude of the perihelion and the distance from the pole represents eccentricity. The month during which the Earth reaches perihelion is indicated at the corresponding azimuth. This novel way of visualizing the astronomical imprint allows us to

  4. Effect of temperature on the oxygen isotope composition of carbon dioxide (δ18O) prepared from carbonate minerals by reaction with polyphosphoric acid: An example of the rhombohedral CaCO 3-MgCO 3 group minerals

    Crowley, Stephen F.

    2010-11-01

    Measurement of the ratio of 18O to 16O in CO 2(δ18O) produced from rhombohedral carbonate minerals in the compositional range CaCO 3-MgCO 3 by reaction with polyphosphoric acid (PPA), at temperatures of between 25 and 110 °C, shows that values of δ18O are linearly correlated ( r o > 0.99) with the reciprocal of absolute reaction temperature (K/ T). This observation is consistent with earlier studies documenting the effect of temperature on the kinetic fractionation of oxygen isotopes between parent carbonate and product CO 2 and H 2O during acid decomposition. However, analysis of the resultant data reveals: (1) a progressive increase in dδ18O/dT-1 with increasing Mg content, and (2) a significant variation in dδ18O/dT-1 between individual samples of carbonate of identical lattice symmetry and similar chemical composition. The overall increase in gradient with increasing Mg content is assumed to reflect cation radius dependent factors that control the bonding environment at the interface between the metal cation exposed at the surface of the reacting carbonate solid and a H 2CO 3 transitional species during disproportionation of H 2CO 3 to CO 2 and H 2O ("cluster model" of Guo et al., 2009). Phase-specific variations in dδ18O/dT-1 might result from differences in lattice structure variables (e.g., degree of lattice distortion, extent of positional disorder, and non-ideal mixing of substituent cations where carbonates depart from end-member compositions). Lattice structure variables may be dependent on geochemical conditions pertaining at the time of carbonate precipitation (e.g., biosynthetic versus inorganic precipitates) and suggests that dδ18O/dT-1 has the potential to vary, within limits, in response to both the chemical composition and structure of each carbonate sample. Because the oxygen isotope composition of carbonate minerals (δ18O) measured on the VPDB scale is defined by the oxygen isotope composition of CO 2 prepared from NBS19 (calcite) by

  5. Measurements of the 24Mg(d,p0,1,2,3,4) and natMg(d,d0) reactions cross sections in the energy range of 1.2-2 MeV for NRA and EBS applications

    Rafi-kheiri, H.; Kakuee, O.; Lamehi-Rachti, M.

    2016-04-01

    Differential cross sections of the 24Mg(d,p0,1,2,3,4) reactions were obtained in the range Ed,lab = 1.2-2 MeV and at the scattering angles of 90°, 135°, 150° and 165° using a thin Mg target having thickness of 76.7 ± 3.1 μg/cm2. The cross section values were determined with an average energy step of ∼25 keV while the detailed measurements were carried out with an energy step of ∼5 keV around the resonance peaks. Elastic scattering data for three steep backward angles (135°, 150° and 165°) were also studied for the same incident deuteron energy range and steps. The results were compared with those of the previous studies. Moreover, the validity of the measured data has been benchmarked using a thick Mg target at two deuteron beam energies of 1.7 and 2 MeV.

  6. Application of stable isotopes (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4,} δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}) to determine natural background and contamination sources in the Guadalhorce River Basin (southern Spain)

    Urresti-Estala, Begoña, E-mail: b.urresti@uma.es [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain); Vadillo-Pérez, Iñaki; Jiménez-Gavilán, Pablo [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain); Soler, Albert [Grup de Mineralogia Aplicada i Medi Ambient, Fac. Geologia, Universitat de Barcelona, Barcelona (Spain); Sánchez-García, Damián; Carrasco-Cantos, Francisco [Universidad de Málaga, Facultad de Ciencias, Grupo de Geodinámica Externa, Campus de Teatinos s/n, 29071 Málaga (Spain)

    2015-02-15

    The integrated use of isotopes (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4,} δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}), taking into account existing hydrogeological knowledge of the study area (mainly hydrochemical), was applied in the Guadalhorce River Basin (southern Spain) to characterise SO{sub 4}{sup 2−} and NO{sub 3}{sup −} sources, and to quantify natural background levels (NBLs) in groundwater bodies. According to Water Framework Directive 2000/60/EC and, more recently, Groundwater Directive 2006/118/EC, it is important to determine NBLs, as their correct assessment is the first, essential step to characterising groundwater bodies, establishing threshold values, assessing chemical status and identifying trends in pollutant concentrations. In many cases, NBLs are high for some parameters and types of groundwater, making it difficult to distinguish clearly between factors of natural or human origin. The main advantages of using stable isotopes in a complex area like the Guadalhorce River Basin that exhibits widely varying hydrogeological and hydrochemical conditions and longstanding anthropogenic influences (mainly agriculture, but also many others) is accurate determination of pollution sources and precise quantification of NBLs. Since chemical analyses only provides the concentration of pollutants in water and not the source, three isotopic sampling campaigns for sulphates (δ{sup 34}S-SO{sub 4}, δ{sup 18}O-SO{sub 4}) were carried out, in 2006, 2007 and 2012, and another one was conducted for nitrates (δ{sup 15}N-NO{sub 3}, δ{sup 18}O-NO{sub 3}), in 2009, in groundwater bodies in order to trace the origins of each pollutant. The present study identified different pollution sources of dissolved NO{sub 3}{sup −} in groundwater using an isotopic composition and quantified the percentage of natural (lithology, chemical and biological processes) and anthropogenic (fertilisers, manure and sewage) SO{sub 4}{sup 2−} and matched a concentration

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

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

    2009-03-01

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

  8. Stable isotope composition of inorganic carbonates from Lake Abiyata (Ethiopia): Attempt of reconstructing δ18O palaeohydrological changes during the Holocene

