Relevant bibliographies by topics / 18-O isotope exchange

Academic literature on the topic '18-O isotope exchange'

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Published: 4 June 2021
Last updated: 28 January 2023

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Journal articles on the topic "18-O isotope exchange"

1

Fedorova, O. M., Anatoly Yakovlevich Fishman, Tatiana Eugenievna Kurennykh, Vladimir Borisovich Vykhodets, and V. B. Vykhodets. "Isotope Exchange between 18O2 Gas and Mechanoactivated Oxide NdMnO3+δ." Defect and Diffusion Forum 333 (January 2013): 193–98. http://dx.doi.org/10.4028/www.scientific.net/ddf.333.193.

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sotope exchange of oxygen 18О2 with oxides NdMnO3+δ was investigated. The oxide was obtained from oxides Nd2O3 and Mn2O3 using a ceramic technology with annealing in air at 1400°C for 90 hours followed by cooling in a furnace. A planetary mill AGO-2 with a centrifugal factor of g = 60 was used for mechanical treatment of oxides. The study of isotope exchange was carried out by nuclear microanalysis. The concentration of the isotopes 18O and 16O in oxides was determined using a Van de Graaff accelerator and 18O(p, α)15N and 16O(d, p)17O* reactions at the energies of incident beams 762 and 900 keV. Isothermal annealing of powders was carried out in oxygen, enriched to 80% by the isotope 18O. It was established that the concentration of the isotope 18O in mechanically activated powders was several times higher than in the initial micropowder under the same conditions of annealing. The effect increased with increasing of mechanical activation time (30 - 300 s). The isotope exchange parameters connected with the processes at the boundaries of the particles of mechano-activated powder and within their volume were analyzed.
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Szanyi, J., and J. H. Kwak. "15N2 formation and fast oxygen isotope exchange during pulsed 15N18O exposure of MnOx/CeO2." Chem. Commun. 50, no. 95 (2014): 14998–5001. http://dx.doi.org/10.1039/c4cc05427j.

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3

Gizhevskii, Boris A., Anatoly Yakovlevich Fishman, E. A. Kozlov, Tatiana Eugenievna Kurennykh, S. A. Petrova, I. Sh Trakhtenberg, Vladimir Borisovich Vykhodets, V. B. Vykhodets, and Robert Grigorievich Zakharov. "Oxygen Isotope Exchange between Gaseous Phase Enriched with 18O Isotope and Nanocrystal Oxides LaMnO3+δ Obtained by Severe Plastic Deformation." Defect and Diffusion Forum 273-276 (February 2008): 233–38. http://dx.doi.org/10.4028/www.scientific.net/ddf.273-276.233.

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The kinetics of the isotope exchange between gaseous oxygen enriched with the 18O isotope and two LaMnO3+δ oxide samples – a nanopowder and a bulk nanocrystal – has been studied. The 18O isotope concentration has been measured by the acceleration nuclear microanalysis method. The coefficients of the volume and the nanograin boundary self-diffusion of oxygen have been evaluated at 500 °C. They are equal to 3.5·10 −20 and 1.5·10 −13 cm2/s, respectively.
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Fishman, Anatoly Yakovlevich, G. A. Kozhina, Tatiana Eugenievna Kurennykh, E. V. Vykhodets, and Vladimir Borisovich Vykhodets. "Isotope Exchange between 18O2 Gas and Mechanoactivated Oxides of the Family Rare Earth – Manganese – Oxygen." Defect and Diffusion Forum 354 (June 2014): 153–58. http://dx.doi.org/10.4028/www.scientific.net/ddf.354.153.

