Isotopes oxygen

Oxygen-18 was first produced commercially at the Weizmann Institute in Israel from the distillation of water [54] and this method has subsequently been 

At the Nuclear Research Centre at Karlsruhe (FRG) oxygen-17 and -18 are separated by distillation of heavy water. This work, which is carried out in collaboration with Norsk—Hydro, capitalises on the fact that there is enrichment of the heavy oxygen isotopes in the Norwegian manufacture of heavy water [23]. In this plant, the features of which have been described [56], oxygen-18 is produced at 99.9 atom%. Intermediate product is converted into H2O and fed to a distillation unit in order to produce useful enrichments of oxygen-17 (approaching 30 atom%). Water- 0 (depleted in both and 0) is produced at 99.99 atom% 0 [56]. 

The separation of oxygen-16, -17 and -18 by cryogenic distillation of nitric oxide is used at Los Alamos (USA) and has been referred to in the previous section on the separation of nitrogen isotopes. 

Cryogenic distillation of oxygen is an effective method of producing oxygen-18 economically at lower enrichments (25 atom%). The method is limited by the fact that oxygen-18 in the feedstock is present as 0 0. By randomisation of the molecular species, for example by heating, higher enrichments could be attained [26]. The technique provides a ready source of depleted material ( O2). 

Cryogenic distillation of oxygen is an effective method of producing oxygen-18 economically at lower enrichments (25 atom%). The method is limited by the fact that oxygen-18 in the feedstock is present as By randomisation 

Oxygen isotopes have been the most thoroughly studied isotopes in carbonate mineral systems. There are three stable isotopes of oxygen 160 = 99.763%, 170 = 0.0375% and 180 = 0.1995% (Garlick, 1969). The fractionation of 180 relative to 160 is commonly measured and reported as the value of 8180 relative to a standard. Two standards have been widely used in reporting 8180 values. The most common one in general usage now is SMOW, which stands for standard mean ocean water. 

It has an I80 / 160 ratio of 2005.20 ( 0.45) x 106 (Baertschi, 1976). In many studies involving carbonates, PDB is the standard relative to which values are reported. The PDB standard is based on the oxygen isotope ratio of a Cretaceous belemnite from the Peedee formation in South Carolina. Because it was composed of calcite, many limestones have isotopic ratios close to it. Values ( X ) reported relative to the two standards are related by equation 3.16. 

One of the most important uses of oxygen isotopes in carbonates is as geothermometers. Isotope fractionation is pressure independent (Clayton et al., 1975), giving it an advantage over other geothermometers which are generally both temperature and pressure dependent. The equation for calculating the temperature at which calcite precipitates from water is  

Oxygen isotopes are used in archaeology primarily to study ancient environments and to examine past human mobility. Isotope measurements are always reported as a ratio of one isotope to another, lighter and more common cousin. Ratios are used in order to standardize the value that is reported, regardless of the amount of material measured or the concentration of the element present. 

The ratio of oxygen isotope 18 to oxygen isotope 16 is often used to measure past climate because it is directly related to atmospheric temperature. Oxygen isotopes are used as a proxy for temperature in studies of marine sediments, ice cores, faunal remains, and other materials. The abundance of the two isotopes depends on temperature-related fractionation processes such as evaporation, condensation, and transpiration. 

During evaporation at the ocean s surface, the lighter isotope, O, is preferentially released into the atmosphere because of its higher vapor pressure (Fig. 4.15). As moisture-laden clouds move inland, the heavier isotope ( O) precipitates preferentially and rain clouds become progressively depleted in as they move inland. Polar and inland rain is lighter than tropical and coastal rain summer precipitation is less depleted than winter precipitation. Since condensation is also dependent on temperature, further depletion of occurs at higher elevations and latitudes. Evaporation of 

Oxygen isotopes in ancient human skeletal remains are found in both bone and tooth enamel. Samples for the analysis of human skeletal remains are normally taken from dental enamel due to conditions of preservation and resistance to diagenesis. The hydroxyapatite mineral, a primary component of enamel, contains oxygen, in both phosphate groups (POp and carbonates (CO ). Phosphate and carbonate produce comparable results for oxygen isotope ratios, but less sample is needed for carbonate, preparation is less demanding, and results between laboratories are more comparable. 

The oxygen isotopes of terrestrial materials mostly fall along with what is termed a mass-fractionation line (MFL). The MFL is defined by a slope of 0.5 passing through VSMOW as shown in Fig. 4.5. The oxygen isotopic composition is unique for different types of meteorites, which are broadly classified as chondrites and achondrites. 