    Due to the sensitivity of its regional climate to the African monsoon seasonal shifting, Ethiopia has been designated as a key site for palaeoenvironmental reconstructions mainly within the IGBP-PAGES-PEPIII programme. Under the French-Ethiopian ERICA project, we focused on Lake Abiyata located in the Ziway-Shala basin (Central Ethiopia) which has experienced several lacustrine highstands during the Late Pleistocene and Holocene. At present, Lake Abiyata is a closed lake with a very flat catchment area, and corresponds to a half, deep graben infilled by 600-m of sedimentary deposits. In 1995, a 12.6-m-long sequence ABII was cored in Lake Abiyata. A reliable 14C-AMS chronology was defined on both organic matter and inorganic carbonates. Both the modern hydrologeological and geochemical balances of the 'groundwater-lake' system indicate that (i) carbonate cristallization mainly occurs at the water-sediment interface via the mixing of lake water and 14C-depleted groundwaters, and that (ii) modern algae form in equilibrium with the atmospheric reservoir. Phytoplankton is thus considered as an authigenic material, and Core ABII has registered 13,500 cal. yr B.P. of environmental history. The evidence of calcite precipitation at the water-sediment interface calls into question the direct palaeoclimatic reconstruction based on inorganic carbonates. Since the evolution of isotopic contents of carbonates might be linked to the variable proportion of the 'lake/groundwater' end-members in the mixing, calculations based on isotopic mass balance models may allow for the reconstruction of δ18O composition of the lake water. Two major changes can be highlighted: (i) the ∼12,000-5500 cal. yr B.P. period is associated to low 18O contents of lake water, and corresponds to an open hydrological system, with a high lacustrine phytoplanktonic productivity, and (ii) from ∼5500 cal. yr B.P. to Present, regressive conditions are suggested by the δ18O enrichment of the lake water

  9. 2H NMR and 13C-IRMS analyses of acetic acid from vinegar, 18O-IRMS analysis of water in vinegar: International collaborative study report

    An international collaborative study of isotopic methods applied to control the authenticity of vinegar was organized in order to support the recognition of these procedures as official methods. The determination of the 2H/1H ratio of the methyl site of acetic acid by SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and the determination of the 13C/12C ratio, by IRMS (isotope ratio mass spectrometry) provide complementary information to characterize the botanical origin of acetic acid and to detect adulterations of vinegar using synthetic acetic acid. Both methods use the same initial steps to recover pure acetic acid from vinegar. In the case of wine vinegar, the determination of the 18O/16O ratio of water by IRMS allows to differentiate wine vinegar from vinegars made from dried grapes. The same set of vinegar samples was used to validate these three determinations. The precision parameters of the method for measuring δ13C (carbon isotopic deviation) were found to be similar to the values previously obtained for similar methods applied to wine ethanol or sugars extracted from fruit juices: the average repeatability (r) was 0.45 per mille , and the average reproducibility (R) was 0.91 per mille . As expected from previous in-house study of the uncertainties, the precision parameters of the method for measuring the 2H/1H ratio of the methyl site were found to be slightly higher than the values previously obtained for similar methods applied to wine ethanol or fermentation ethanol in fruit juices: the average repeatability was 1.34 ppm, and the average reproducibility was 1.62 ppm. This precision is still significantly smaller than the differences between various acetic acid sources (δ13C and δ18O) and allows a satisfactory discrimination of vinegar types. The precision parameters of the method for measuring δ18O were found to be similar to the values previously obtained for other methods applied to wine and fruit juices: the

  10. Measurements of tritium and 14C production cross sections for 14.7-MeV neutrons on 17O and 18O

    A first generation deuterium-tritium (D-T) fusion reactor such as the International Thermonuclear Experimental Reactor has the nominal fusion power of 1,000 MW, which corresponds to a total output of ∼ 3 x 1020 14-MeV n/s. In contemporary designs of these fusion reactors, high-purity light water (H2O) is potentially used as a coolant. Hence, the cooling water is subject to 14-MeV neutron irradiation. The predominant neutron energies are above the thresholds for many reactions that are not normally significant in fission reactor analysis. Therefore, consideration of water activation with 14-MeV neutrons is important from the viewpoint of fusion reactor safety and waste management of long-lived isotopes such as 14C and tritium. Here, samples of water isotopically enriched in 17O, 18O, and 2H along with natural water were bombarded by neutrons from the intense deuterium-tritium source provided by the Fusion Neutron Source facility. After irradiation, the accumulated concentrations of 3H and 14C activities were determined by the liquid scintillation method. Special attention was paid to 14C losses in the gas phase during irradiation and preparation of scintillation counting samples. Cross sections for the 17O(n,α)14C, 18O(n,n'α)14C, 17O(n,t)15N, and 18O(n,t)16N reactions at 14.7 MeV have been measured for the first time. The following values have been obtained for these reactions: 18 ± 3.3, 35.4 ± 6.5, 0.82 ± 0.15, and 26.8 ± 4.9 mb, respectively, relative to the 93Nb(n,2n)92mNb standard reaction cross section of 460 mb. A study of the systematics of (n,t) reactions at 14.7 MeV on light nuclei (atomic number Z < 10) has been carried out. The experimental cross-section values are also compared with data in the comprehensive activation libraries

  11. In situ unsaturated zone water stable isotope (2H and 18O) measurements in semi-arid environments: a soil water balance

    Gaj, Marcel; Beyer, Matthias; Koeniger, Paul; Wanke, Heike; Hamutoko, Josefina; Himmelsbach, Thomas

    2016-02-01

    Stable isotopes (deuterium, 2H, and oxygen-18, 18O) of soil water were measured in the field using a liquid water isotope analyzer (tunable off-axis integrated cavity output spectroscope, OA-ICOS, LGR) and commercially available soil gas probes (BGL-30, UMS, Munich) in the semi-arid Cuvelai-Etosha Basin (CEB), Namibia. Results support the applicability of an in situ measurement system for the determination of stable isotopes in soil pore water. High spatial and temporal resolution was achieved in the study area with reasonable accuracy and measurements were in agreement with laboratory-based cryogenic vacuum extraction and subsequent cavity ring-down laser spectroscopic isotope analysis (CRDS, L2120-i, Picarro Inc.). After drift and span correction of the in situ isotope data, precision for over 140 measurements taken during two consecutive field campaigns (June and November 2014) was 1.8 and 0.48 ‰ for δ2H and δ18O, respectively. Mean measurement trueness is determined using quality check standards and was 5 and 0.3 ‰ for δ2H and δ18O, respectively. The isotope depth profiles are used quantitatively to calculate a soil water balance. The contribution of transpiration to total evapotranspiration ranged between 72 and 92 %. Shortly after a rain event, the contribution of transpiration was much lower, at 35 to 50 %. Potential limitations of such an in situ system are related to environmental conditions which could be minimized by using a temperature-controlled chamber for the laser spectrometer. Further, the applicability of the system using previously oven-dried soil material might be limited by physicochemical soil properties (i.e., clay minerals). Uncertainty in the in situ system is suggested to be reduced by improving the calibration procedure and further studying fractionation effects influencing the isotope ratios in the soil water, especially at low water contents. Furthermore, the influence of soil-respired CO2 on isotope values within the root zone