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The results of measurements of the bulk diffusion of tracer oxygen atoms in the oxides LnMnO3+δ (Ln = La, Nd, Sm) in the temperature range 400 – 750°С are presented. The measurements were carried out on micro-and nanopowders. Nanoscale powders were prepared by mechanical activation. A method based on the study of the kinetics of oxygen isotope exchange between the powder and gaseous oxygen enriched with 18O isotope was used to obtain data on the diffusion coefficients. The average concentration of 18O isotope in the powders was measured using NRA technique. The obtained diffusion coefficients lay in the range of 10-21 - 10-24 m2/s, the diffusion activation energy for all the oxides have been close to 1 eV. These results suggest that the migration of tracer oxygen in oxides LаMnO3+δ, NdMnO3+δ and SmMnO3+δ at low temperatures is realized via structural defects. As for the oxide LaMnO3+δ, its oxygen diffusion coefficients at low temperatures have been lower than the values extrapolated from high temperatures. Such behavior of diffusion properties has not been previously observed in other metal oxides. In this regard, the vacancy formation energy in the rare earth manganites has been supposed to increase with decreasing temperature.
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Schoeller, D. A., E. Ravussin, Y. Schutz, K. J. Acheson, P. Baertschi, and E. Jequier. "Energy expenditure by doubly labeled water: validation in humans and proposed calculation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 250, no. 5 (May 1, 1986): R823—R830. http://dx.doi.org/10.1152/ajpregu.1986.250.5.r823.

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To further validate the doubly labeled water method for measurement of CO2 production and energy expenditure in humans, we compared it with near-continuous respiratory gas exchange in nine healthy young adult males. Subjects were housed in a respiratory chamber for 4 days. Each received 2H2(18)O at either a low (n = 6) or a moderate (n = 3) isotope dose. Low and moderate doses produced initial 2H enrichments of 5 and 10 X 10(-3) atom percent excess, respectively, and initial 18O enrichments of 2 and 2.5 X 10(-2) atom percent excess, respectively. Total body water was calculated from isotope dilution in saliva collected at 4 and 5 h after the dose. CO2 production was calculated by the two-point method using the isotopic enrichments of urines collected just before each subject entered and left the chamber. Isotope enrichments relative to predose samples were measured by isotope ratio mass spectrometry. At low isotope dose, doubly labeled water overestimated average daily energy expenditure by 8 +/- 9% (SD) (range -7 to 22%). At moderate dose the difference was reduced to +4 +/- 5% (range 0-9%). The isotope elimination curves for 2H and 18O from serial urines collected from one of the subjects showed expected diurnal variations but were otherwise quite smooth. The overestimate may be due to approximations in the corrections for isotope fractionation and isotope dilution. An alternative approach to the corrections is presented that reduces the overestimate to 1%.
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Akers, Pete D., Ben G. Kopec, Kyle S. Mattingly, Eric S. Klein, Douglas Causey, and Jeffrey M. Welker. "Baffin Bay sea ice extent and synoptic moisture transport drive water vapor isotope (<i>δ</i><sup>18</sup>O, <i>δ</i><sup>2</sup>H, and deuterium excess) variability in coastal northwest Greenland." Atmospheric Chemistry and Physics 20, no. 22 (November 19, 2020): 13929–55. http://dx.doi.org/10.5194/acp-20-13929-2020.