In Fig. 4.6 the oxygen isotopic composition of these two meteoritic types are compared. The bulk oxygen isotopic composition of various groups of achondrites 

Most non-chondrule solids in the inner Solar System experienced thermal processing (see Chapter 8) that could have modified their initial oxygen isotopic composition (Yurimoto Kuramoto 2004). The complicated structure of meteoritic oxygen isotopes is difficult to reproduce simply by physical mixing of different reservoirs. Apart from thermal processing (e.g. melting, vaporization, condensation), a large mass-independent chemical process is required. The exact mechanism for this likely photochemical process is yet unknown, but the available constraints leave only a few pathways open. 

13C and 180 atomic signatures observed by radio astronomers (Glassgold et al. 1985 van Dishoeck Black 1988 Langer Penzias 1990 Sheffer et al. 2002 Dartois etal. 2003 Pietu etal. 2007) and anomalous meteoritic S15N composition (Thiemens Heidenreich 1983 Clayton 2002). 

17 nm is one of the most effective lines for the C180 dissociation, responsible for 58% of its destruction (van Dishoeck Black 1988). 

The isotope eomposition of oxygen in the Cenozoic lavas of Antarctica, measured by Wenner (1974), are mostly in the normal range for mantle-derived volcanic rocks (i.e., = -h5.0 to -h6.5%o relative to 

Quartz and feldspar of a granite inclusion in basalt (5 0 5.2%o) are strongly depleted in with 

518O = -4.4%o (feldspar) and -8.6%o (quartz). All of these results are consistent with the current state of knowledge of the oxygen isotope composition of igneous rocks (Taylor 1968 Anderson et al. 1971 Faure 1986 Hoefs 1997 Valley and Cole 2001 Sharp 2007). 

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In a similar vein, mean seawater temperatures can be estimated from the ratio of 0 to 0 in limestone. The latter rock is composed of calcium carbonate, laid down from shells of countless small sea creatures as they die and fall to the bottom of the ocean. The ratio of the oxygen isotopes locked up as carbon dioxide varies with the temperature of sea water. Any organisms building shells will fix the ratio in the calcium carbonate of their shells. As the limestone deposits form, the layers represent a chronological description of the mean sea temperature. To assess mean sea temperatures from thousands or millions of years ago, it is necessary only to measure accurately the ratio and use a precalibrated graph that relates temperatures to isotope ratios in sea water. 

Eig. 4. The bulk oxygen isotopic composition of different meteorite classes where (—) is the terrestial fractionation line. The 5 notation refers to the normalized difference between or ratios to those in standard mean ocean water (SMOW) in relative units of parts per thousand. The... 

Let us fix attention on a particular H20 molecule A in the interior of water (if we wish to identify this molecule we can suppose that it contains a nucleus of the oxygen isotope 01S) and let us consider the water molecules which happen to be nearest neighbors of this molecule at the moment. These molecules have been in contact with A for different lengths of time. Since all the molecules in the liquid wander about, there was a time when none of these molecules was in contact with A. Further, if we could now begin to watch these molecules, we should find that, after the lapse of different periods of time, they become separated from A and each is replaced by another molecule. Similar remarks can be made about the molecules which come into contact with any chosen molecule. We can now raise the question—-What is the rate of turnover of this process The rate depends on the degree of local order and disorder, which in turn depends on the strength and character of the forces between adjacent molecules. 

Samuel, D. (1962). Methodology of oxygen isotopes. In Hayaishi, O. (ed.), Oxygenases, pp. 31-86. Academic Press, New York. 

Fig. 21. Raman spectra showing improvement of signal-to-noise using multiple scans with computer time averaging over single scan. Lower traces single scan upper traces multiple scans (10 scans) and computer output, (a) i of CCU (b) Hg emission line and n of LiCh (c) n of Na02 with oxygen isotopic counterparts (89).

V.A. Sobyanin, V.I. Sobolev, V.D. Belyaev, O.A. Mar ina, A.K. Demin, and A.S. Lipilin, On the origin of the Non-Faradaic electrochemical modification of catalytic activity (NEMCA) phenomena. Oxygen isotope exchange on Pt electrode in cell with solid oxide electrolyte, Catal. Lett. 18, 153-164 (1993). 

These four PET scans show how blood flow to different parts of the brain is affected by various activities. In this case, an oxygen isotope that is taken up by the hemoglobin in blood is used as a source of positrons. 