  12. GAS EMISSIONS IN PLANCK COLD DUST CLUMPS—A SURVEY OF THE J = 1-0 TRANSITIONS OF 12CO, 13CO, AND C18O

    A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC) in the J = 1-0 transitions of 12CO, 13CO, and C18O has been carried out using the Purple Mountain Observatory 13.7 m telescope. Six hundred seventy-three clumps were detected with 12CO and 13CO emission, and 68% of the sample has C18O emission. Additional velocity components were also identified. A close consistency of the three line peak velocities was revealed for the first time. Kinematic distances are given for all the velocity components, and half of the clumps are located within 0.5 and 1.5 kpc. Excitation temperatures range from 4 to 27 K, slightly larger than those of Td . Line width analysis shows that the majority of ECC clumps are low-mass clumps. Column densities NH2 span from 1020 to 4.5 × 1022 cm–2 with an average value of (4.4 ± 3.6) × 1021 cm–2. NH2 cumulative fraction distribution deviates from the lognormal distribution, which is attributed to optical depth. The average abundance ratio of the 13CO to C18O in these clumps is 7.0 ± 3.8, higher than the terrestrial value. Dust and gas are well coupled in 95% of the clumps. Blue profile asymmetry, red profile asymmetry, and total line asymmetry were found in less than 10% of the clumps, generally indicating that star formation is not yet developed. Ten clumps were mapped. Twelve velocity components and 22 cores were obtained. Their morphologies include extended diffuse, dense, isolated, cometary, and filament, of which the last is the majority. Twenty cores are starless, and only seven cores seem to be in a gravitationally bound state. Planck cold clumps are the most quiescent among the samples of weak red IRAS, infrared dark clouds, UC H II candidates, extended green objects, and methanol maser sources, suggesting that Planck cold clumps have expanded the horizon of cold astronomy.

  13. Determination of the δ2H and δ18O of soil water and water in plant matter; RSIL lab code 1700

    Revesz, Kinga M.; Buck, Bryan; Coplen, Tyler B.

    2012-01-01

    The purpose of the Reston Stable Isotope Laboratory lab code 1700 is to determine the δ2H/1H), abbreviated as δ2H, and the δ18O/16O), abbreviated as δ18O, of soil water and water in plant matter. This method is based on the observation that water and toluene form an azeotropic mixture at 84.1 °C. This temperature is substantially lower than the boiling points of water (100 °C) and toluene (110 °C), but water and toluene are immiscible at ambient temperature. The water content of a soil or plant is determined by weighing, drying, and reweighing a small amount of sample. Sufficient sample to collect 3 to 5 milliliters of water after distillation is loaded into a distillation flask. Sufficient toluene is added so that the sample is immersed throughout the entire distillation to minimize evaporation of water, which would affect the δ2H and δ18O values. The mixture of sample and toluene is heated in a flask to its boiling point (84.1 °C) so that water from the sample and toluene can distill together into a specially designed collection funnel. The temperature of 84.1 °C is maintained until the water has been quantitatively transferred to the collection funnel, at which time the temperature is raised to the boiling point of the remaining component (toluene, 110 °C). The collection funnel is maintained at ambient temperature so that the sample water and toluene can be separated physically. After separation, the sample water is purified by addition of paraffin wax to the container with the sample water, capping the container, and heating to approximately 60 °C to melt the wax. Trace amounts of toluene will dissolve in the wax, purifying the sample water for isotopic analysis. The isotopic composition of the purified water is then determined by equilibration with gaseous hydrogen or carbon dioxide, followed by dual-inlet isotope-ratio mass spectrometry. Because laser-absorption spectrometry is sensitive to organic compounds, such as trace toluene remaining in

  14. Assessing the relationship between the δ18O signatures of siliceous sponge spicules and water in a~tropical lacustrine environment (Minas Gerais, Brazil

    M. C. Matteuzzo

    2013-08-01

    Full Text Available Siliceous sponge spicules constitute an important siliceous component of lacustrine sediments, together with widespread diatom frustules. In contrast to diatom frustules, siliceous spicules are formed in sponges in an enzymatic way. Previous attempts to use their oxygen isotopic signature (δ18Osilica as a paleoenvironmental proxy have led to contradictory conclusions. These attempts demonstrated the need to further assess whether sponges form their silica in oxygen isotopic equilibrium with water. For this reason, we measured the δ18O signature of sponge spicules from a single freshwater species (Metania spinata grown on natural and artificial supports over nine months in a small Brazilian pond (Lagoa Verde, northwestern Minas Gerais. The δ18Osilica values were obtained using the infrared (IR laser-heating fluorination technique following a controlled isotopic exchange (CIE. The δ18O values (δ18Owater and temperature of the pond water were periodically measured and reconstructed over the course of the sponge growth. Assuming that silica may form continuously in the spicules, temperature and δ18Owater values over the months of growth were weighted using a sponge growth coefficient previously established for Metania spinata. The δ18Osilica values of sponges grown simultaneously and on similar substrates were scattered. No relationships were observed between the Δ18Osilica-water and water temperature when the reconstructed values were considered. Conversely, a positive correlation was obtained, with a coefficient of 0.3‰ °C–1 (R2 = 0.63, when δ18Owater values and water temperature at the time of sample collection were considered. Such a positive temperature coefficient clearly indicates that the freshwater sponge Metania spinata does not form its siliceous spicules in oxygen isotopic equilibrium with the pond water. Instead, one or several biologically controlled kinetic fractionation mechanisms may be in play during the various steps

  15. 2H NMR and 13C-IRMS analyses of acetic acid from vinegar, 18O-IRMS analysis of water in vinegar: international collaborative study report.

    Thomas, Freddy; Jamin, Eric

    2009-09-01

    An international collaborative study of isotopic methods applied to control the authenticity of vinegar was organized in order to support the recognition of these procedures as official methods. The determination of the 2H/1H ratio of the methyl site of acetic acid by SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and the determination of the 13C/12C ratio, by IRMS (isotope ratio mass spectrometry) provide complementary information to characterize the botanical origin of acetic acid and to detect adulterations of vinegar using synthetic acetic acid. Both methods use the same initial steps to recover pure acetic acid from vinegar. In the case of wine vinegar, the determination of the 18O/16O ratio of water by IRMS allows to differentiate wine vinegar from vinegars made from dried grapes. The same set of vinegar samples was used to validate these three determinations. The precision parameters of the method for measuring delta13C (carbon isotopic deviation) were found to be similar to the values previously obtained for similar methods applied to wine ethanol or sugars extracted from fruit juices: the average repeatability (r) was 0.45 per thousand, and the average reproducibility (R) was 0.91 per thousand. As expected from previous in-house study of the uncertainties, the precision parameters of the method for measuring the 2H/1H ratio of the methyl site were found to be slightly higher than the values previously obtained for similar methods applied to wine ethanol or fermentation ethanol in fruit juices: the average repeatability was 1.34 ppm, and the average reproducibility was 1.62 ppm. This precision is still significantly smaller than the differences between various acetic acid sources (delta13C and delta18O) and allows a satisfactory discrimination of vinegar types. The precision parameters of the method for measuring delta18O were found to be similar to the values previously obtained for other methods applied to wine and