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Abstract. At Thule Air Base on the coast of Baffin Bay (76.51∘ N, 68.74∘ W), we continuously measured water vapor isotopes (δ18O, δ2H) at a high frequency (1 s−1) from August 2017 through August 2019. Our resulting record, including derived deuterium excess (dxs) values, allows an analysis of isotopic–meteorological relationships at an unprecedented level of detail and duration for high Arctic Greenland. We examine isotopic variability across multiple temporal scales from daily to interannual, revealing that isotopic values at Thule are predominantly controlled by the sea ice extent in northern Baffin Bay and the synoptic flow pattern. This relationship can be identified through its expression in the following five interacting factors: (a) local air temperature, (b) local marine moisture availability, (c) the North Atlantic Oscillation (NAO), (d) surface wind regime, and (e) land-based evaporation and sublimation. Each factor's relative importance changes based on the temporal scale and in response to seasonal shifts in Thule's environment. Winter sea ice coverage forces distant sourcing of vapor that is isotopically light from fractionation during transport, while preventing isotopic exchange with local waters. Sea ice breakup in late spring triggers a rapid isotopic change at Thule as the newly open ocean supplies warmth and moisture that has ∼10 ‰ and ∼70 ‰ higher δ18O and δ2H values, respectively, and ∼10 ‰ lower dxs values. Sea ice retreat also leads to other environmental changes, such as sea breeze development, that radically alter the nature of relationships between isotopes and many meteorological variables in summer. On synoptic timescales, enhanced southerly flow promoted by negative NAO conditions produces higher δ18O and δ2H values and lower dxs values. Diel isotopic cycles are generally very small as a result of a moderated coastal climate and the counteracting isotopic effects of the sea breeze, local evaporation, and convection. Future losses in Baffin Bay's sea ice extent will likely shift mean annual isotopic compositions toward more summer-like values, and local glacial ice could potentially preserve isotopic evidence of past reductions. These findings highlight the influence that the local environment can have on isotope dynamics and the need for dedicated, multiseason monitoring to fully understand the controls on water vapor isotope variability.
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Alasino, P., C. Casquet, C. Galindo, R. Pankhurst, C. Rapela, J. Dahlquist, C. Recio, E. Baldo, M. Larrovere, and C. Ramacciotti. "O–H–Sr–Nd isotope constraints on the origin of the Famatinian magmatic arc, NW Argentina." Geological Magazine 157, no. 12 (May 4, 2020): 2067–80. http://dx.doi.org/10.1017/s0016756820000321.

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AbstractWe report a study of whole-rock O–H–Sr–Nd isotopes of Ordovician igneous and metamorphic rocks exposed at different crustal palaeodepths along c. 750 km in the Sierras Pampeanas, NW Argentina. The isotope compositions preserved in the intermediate rocks (mostly tonalite) (average δ18O = +8.7 ± 0.5‰, δD = −73 ± 14‰, 87Sr/86Srt = 0.7088 ± 0.0001 and εNdt = −4.5 ± 0.6) show no major difference from those of most of the mafic rocks (average δ18O = +8 ± 0.8‰, δD = −84 ± 18‰, 87Sr/86Srt = 0.7082 ± 0.0016 and εNdt = −4 ± 1.1), suggesting that most of their magmas acquired their crustal characteristics in the mantle. The estimate of assimilation of crustal material (δ18O = +12.2 ± 1.7‰, δD = −89 ± 21‰, 87Sr/86Srt = 0.7146 ± 0.0034 and εNdt = −6.9 ± 0.7) by the tonalite is in most samples within the range 10–20%. Felsic magmas that reached upper crustal levels had isotope values (δ18O = +9.9 ± 1.5‰, δD= −76 ± 5‰, 87Sr/86Srt = 0.7067 ± 0.0010, εNdt = −3.5 ± 1.4) suggesting that they were not derived by fractionation of the contaminated intermediate magmas, but evolved from different magma batches. Some rocks of the arc, both igneous (mostly gabbro and tonalite) and metamorphic, underwent restricted interaction with meteoric fluids. Reported values of δ18O of magmatic zircons from the Famatinian arc rocks (+6 to +9‰) are comparable to our δ18O whole-rock data, indicating that pervasive oxygen isotope exchange in the lower crust was not a major process after zircon crystallization.
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Studer, M. S., R. T. W. Siegwolf, M. Leuenberger, and S. Abiven. "Multi-isotope labelling (<sup>13</sup>C, <sup>18</sup>O, <sup>2</sup>H) of fresh assimilates to trace organic matter dynamics in the plant-soil system." Biogeosciences Discussions 11, no. 11 (November 18, 2014): 15911–43. http://dx.doi.org/10.5194/bgd-11-15911-2014.