Fig. 18-1 Benthic foraminiferal oxygen isotope record from 3477 m water depth in the eastern tropical Pacific ocean from Ocean Drilling Program site 677 (Shackleton et al, 1990). ratios are expressed in the S...

Fig. 18-13 High-resolution measurements of CO2 over the last glacial-interglacial transition from the Byrd ice core in west Antarctica (Neftel et ai, 1982). Also plotted is the oxygen isotope record temperature proxy from the Byrd core (Johnsen et ai, 1972). The time scale for the records plotted here is from Sowers and Bender (1995).

Grootes, P. M., Stuiver, M., White, J. W. C. et al. (1993). Comparison of oxygen isotope records from the GISP2 and GRIP Greenland ice cores. Nature 366, 552-554. 

Johnsen, S. J., Dansgaard, W., Clausen, H. B., and Langway, C. C. (1972). Oxygen isotope profiles through the Antarctic and Greenland ice sheets. Nature 235,429-434. 

Shackleton, N. J. (1967). Oxygen isotope analyses and Pleistocene temperatures re-assessed. Nature 215, 15-17. 

Marino, B.D. and DeNiro, M.J. 1987 Isotopic analysis of archaeobotanicals to reconstruct past climates Effects of activities associated with food preparation on carbon, hydrogen and oxygen isotope ratios of plant cellulose. Journal of Archaeological Science 14 537-548. 

Wright, L.E. and Schwarcz, HP. 1998 Stable carbon and oxygen isotopes in human tooth enamel identifying breastfeeding and weaning in prehistory. American Journal of Physical Anthropology 106 1-18. 

Bryant, J.D., Luz, B. and Froelich, P.N. 1994 Oxygen isotopic composition of fossil horse tooth phosphate as a record of continental paleoclimate. Palaeogeography, Palaeoclimatology, Palaeoecology 107 303-316. 

In parallel developments, oxygen isotope studies based on the stable phosphate ion in calcified tissues have been found to be more successful using enamel than bone as sample material (Ayliffe et al. 1994 Bryant et al 1994), and similarly oxygen isotopes from the less stable C—0 bond in enamel carbonate seems to be more predictable (Bocherens et al. 1996). Researchers exploring the relationship between Electron Spin Resonance (ESR) and carbonate content in enamel have found that dates are mostly consistent when carbonate levels did not deviate much from biogenic levels (Grun et al. 1990 Rink and Schwarcz 1995). 

Ayliffe, L.K., Chivas, A.R. and Leakey, M.G. 1994 The retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate. Geochimica et Cosmochimica Acta 58 5291-5298. 

Quade, J., Cerling, T.E., Barry, J.C., Morgan, M.E., Pilbeam, D.E., Chivas, A.R., Lee-Thorp, J.A. and van der Merwe, N.J. 1992 A 16-Ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from Pakistan. Chemical Geology (Isotope Geoscience) 94 183-192. 

Tooth Oxygen Isotope Ratios As Paleoclimate Monitors In Arid Ecosystems... 

Some fifty years ago, a classic theoretical paper (Urey 1947) proposed that the oxygen isotope ratio ( 0/ 0) in various minerals depends on two variables the local environmental temperature and the oxygen isotopic ratio in the environmental water. The proposal was verified experimentally in carbonates (Epstein et al. 1951, 1953 McCrea 1950) where the oxygen isotope ratio is dependent on the temperature of formation and the ratio in... 

Suggestions that phosphatic minerals in mammals could be used, however, revived the interest in climate reconstruction in continental interiors. Aquatic, cold-blooded animals like fish have body temperatures and body water oxygen isotopic compositions that are directly dependent on the water in which they live. For these animals, a commonly used equation describes the relationships among temperature, water oxygen isotopic composition and phosphate oxygen isotopic composition as (Longinelli and Nuti 1973 verified by Kolodny et al. 1983, among others) ... 

Oxygen isotope ratios are presented in permit (%o) using the d notation... 

Body water oxygen isotopic composition in mammals is a function of the oxygen mass balance of the specific animal. In general, it can be related to three major oxygen sources air oxygen, drinking water, and food (both the... 

Figure 6.4. Percent average humidity compared with 6 0 in bone phosphate. The strong association between the two variables across the species of Australian marsupials (data from Ayliffe and Chivas 1990) and North American white-tailed deer (data from Luz ei a/. 1990) indicates that their body water oxygen isotopic composition is strongly determined by the 8"0 in their diet since plant 8 0 varies in negative correlation with humidity.

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