  16. A Fiji multi-coral δ18O composite approach to obtaining a more accurate reconstruction of the last two-centuries of the ocean-climate variability in the South Pacific Convergence Zone region

    Dassié, Emilie P.; Linsley, Braddock K.; Corrège, Thierry; Wu, Henry C.; Lemley, Gavin M.; Howe, Steve; Cabioch, Guy

    2014-12-01

    The limited availability of oceanographic data in the tropical Pacific Ocean prior to the satellite era makes coral-based climate reconstructions a key tool for extending the instrumental record back in time, thereby providing a much needed test for climate models and projections. We have generated a unique regional network consisting of five Porites coral δ18O time series from different locations in the Fijian archipelago. Our results indicate that using a minimum of three Porites coral δ18O records from Fiji is statistically sufficient to obtain a reliable signal for climate reconstruction, and that application of an approach used in tree ring studies is a suitable tool to determine this number. The coral δ18O composite indicates that while sea surface temperature (SST) variability is the primary driver of seasonal δ18O variability in these Fiji corals, annual average coral δ18O is more closely correlated to sea surface salinity (SSS) as previously reported. Our results highlight the importance of water mass advection in controlling Fiji coral δ18O and salinity variability at interannual and decadal time scales despite being located in the heavy rainfall region of the South Pacific Convergence Zone (SPCZ). The Fiji δ18O composite presents a secular freshening and warming trend since the 1850s coupled with changes in both interannual (IA) and decadal/interdecadal (D/I) variance. The changes in IA and D/I variance suggest a re-organization of climatic variability in the SPCZ region beginning in the late 1800s to period of a more dominant interannual variability, which could correspond to a southeast expansion of the SPCZ.

  17. A study of some (sd)4 shell model states in 20F via the 18O(3He,p) reaction

    A microscopic two-particle DWBA analysis is carried out on the 18O(3He,p)20F reaction leading to the (sd)4 positive parity levels. The spectroscopic amplitudes were derived from the three single particle energies and sixty-three two-body matrix elements given by the shell model calculations or Halbert et al. based on an inert 16O core with the additional nucleons distributed in an unrestricted 1d5/2-2s1/2-1d3/2 model space. Angular distributions leading to several 1+, 2+, 3+, 4+ and 5+(sd)4 levels in 20F are fairly well reproduced. (author). 21 refs, 4 figs, 3 tabs

  18. 34S/32S and 18O/16O ratios of dissolved sulfate from interstitial water samples above gas hydrate bearing sediments of IODP Expedition 311, Cascadia

    Wortmann, U. G.; Chernyavsky, B. M.; Torres, M. E.; Kastner, M.

    2008-12-01

    Microbially mediated sulfate reduction affects the isotopic composition of dissolved and solid sulfur species in marine sediments. Although several details of the fractionation process remain controversial, the overall process is well understood and can be described as the sum of several mass dependent fractionations during the stepwise reduction of sulfate to sulfide. Experiments and field data show that the 18O/16O of sulfate is also modified in the presence of sulfate-reducing microorganisms. Here we use a reaction transport model to analyze these processes and to constrain the rates of organotrophic versus methanotrophic sulfate reduction. Our results show that even in cases where sulfate concentrations decline in a linear fashion, up to 50% of all sulfate is consumed by organotrophic sulfate reduction.

  19. Determination of energy expenditure during heavy exercise, normal daily activity, and sleep using the doubly-labelled-water (2H2 18O) method

    Energy expenditure of four subjects was measured by the doubly-labelled-water (2H2 18O) method to determine if energy expenditure could be determined over short periods. Three subjects were studied while they performed 8 h of heavy exercise in a laboratory environment. Urine and blood samples were taken before and after exercise. Estimated energy expended during 8 h of high-intensity exercise for three subjects was 757 +/- 118 kcal/h by the doubly-labelled-water method using urine and a two-point calculation, which compared favorably with 735 +/- 82 kcal/h obtained by respiratory gas exchange. For the fourth subject, daytime, nighttime, and daily energy expenditure was calculated by both the two-pair method and decay-curve analysis of urine and saliva samples collected in the morning and at night. Daytime and nighttime energy expenditures differed significantly (p less than 0.05)

  20. Geochemical tracers of new production: O2, N2, Ar and δ18O-O2 in surface waters of the subarctic Pacific Ocean

    The goal of this experiment was to test the utility of geochemical tracers for determining the rate of biological processes in surface waters in the Subarctic Pacific Ocean during the summers of 1987 and 1988. Measurements of O2/Ar, O2/N2 and 18O/16O-O2 by mass spectrometry along with oxygen and 222Rn-226Ra determinations were utilized in a mass balance model to derive rates of net oxygen production. Assuming that O2 production is balanced through a stoichiometric ratio be a net carbon export from the euphotic zone, the authors calculated a carbon export rate of 160 ± 40 mgC m-2d-1. This value is in accordance with sediment trap particulate carbon fluxes and mixed layer NO3 decrease measured in the SUPER program during the same period, implying that oxygen carbon and nitrogen mass balances agree, to within the error of the measurements, in this oceanic location

  1. Continental and local climatic influences on hydrology of eucalypt-Nothofagus ecosystems revealed by δ2H, δ13C, and δ18O of ecosystem samples

    Pfautsch, Sebastian; Gessler, Arthur; Rennenberg, Heinz; Weston, Christopher J.; Adams, Mark A.