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Abstract. Isotope labelling is a powerful tool to study elemental cycling within terrestrial ecosystems. Here we describe a new multi-isotope technique to label organic matter (OM). We exposed poplars (Populus deltoides x nigra) for 14 days to an atmosphere enriched in 13CO2 and depleted in 2H218O. After one week, the water-soluble leaf OM (δ13C = 1346 ± 162‰) and the leaf water were strongly labelled (δ18O = −63± 8‰, δ2H = −156 ± 15‰). The leaf water isotopic composition was between the atmospheric and stem water, indicating a considerable diffusion of vapour into the leaves (58–69%). The atomic ratios of the labels recovered (18O/13C, 2H/13C) were 2–4 times higher in leaves than in the stems and roots. This either indicates the synthesis of more condensed compounds (lignin vs. cellulose) in roots and stems, or be the result of O and H exchange and fractionation processes during transport and biosynthesis. We demonstrate that the three major OM elements (C, O, H) can be labelled and traced simultaneously within the plant. This approach could be of interdisciplinary interest for the fields of plant physiology, paleoclimatic reconstruction or soil science.
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Téllez, Helena, John Druce, John A. Kilner, and Tatsumi Ishihara. "Relating surface chemistry and oxygen surface exchange in LnBaCo2O5+δ air electrodes." Faraday Discussions 182 (2015): 145–57. http://dx.doi.org/10.1039/c5fd00027k.

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The surface and near-surface chemical composition of electroceramic materials often shows significant deviations from that of the bulk. In particular, layered materials, such as cation-ordered LnBaCo2O5+δ perovskites (Ln = lanthanide), undergo surface and sub-surface restructuring due to the segregation of the divalent alkaline-earth cation. These processes can take place during synthesis and processing steps (e.g. deposition, sintering or annealing), as well as at temperatures relevant for the operation of these materials as air electrodes in solid oxide fuel cells and electrolysers. Furthermore, the surface segregation in these double perovskites shows fast kinetics, starting at temperatures as low as 400 °C over short periods of time and leading to a decrease in the transition metal surface coverage exposed to the gas phase. In this work, we use a combination of stable isotope tracer labeling and surface-sensitive ion beam techniques to study the oxygen transport properties and their relationship with the surface chemistry in ordered LnBaCo2O5+δ perovskites. Time-of-Flight Secondary-Ion Mass Spectrometry (ToF-SIMS) combined with 18O isotope exchange was used to determine the oxygen tracer diffusion (D*) and surface exchange (k*) coefficients. Furthermore, Low Energy Ion Scattering (LEIS) was used for the analysis of the surface and near surface chemistry as it provides information from the first mono-atomic layer of the materials. In this way, we could relate the compositional modifications (e.g. cation segregation) taking place at the electrochemically-active surface during the exchange at high temperatures and the oxygen transport properties in double perovskite electrode materials to further our understanding of the mechanism of the surface exchange process.
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Studer, M. S., R. T. W. Siegwolf, M. Leuenberger, and S. Abiven. "Multi-isotope labelling of organic matter by diffusion of <sup>2</sup>H/<sup>18</sup>O-H<sub>2</sub>O vapour and <sup>13</sup>C-CO<sub>2</sub> into the leaves and its distribution within the plant." Biogeosciences 12, no. 6 (March 20, 2015): 1865–79. http://dx.doi.org/10.5194/bg-12-1865-2015.

