Isotopic ratios of carbon

The values of E(t) so computed are listed in Table 4. The correction for fractionation of carbon dioxide at the sea surface is a serious one. It makes the interpretation of 13C/12C variations in wood difficult and militates against the use of the isotope ratio of carbon as a thermometer. This correction, when applied to variations of carbon-14 in wood, is able to explain the Suess radiocarbon "wiggles" of about 100 years duration each, without the need to invoke changes in the neutron flux from the sun [54]. 

Sakai H, Casadevall TJ, Moore JG (1982) Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano, Hawaii. Geochim Cosmochim Acta 46 729-738 Sakai H, DesMarais DJ, Ueda A, Moore JG (1984) Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts. Geochim Cosmochim Acta 48 2433-2441 Sano Y, Marty B (1995) Origin of carbon in fumaroUc gas from island arcs. Chem Geol 119 265-274... 

Naturally-occurring products are being examined also for different isotopic ratios of carbon. Water from various sources are known to vary in density up to ten parts per million. These differences are due chiefly to the different ratios of oxygen isotopes, and in part to the different deuterium ratios. 

In carbon dating, the relative amounts of carbon isotopes are compared. Since carbon isotopes decay at a regular rate, this information can be used to find the age of carbon compounds. However, the isotopic ratios of carbon on this planet are different from those on Earth. The isotopic ratios of carbon on this planet are 80.2 % 12C, 19.3% 13C, and 0.5% 14C. 

Because the variations in the actual isotopic ratio of carbon are very smalls results are reported u delta notation or parts per thousand variation in the ratio from that of the PDB... 

Lipids form a minor part of the carbon content of herbivore diets As a result, despite the fact that they are used primarily for energy metabolism, their abundance is not sufficient to greatly influence the isotopic composition of blood bicarbonate For this reason, the isotopic composition of lipids will not significantly affect the isotopic ratio of carbon in bone apatite ... 

Consequently, under normal trade wind conditions there is a secondary maximum of atmospheric CO2 in the neighborhood of the equator in the eastern Tropical Pacific (Figure 8). That this is due to an influx of oceanic CO2 to the atmosphere and not to tropical deforestation is clearly shown by the isotopic ratio of carbon 13 to carbon 12, which increases continuously from high northern latitudes where fossil fuel CO2 which, like the CO2 of the land biota, is low in carbon 13, enters the atmosphere, to about 20 south latitude. 

Sakai H., Desmarais D. J., Uyeda A., and Moore J. G. (1984) Concentration and isotope ratios of carbon nitrogen and sulfur in ocean floor basalts. Geochim. Cosmochim. Acta 48, 2433 - 2441. 

Gamo T., Tsutsumi M., Sakai H., Nakazawa T., Tanaka M., Honda H., and Kubo H. (1989) Carbon and oxygen isotopic ratios of carbon dioxide of a stratospheric profile over Japan. Tellus 41B, 127-133. 

Equations 3 and 4 are recommended to determine the Site-specific Isotope Ratios of carbon, since the existence of differential residual Nuclear Overhauser Enhancements in vanillin samples doped with Cr(AcAc)3 may induce more or less significant bias. 

Natural radioactivity is useful in establishing the approximate age of objects of archaeological, anthropological, or historical interest. Radiocarbon dating is the estimation of the age of objects through measurement of isotopic ratios of carbon. 

After chemical pretreatment, the samples are burnt to produce carbon dioxide and nitrogen. A small amount of this gas is bled into a mass spectrometer, where the stable isotope ratios of carbon and nitrogen are measured. These ratios provide useful information on the purity of the sample and clues about the diet and climatic conditions of the living organism. The carbon isotope ratio is also used to correct for isotopic fractionation in the radiocarbon measurement. The carbon dioxide is collected in a glass ampoule or converted to graphite for radiocarbon measurement on the AMS system. 

Isotopic abundances can be determined with isotope ratio mass spectrometry (IRMS), an instrument described in Chapter 5. To analyze the stable isotope ratios of carbon and oxygen, the instrumental procedure incorporates a conversion of all organic carbon to CO2, followed by the introduction of that compound into the mass spectrometer. The fragments of interest have amu s of 44 ( 2)/ 45 ( C 2 and and 46 ( 2c 0 D, and 2c 02). ... 

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