    2010-03-01

    Marrying knowledge of variation in large-scale climatic parameters such as rainfall and evaporation to physiological ecology has long been argued as a powerful approach to advancing understanding of hydrology of catchments. Widely used hydrological models for assessing water yield depend on key plant attributes such as whether or not plant water use is coupled to atmospheric and/or soil water status. We analyzed δ2H and δ18O signatures of long-term rainwater collections from coastal sites near Melbourne, Australia, and in northwest Tasmania and compared them with their counterparts in rainwater, stream water, soil water, and twig water data collected over a 2 year period from south facing Eucalyptus-Nothofagus forests in the Cement Creek catchment of Mt. Donna Buang, about 70 km east of the city of Melbourne. Within the catchment, progressive evaporative enrichment among rain, soil, and twig water accounted for observed δ2H and δ18O signatures. We observed a major shift in both δ2H and δ18O signatures of rain and stream water between 2001/2002 and 2003. The shift was likely due to changes in atmospheric conditions and especially relative contributions to rainwater from oceanic and continental sources. Our plant isotope data argue strongly that radiation, not water, is a primary limitation for Nothofagus on Mt. Donna Buang. The δ18O and δ13C signatures of foliage varied with season and with topography. For the wettest and driest years in the 1978-2000 record, strong and consistent altitudinal gradients in δ13C of tree rings had a slope of between 4‰ and 5‰ km-1 of altitude. Our data highlight the importance of background (e.g., rainfall and atmospheric CO2) isotope data to interpretation of plant isotope data. Taken together with the literature, our isotope data lead us to conclude that (1) in periods of close to average rainfall, the observed meteoric water line at Mt. Donna Buang and at other stations in southeast Australia departs strongly in slope

  2. Possibilities and restrictions for recognizing of open and closed systems in Zechstein deposits with the aid of 2H and 18O

    An indirect method for determining of open and closed hydrological systems with the aid of 2H and 18O is described. According to the experience the method can be used in mining of copper bearing shale without any restrictions. If in salt mines saline or mirine relict waters are recognized, the hydrological system is a closed one. New methods are needed to distinguish between open systems with infiltrated solutions and closed systems with converted relict solutions if meteoric waters with high contents of MgCl2 were found, especially in the potash salt mining area on Werra river (GDR). So new indications must be found to recognize the converted solutions of closed systems. (author)

  3. Inhibition of α/β-K6P2W18O62· 10H2O on the Activity of Mushroom Tyrosinase and Its Antimicrobial Effects

    HU Xi-yu; CHEN Bing-nian; WANG Li; CHEN Fa-he

    2012-01-01

    Dawson-type phosphotungstic polyoxometalate a/β-K6P2W18O62·10H2O(P2W18) was synthesized and its inhibitory effect on the mushroom tyrosinase was investigated.It could inhibit diphenolase activity of mushroom tyrosinase as an irreversible inhibitor.When the concentration of the enzyme reached 0.0176 mg/mL,the concentration of P2W18 leading to 50% activity lost(IC50) was 0.05 mmol/L for monophenolase and 0.64 mmol/L for diphenolase.In addition,the antimicrobial activity of P2W18 was evaluated by zone of inhibition test.The results show that P2W18 possesses effective antimicrobial ability against Escherichia coli,Bacillus subtilis,yeast,especially Escherichia coli and yeast.

  4. Analysis of metal radioisotope impurities generated in [{sup 18}O]H{sub 2}O during the cyclotron production of fluorine-18

    Gillies, J.M. [Cancer Research-UK/UMIST Radiochemical Targeting and Imaging Group, Christie Hospital NHS Trust, Paterson Institute for Cancer Research, Wilmslow Road, Manchester, M20 4BX (United Kingdom)]. E-mail: jgillies@picr.man.ac.uk; Najim, N. [Cancer Research-UK/UMIST Radiochemical Targeting and Imaging Group, Christie Hospital NHS Trust, Paterson Institute for Cancer Research, Wilmslow Road, Manchester, M20 4BX (United Kingdom); School of Chemical Engineering and Analytical Sciences, University of Manchester, P.O. Box 88, Manchester, M60 1QD (United Kingdom); Zweit, J. [Cancer Research-UK/UMIST Radiochemical Targeting and Imaging Group, Christie Hospital NHS Trust, Paterson Institute for Cancer Research, Wilmslow Road, Manchester, M20 4BX (United Kingdom); School of Chemical Engineering and Analytical Sciences, University of Manchester, P.O. Box 88, Manchester, M60 1QD (United Kingdom)

    2006-04-15

    We show the separation of metal radioistope impurities using capillary electrophoresis (CE). The methodology used is an improvement of existent protocols for separation of stable metal ions. Production of fluorine-18 using [{sup 18}O]H{sub 2}O-enriched water encased in a titanium target body results in the production of several metal radioisotope impurities. Optimisation of the conditions for CE separation of the metal radioisotope impurities incorporated the use of 6 mM 18-Crown-6 in combination with 12 mM glycolic acid as complexing agents within the running buffer (10 mM pyridine, pH 4.0). Using this optimised procedure, we were able to separate and detect a number of metal radioisotopes, including chromium, cobalt, manganese, vanadium and berillium, within the fM concentration range.

  5. Study on particle emission in the light-heavy ion fussion reactions: 14N, sup(16,18) O + 12C

    From the energy spectra of light particles produced in light heavy ion induced reactions, level densities of the final nuclei as well as the critical angular momenta for fussion may be obtained. The 14N, sup(16,18) O + 12C reactions were investigated in the energy range 30 MeV < E sub(LAB) < 60 MeV. Detailed angular distributions of the light particles (p, d, t, α) emitted in the process were obtained. Fits of the magnitude and shape of the spectra, by means of statistical model calculations were used to extract final nuclei level densities. The shape of the spectra and the ratio σ(α) σ(p) are shown to be sensitive to the fussion critical angular momentum (J sub(cr)), offering an alternative method for the total fussion cross-section determination. (Author)

  6. Determination of energy expenditure during heavy exercise, normal daily activity, and sleep using the doubly-labelled-water (/sup 2/H/sub 2/ 18O) method

    Stein, T.P.; Hoyt, R.W.; Settle, R.G.; O' Toole, M.; Hiller, W.D.

    1987-03-01

    Energy expenditure of four subjects was measured by the doubly-labelled-water (/sup 2/H/sub 2/ 18O) method to determine if energy expenditure could be determined over short periods. Three subjects were studied while they performed 8 h of heavy exercise in a laboratory environment. Urine and blood samples were taken before and after exercise. Estimated energy expended during 8 h of high-intensity exercise for three subjects was 757 +/- 118 kcal/h by the doubly-labelled-water method using urine and a two-point calculation, which compared favorably with 735 +/- 82 kcal/h obtained by respiratory gas exchange. For the fourth subject, daytime, nighttime, and daily energy expenditure was calculated by both the two-pair method and decay-curve analysis of urine and saliva samples collected in the morning and at night. Daytime and nighttime energy expenditures differed significantly (p less than 0.05).