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Abstract. Isotope labelling is a powerful tool to study elemental cycling within terrestrial ecosystems. Here we describe a new multi-isotope technique to label organic matter (OM). We exposed poplars (Populus deltoides × nigra) for 14 days to an atmosphere enriched in 13CO2 and depleted in 2H218O. After 1 week, the water-soluble leaf OM (δ13C = 1346 ± 162‰) and the leaf water were strongly labelled (δ18O = −63 ± 8, δ2H = −156 ± 15‰). The leaf water isotopic composition was between the atmospheric and stem water, indicating a considerable back-diffusion of vapour into the leaves (58–69%) in the opposite direction to the net transpiration flow. The atomic ratios of the labels recovered (18O/13C, 2H/13C) were 2–4 times higher in leaves than in the stems and roots. This could be an indication of the synthesis of more condensed compounds in roots and stems (e.g. lignin vs. cellulose) or might be the result of O and H exchange and fractionation processes during phloem transport and biosynthesis. We demonstrate that the three major OM elements (C, O, H) can be labelled and traced simultaneously within the plant. This approach could be of interdisciplinary interest in the fields of plant physiology, palaeoclimatic reconstruction or soil science.
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Dissertations / Theses on the topic "18-O isotope exchange"

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Hendry, Garth S., and Garth Hendry@baldwins com. "Dependence of substrate-water binding on protein and inorganic cofactors of photosystem II." The Australian National University. Research School of Biological Sciences, 2002. http://thesis.anu.edu.au./public/adt-ANU20041124.140348.

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The photosynthetic water oxidation reaction is catalyzed by an inorganic Mn4OxCaClyHCO3-z cluster at the heart of the oxygen evolving complex (OEC) in photosystem II. In the absence of an atomic resolution crystal structure, the precise molecular organization of the OEC remains unresolved. Accordingly, the role of the protein and inorganic cofactors of PSII (Ca2+, HCO3- and Cl-) in the mechanism of O2-evolution await clarification. In this study, rapid 18O-isotope exchange measurements were applied to monitor the substrate-water binding kinetics as a function of the intermediate S-states of the catalytic site (i.e. S3, S2 and S1) in Triton X-100 solubilized membrane preparations that are enriched in photosystem II activity and are routinely used to evaluate cofactor requirements. Consistent with the previous determinations of the 18O exchange behavior in thylakoids, the initial 18O exchange measurements of native PSII membranes at m/e = 34 (which is sensitive to the 16O18O product) show that the ‘fast’ and ‘slowly’ exchanging substrate-waters are bound to the catalytic site in the S3 state, immediately prior to O2 release. Although the slowly exchanging water is bound throughout the entire S-state cycle, the kinetics of the fast exchanging water remains too fast in the S2, S1 [and S0] states to be resolved using the current instrumentation, and left open the possibility that the second substrate-water only binds to the active site after the formation of the S3 state. Presented is the first direct evidence to show that fast exchanging water is already bound to the OEC in the S2 state. Rapid 18O-isotope exchange measurements for Ex-depleted PSII (depleted of the 17- and 23-kDa extrinsic proteins) in the S2 state reveals a resolvable fast kinetic component of 34k2 = 120 ± 14 s-1. The slowing down of the fast phase kinetics is discussed in terms of increased water permeation and the effect on the local dielectric following removal of the extrinsic subunits. In addition, the first direct evidence to show the involvement of calcium in substrate-water binding is also presented. Strontium replacement of the OEC Ca2+-site reveals a factor of ~3-4 increase in the 18O exchange of the slowly exchanging water across the S3, S2 and S1 states while the kinetics of the fast exchanging water remain unchanged. Finally, a re-investigation of the proposed role for bicarbonate as an oxidizable electron donor to photosystem II was unable to discern any 18O enrichment of the photosynthetically evolved O2 in the presence of 18O-bicarbonate. A working model for O2-evolution in terms of these results is presented.
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Hendry, Garth S. "Dependence of substrate-water binding on protein and inorganic cofactors of photosystem II." Phd thesis, 2002. http://hdl.handle.net/1885/47151.