  7. Carbon cycling in primary production bottle incubations: inferences from grazing experiments and photosynthetic studies using 14C and 18O in the Arabian Sea

    Laws, Edward A.; Landry, Michael R.; Barber, Richard T.; Campbell, Lisa; Dickson, Mary-Lynn; Marra, John

    Estimates of photosynthesis based on the incorporation of 14C-labeled inorganic carbon into particulate carbon were compared to estimates of gross photosynthesis based on net O 2 production and the production of 18O2 from H218O during the US Joint Global Ocean Flux Study (US JGOFS) Arabian Sea process cruises. For samples incubated below the surface and at optical depthsphotorespiration, dark respiration, excretion, and grazing effects on the two estimates of photosynthesis. The 14C uptake : gross photosynthesis ratio was distinctly higher (0.62) for samples incubated at the surface. This result is likely due to UV light effects, since the O 2 and 14C incubations were done in quartz and polysulfone bottles, respectively. The 14C uptake : gross photosynthesis ratio was lower (0.31) for bottles incubated at optical depths>3. This result probably reflects an increase in the ratio of dark respiration to net photosynthesis in the vicinity of the compensation light level.

  8. Search for quasifission in 12C + 238U and 18O + 232Th reactions at near and sub-barrier energies

    The main motivation of this present work is to study the onset of quasifission process in the fissility region > 0.8. It was observed that angular distribution of fission fragments produced in reaction in this fissility region showed anomalously large anisotropies at subbarrier energies as compared to SSPM, implying presence of pre-equilibrium fission. Here, mass-angle correlation studies of 12C + 238U and 18O + 232Th reactions has been reported, forming same compound nucleus 250Cf (Fissility = 0.86), at similar excitation energy and angular momentum. The measurements were carried out in the energy range Ecm /Vb ∼ 0.88 - 1.1, where Ecm is the energy in centre of mass frame and Vb is the Coulomb barrier

  9. Decadal time scale variability recorded in the Quelccaya summit ice core {delta}{sup 18}O isotopic ratio series and its relation with the sea surface temperature

    Melice, J.L. [Louvain Univ., Louvain-la-Neuve (Belgium). Inst. d`Astronomie et de Geophysique; Roucou, P. [Centre de Recherches de Climatologie, Universite de Bourgogne, Faculte des Sciences Gabriel, B.P. 138, F-21000 Dijon (France)

    1998-02-01

    The spectral characteristics of the {delta}{sup 18}O isotopic ratio time series of the Quelccaya ice cap summit core are investigated with the multi taper method (MTM), the singular spectrum analysis (SSA) and the wavelet transform (WT) techniques for the 500 y long 1485-1984 period. The most significant (at the 99.8% level) cycle according to the MTM F-test has a period centered at 14.4 y while the largest variance explaining oscillation according to the SSA technique has a period centered at 12.9 y. The stability over time of these periods is investigated by performing evolutive MTM and SSA on the 500 y long {delta}{sup 18}O series with a 100 y wide moving window. It is shown that the cycles with largest amplitude and that the oscillations with largest extracting variance have corresponding periods aggregated around 13.5 y that are very stable over the period between 1485 and 1984. The WT of the same isotopic time series reveals the existence of a main oscillation around 12 y which are also very stable in time. The relation between the isotopic data at Quelccaya and the annual sea surface temperature (SST) field anomalies is then evaluated for the overlapping 1919-1984 period. Significant global correlation and significant coherency at 12.1 y are found between the isotopic series and the annual global sea surface temperature (GSST) series. Moreover, the correlation between the low (over 8 y) frequency component of the isotopic time series and the annual SST field point out significant values in the tropical North Atlantic. This region is characterized by a main SST variability at 12.8 y. (orig.) With 13 figs., 2 tabs., 52 refs.

  10. Natural chlorate in the environment: Application of a new IC-ESI/MS/MS method with a Cl18O3- internal standard

    Rao, Balaji; Hatzinger, Paul B.; Böhlke, John Karl; Sturchio, Neil C.; Andraski, Brian J.; Eckardt, Frank D.; Jackson, W. Andrew

    2010-01-01

    A new ion chromatography electrospray tandem mass spectrometry (IC-ESI/MS/MS) method has been developed for quantification and confirmation of chlorate (ClO3-) in environmental samples. The method involves the electro-chemical generation of isotopically labeled chlorate internal standard (Cl18O3-) using 18O water (H218O). The standard was added to all samples prior to analysis thereby minimizing the matrix effects that are associated with common ions without the need for expensive sample pretreatments. The method detection limit (MDL) for ClO3- was 2 ng L-1 for a 1 mL volume sample injection. The proposed method was successfully applied to analyze ClO3- in difficult environmental samples including soil and plant leachates. The IC-ESI/MS/MS method described here was also compared to established EPA method 317.0 for ClO3- analysis. Samples collected from a variety of environments previously shown to contain natural perchlorate (ClO 4-) occurrence were analyzed using the proposed method and ClO3- was found to co-occur with ClO4- at concentrations ranging from 500 mg kg-1 in caliche salt deposits from the Atacama Desert in Chile. Relatively low concentrations of ClO3- in some natural groundwater samples (-1) analyzed in this work may indicate lower stability when compared to ClO4- in the subsurface. The high concentrations of ClO3- in caliches and soils (3-6 orders of magnitude greater) as compared to precipitation samples indicate that ClO3-, like ClO4-, may be atmospherically produced and deposited, then concentrated in dry soils, and is possibly a minor component in the biogeochemical cycle of chlorine.

  11. Reconstruction of drip-water δ18O based on calcite oxygen and clumped isotopes of speleothems from Bunker Cave (Germany

    T. Kluge

    2013-02-01

    Full Text Available The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilibrium effects. The extent of kinetic fractionation co-varies in Δ47 and δ18O so that it can be used to account for disequilibrium in δ18O and to extract the past drip-water composition. Here we apply this approach to stalagmites from Bunker Cave (Germany and calculate drip-water δ18Ow values for the Eemian, MIS3, and the Holocene, relying on independent temperature estimates and accounting for disequilibrium. Applying the co-variation method to modern calcite precipitates yields drip-water δ18Ow values in agreement with modern cave drip-water δ18Ow of −7.9 ± 0.3‰, despite large and variable disequilibrium effects in both calcite δ18Oc and Δ47. Reconstructed paleo-drip-water δ18Ow values are lower during colder periods (e.g., MIS3: −8.6 ± 0.4‰ and the early Holocene at 11 ka: −9.7 ± 0.2‰ and show higher values during warmer climatic periods (e.g., the Eemian: −7.6 ± 0.2‰ and the Holocene Climatic Optimum: −7.2 ± 0.3‰. This new approach offers a unique possibility for quantitative climate reconstruction including the assessment of past hydrological conditions while accounting for disequilibrium effects.

  12. Reconstruction of drip-water δ18O based on calcite oxygen and clumped isotopes of speleothems from Bunker Cave (Germany

    A. Wackerbarth

    2012-07-01

    Full Text Available The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilibrium effects. The extent of kinetic fractionation co-varies in Δ47 and δ18O so that it can be used to account for disequilibrium in δ18O and to extract the past drip-water composition. Here we apply this approach to stalagmites from Bunker Cave (Germany and calculate drip-water δ18Ow values for the Eemian, Marine Isotope Stage (MIS 3, and the Holocene, relying on independent temperature estimates and accounting for disequilibrium. Applying the co-variation method to modern calcite precipitates yields drip-water δ18Ow values in agreement with modern cave drip-water δ18Ow of −7.9 ± 0.3‰, despite large and variable disequilibrium effects in both calcite δ18Oc and Δ47. Reconstructed paleo-drip-water δ18Ow values are lower during colder periods (e.g., MIS 3: −8.5 ± 0.4‰ and the early Holocene at 11 kyr: −9.3 ± 0.1‰ and show higher values during warmer climatic periods (e.g., the Eemian: −7.5 ± 0.2‰ and the Holocene Climatic Optimum: −7.2 ± 0.3‰. This new approach offers a unique possibility for quantitative climate reconstruction including the assessment of past hydrological conditions while accounting for disequilibrium effects.

  13. CO/sub 2/ production in animals: analysis of potential errors in the doubly labeled water method. [/sup 3/H and /sup 18/O

    Nagy, K.A.

    1979-03-01

    Laboratory validation studies indicate that doubly labeled water (/sup 3/HH/sup 18/O and /sup 2/HH/sup 18/O) measurements of CO/sub 2/ production are accurate to within +-9% in nine species of mammals and reptiles, a bird, and an insect. However, in field studies, errors can be much larger under certain circumstances. Isotopic fraction of labeled water can cause large errors in animals whose evaporative water loss comprises a major proportion of total water efflux. Input of CO/sub 2/ across lungs and skin caused errors exceeding +80% in kangaroo rats exposed to air containing 3.4% unlabeled CO/sub 2/. Analytical errors of +-1% in isotope concentrations can cause calculated rates of CO/sub 2/ production to contain errors exceeding +-70% in some circumstances. These occur: 1) when little decline in isotope concentractions has occured during the measurement period; 2) when final isotope concentrations closely approach background levels; and 3) when the rate of water flux in an animal is high relative to its rate of CO/sub 2/ production. The following sources of error are probably negligible in most situations: 1) use of an inappropriate equation for calculating CO/sub 2/ production, 2) variations in rates of water or CO/sub 2/ flux through time, 3) use of H/sub 2/O-18 dilution space as a measure of body water volume, 4) exchange of 0-18 between water and nonaqueous compounds in animals (including excrement), 5) incomplete mixing of isotopes in the animal, and 6) input of unlabeled water via lungs and skin. Errors in field measurements of CO/sub 2/ production can be reduced to acceptable levels (< 10%) by appropriate selection of study subjects and recapture intervals.

  14. Cobalt Polyoxometalate Co4V2W18O68(10-): A Critical Investigation of Its Synthesis, Purity, and Observed (51)V Quadrupolar NMR.

    Folkman, Scott J; Kirner, Joel T; Finke, Richard G

    2016-06-01

    The vanadium-containing cobalt polyoxometalate (Co-POM) Co4V2W18O68(10-) (hereafter Co4V2W18) has been reported to be a stable, homogeneous water-oxidation catalyst, one with a claimed record turnover frequency that is also reportedly 200-fold faster than its phosphorus congener, Co4P2W18O68(10-). The claimed superior water-oxidation catalysis activity of the vanadium congener, Co4V2W18, rests squarely on the reported synthesis of Co4V2W18, its purity, and its stability in both the solid-state and in solution. Attempts to repeat the preparation of Co4V2W18 by either of two literature syntheses, along with the other studies reported herein, led to the discovery of multiple, convoluted problems in the prior literature of Co4V2W18. The three most serious of those problems proved to be the prior misunderstanding of the quadrupolar (herein (51)V) NMR peak widths in complexes that also contain paramagnetic metals such as Co(II), the incorrect assignment of a -506.8 ppm (51)V NMR to Co4V2W18, and then the use of that -506.8 peak to argue for the stability of Co4V2W18 in solution. The results are reported in a somewhat historical, "story" fashion en route to elucidating and fully supporting the 11 insights and take-home messages listed in the Summary and Conclusions section. PMID:27159211

  15. Microwave-enhanced electrochemical cycling performance of the LiNi0.2Mn1.8O4 spinel cathode material at elevated temperature.

    Raju, Kumar; Nkosi, Funeka P; Viswanathan, Elumalai; Mathe, Mkhulu K; Damodaran, Krishnan; Ozoemena, Kenneth I

    2016-05-14

    The well-established poor electrochemical cycling performance of the LiMn2O4 (LMO) spinel cathode material for lithium-ion batteries at elevated temperature stems from the instability of the Mn(3+) concentration. In this work, a microwave-assisted solid-state reaction has been used to dope LMO with a very low amount of nickel (i.e., LiNi0.2Mn1.8O4, herein abbreviated as LMNO) for lithium-ion batteries from Mn3O4 which is prepared from electrolytic manganese oxide (EMD, γ-MnO2). To establish the impact of microwave irradiation on the electrochemical cycling performance at an elevated temperature (60 °C), the Mn(3+) concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, (6)LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). The microwave-treated sample (LMNOmic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn(3+) content, promoting structural and cycle stability at elevated temperature. At room temperature, both the pristine (LMNO) and microwave-treated (LMNOmic) samples gave comparable cycling performance (>96% capacity retention and ca. 100% coulombic efficiency after 100 consecutive cycling). However, at an elevated temperature (60 °C), the LMNOmic gave an improved cycling stability (>80% capacity retention and ca. 90% coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi0.2Mn1.8O4 at elevated temperature and lithium-ion diffusion kinetics has been clearly demonstrated. PMID:27113855

  16. Herschel/HIFI Search for H_2^{17}O and H_2^{18}O in IRC+10216: Constraints on Models for the Origin of Water Vapor

    Neufeld, David A.; Tolls, Volker; Agúndez, Marcelino; González-Alfonso, Eduardo; Decin, Leen; Daniel, Fabien; Cernicharo, José; Melnick, Gary J.; Schmidt, Miroslaw; Szczerba, Ryszard