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The photosynthetic water oxidation reaction is catalyzed by an inorganic Mn4OxCaClyHCO3-z cluster at the heart of the oxygen evolving complex (OEC) in photosystem II. In the absence of an atomic resolution crystal structure, the precise molecular organization of the OEC remains unresolved. Accordingly, the role of the protein and inorganic cofactors of PSII (Ca2+, HCO3- and Cl-) in the mechanism of O2-evolution await clarification. In this study, rapid 18O-isotope exchange measurements were applied to monitor the substrate-water binding kinetics as a function of the intermediate S-states of the catalytic site (i.e. S3, S2 and S1) in Triton X-100 solubilized membrane preparations that are enriched in photosystem II activity and are routinely used to evaluate cofactor requirements. Consistent with the previous determinations of the 18O exchange behavior in thylakoids, the initial 18O exchange measurements of native PSII membranes at m/e = 34 (which is sensitive to the 16O18O product) show that the ‘fast’ and ‘slowly’ exchanging substrate-waters are bound to the catalytic site in the S3 state, immediately prior to O2 release. Although the slowly exchanging water is bound throughout the entire S-state cycle, the kinetics of the fast exchanging water remains too fast in the S2, S1 [and S0] states to be resolved using the current instrumentation, and left open the possibility that the second substrate-water only binds to the active site after the formation of the S3 state. Presented is the first direct evidence to show that fast exchanging water is already bound to the OEC in the S2 state. Rapid 18O-isotope exchange measurements for Ex-depleted PSII (depleted of the 17- and 23-kDa extrinsic proteins) in the S2 state reveals a resolvable fast kinetic component of 34k2 = 120 ± 14 s-1. The slowing down of the fast phase kinetics is discussed in terms of increased water permeation and the effect on the local dielectric following removal of the extrinsic subunits. In addition, the first direct evidence to show the involvement of calcium in substrate-water binding is also presented. Strontium replacement of the OEC Ca2+-site reveals a factor of ~3-4 increase in the 18O exchange of the slowly exchanging water across the S3, S2 and S1 states while the kinetics of the fast exchanging water remain unchanged. Finally, a re-investigation of the proposed role for bicarbonate as an oxidizable electron donor to photosystem II was unable to discern any 18O enrichment of the photosynthetically evolved O2 in the presence of 18O-bicarbonate. A working model for O2-evolution in terms of these results is presented.
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Book chapters on the topic "18-O isotope exchange"

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Gizhevskii, B. A., A. Ya Fishman, E. A. Kozlov, T. E. Kurennykh, S. A. Petrova, I. Sh Trakhtenberg, E. V. Vykhodets, V. B. Vykhodets, and R. G. Zakharov. "Oxygen Isotope Exchange between Gaseous Phase Enriched with 18O Isotope and Nanocrystal Oxides LaMnO3+δ Obtained by Severe Plastic Deformation." In Diffusion in Solids and Liquids III, 233–38. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-51-5.233.

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Bianchi, Thomas S., and Elizabeth A. Canuel. "Stable Isotopes and Radiocarbon." In Chemical Biomarkers in Aquatic Ecosystems. Princeton University Press, 2011. http://dx.doi.org/10.23943/princeton/9780691134147.003.0003.

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This chapter discusses the basic principles surrounding the application of stable isotopes in natural ecosystems, which are based on variations in the relative abundance of lighter isotopes from chemical rather than nuclear processes. Due to faster reaction kinetics of the lighter isotope of an element, reaction products in nature can be enriched in the lighter isotope. These fractionation processes can be complex, but have proven to be useful in determining geothermometry and paleoclimatology, as well as sources of organic matter in ecological studies. The most common stable isotopes used in oceanic and estuarine studies are 18O, 2H, 13C, 15N, and 34S. The preference for using such isotopes is related to their low atomic mass, significant mass differences in isotopes, covalent character in bonding, multiple oxidations states, and sufficient abundance of the rare isotope. Living plants and animals in the biosphere contain a constant level of 14C, but when they die there is no further exchange with the atmosphere and the activity of 14C decreases with a half-life of 5730 ± 40 yr; this provides the basis for establishing the age of archeological objects and fossil remains.
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