    2013-04-01

    We report the results of a sensitive search for the minor isotopologues of water, H_2^{17}O and H_2^{18}O, toward the carbon-rich asymptotic giant branch star IRC+10216 (a.k.a. CW Leonis) using the HIFI instrument on the Herschel Space Observatory. This search was motivated by the fact that any detection of isotopic enhancement in the H_2^{17}O and H_2^{18}O abundances would have strongly implicated CO photodissociation as the source of the atomic oxygen needed to produce water in a carbon-rich circumstellar envelope. Our observations place an upper limit of 1/470 on the H_2^{17}O/H_2^{16}O abundance ratio. Given the isotopic 17O/16O ratio of 1/840 inferred previously for the photosphere of IRC+10216, this result places an upper limit of a factor 1.8 on the extent of any isotope-selective enhancement of H_2^{17}O in the circumstellar material, and provides an important constraint on any model that invokes CO photodissociation as the source of O for H2O production. In the context of the clumpy photodissociation model proposed previously for the origin of water in IRC+10216, our limit implies that 12C16O (not 13C16O or SiO) must be the dominant source of 16O for H2O production, and that the effects of self-shielding can only have reduced the 12C16O photodissociation rate by at most a factor ~2. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  17. Coordinated Isotopic and Mineral Characterization of Highly Fractionated 18O-Rich Silicates in the Queen Alexandra Range 99177 CR3 Chondrite

    Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

    2016-01-01

    Carbonaceous chondrites contain a mixture of solar system condensates, pre-solar grains, and primitive organic matter. Each of these materials record conditions and processes in different regions of the solar nebula, on the meteorite parent body, and beyond the solar system. Oxygen isotopic studies of meteorite components can trace interactions of distinct oxygen isotopic reservoirs in the early solar system and secondary alteration processes. The O isotopic compositions of the earliest solar system condensates fall along a carbonaceous chondrite anhydrous mineral (CCAM) line of slope approximately 1 in a plot of delta 17O against delta 18O. This trend is attributed to mixing of material from 16O-poor and 16O-rich reservoirs. Secondary processing can induce mass-dependent fractionation of the O isotopes, shifting these compositions along a line of slope approximately 0.52. Substantial mass-dependent fractionation of O isotopes has been observed in secondary minerals in CAIs, calcite, and FUN inclusions. These fractionations were caused by significant thermal or aqueous alteration. We recently reported the identification of four silicate grains with extremely fractionated O isotopic ratios (delta 18O equals 37 - 55 per mille) in the minimally altered CR3 chondrite QUE 99177. TEM analysis of one grain indicates it is a nebular condensate that did not experience substantial alteration. The history of these grains is thus distinct from those of the aforementioned fractionated materials. To constrain the origin of the silicate grains, we conducted further Mg and Fe isotopic studies and TEM analyses of two grains.

  18. Quantification of Competing H3PO4 Versus HPO3 + H2O Neutral Losses from Regioselective 18O-Labeled Phosphopeptides

    Cui, Li; Yapici, Ipek; Borhan, Babak; Reid, Gavin E.

    2014-01-01

    Abundant neutral losses of 98 Da are often observed upon ion trap CID-MS/MS of protonated phosphopeptide ions. Two competing fragmentation pathways are involved in this process, namely, the direct loss of H3PO4 from the phosphorylated residue and the combined losses of HPO3 and H2O from the phosphorylation site and from an additional site within the peptide, respectively. These competing pathways produce product ions with different structures but the same m/z values, potentially limiting the utility of CID-MS3 for phosphorylation site localization. To quantify the relative contributions of these pathways and to determine the conditions under which each pathway predominates, we have examined the ion trap CID-MS/MS fragmentation of a series of regioselective 18O-phosphate ester labeled phosphopeptides prepared using novel solution-phase amino acid synthesis and solid-phase peptide synthesis methodologies. By comparing the intensity of the -100 Da (-H3PO3 18O) versus -98 Da (-[HPO3 + H2O]) neutral loss product ions formed upon MS/MS, quantification of the two pathways was achieved. Factors that affect the extent of formation of the competing neutral losses were investigated, with the combined loss pathway predominantly occurring under conditions of limited proton mobility, and with increased combined losses observed for phosphothreonine compared with phosphoserine-containing peptides. The combined loss pathway was found to be less dominant under ion activation conditions associated with HCD-MS/MS. Finally, the contribution of carboxylic acid functional groups and backbone amide bonds to the water loss in the combined loss fragmentation pathway was determined via methyl esterification and by examination of a phosphopeptide lacking side-chain hydroxyl groups.

  19. Reconstructing climate processes driving variability in precipitation sources from mid to late Holocene speleothem δ18O records from the Southwest US

    Wong, C. I.; Nusbaumer, J. M.; Banner, J.

    2015-12-01

    Independent co-variation of speleothem δ18O values and other moisture-sensitive speleothem proxies (e.g., growth rate, trace element concentrations) in recently published Holocene stalagmite records from Texas and New Mexico suggest a decoupling between precipitation amounts and precipitation sources over the southwest US. There is, however, limited understanding of the relation between precipitation sources and precipitation amounts and the climate processes governing variability in the region's precipitation sources. To address this, we use source water tags to track precipitation derived from Pacific and Atlantic Oceans during a simulation of modern (1975-2013) climate. We find distinct patterns in the spatial distribution of the fraction of Pacific-derived winter precipitation are associated with unique atmospheric states. High pressure ridging reflected by 500 hPa geopotential heights result in weaker zonal winds and stronger northerly winds over the western US. Under these conditions, Pacific-derived moisture propagates further to the east, and Atlantic-derived moisture is suppressed over southern US. Conversely, 500 hPa geopotential heights that are latitudinally streamline result in strong zonal winds across the entire US. Under these conditions, the fraction of West Pacific-derived precipitation is limited to higher latitudes, and the fraction of far East Pacific- and Atlantic-derived precipitation is enhanced across the Southwest and Southern US, respectively. Further analysis of this data set will assess the teleconnections that link the distinct atmospheric conditions over the US with the state of the ocean and atmosphere over the Pacific and Atlantic Oceans. The results will be applied to reconstructing variability in the climate dynamics governing moisture transport to the southwest US during the mid to late Holocene as reflected by speleothem δ18O records in the region.

  20. A Survey of \\delta18O and \\delta15N Ratios in Ground Water from an Agricultural Community in the San Joaquin Valley, California

    Glowacki, S. D.; Suen, C. J.

    2004-12-01

    We studied ground water samples from domestic and monitoring wells in an agricultural community in the eastern side of the San Joaquin Valley, California. The study area is rich in alluvial soils creating an extremely fertile farmland. Livestock farms and agricultural fields are abundant in the area. Fifty-four ground water samples were analyzed for \\delta18O and \\delta15N in dissolved nitrate, in addition to nutrients and major minerals. Nitrate concentration levels in groundwater are elevated and affected by agricultural and other activities. Possible sources of nutrients include: a municipal waste-water treatment facility, a raisin processing plant, a meat processing plant, a turkey farm, diary operations, and agricultural fields. However, except for the turkey f