Nitrogen reservoirs isotopes

The most abundant isotope is which constitutes almost 99% of the carbon in nature. About 1% of the carbon atoms are There are, however, small but significant differences in the relative abundance of the carbon isotopes in different carbon reservoirs. The differences in isotopic composition have proven to be an important tool when estimating exchange rates between the reservoirs. Isotopic variations are caused by fractionation processes (discussed below) and, for C, radioactive decay. Formation of takes place only in the upper atmosphere where neutrons generated by cosmic radiation react with nitrogen ... 

Schematic diagram of the stable nitrogen isotope ratios of different nitrogen reservoirs in the sea. The general range of stable isotope ratios (with respect to the atmosphere) found in nature is given in the boxes and the difference fractionation factors e (in %o) accompany arrows between the boxes. Many of the values are approximations because of the wide variations of observations. See Table 5.3 for more details of some of the reactions and the text for explanation. Values are based on data presented by Altabet and Small (1990), Altabet and Francois (1994) and Sigman and Casciotti (2001).

Nitrogen in atmospheric air has a very homogeneous isotope composition. The atmosphere is the main nitrogen sink and the largest terrestrial nitrogen reservoir. NSVEC is the reference material initially prepared by Jung and Svec, Iowa State... 

Figure 2.12 gives an overview about the nitrogen isotope variations in some important reservoirs. 

Schoenberg R, Zink S, Staubwasser M, von Blanckenburg F (2008) The stable Crisotope inventory of solid Earth reservoirs determined by double-spike MC-ICP-MS. Chem Geol 249 294-306 Schoenheimer R, Rittenberg D (1939) Studies in protein metabolism I, General considerations in the application of isotopes to the study of protein metabolism. The normal abundance of nitrogen isotopes in amino acids, J Biol Chem 127 285-290... 

The nitrogen isotopic composition of the upper mantle has been estimated from MORE (Marty and Humbert, 1997 Marty and Zimmermann, 1999) and diamond (Javoy et ai, 1984 Cartigney et ai, 1998 Eoyd and Pillinger, 1994) data to be approximately = —4%c. Values as low as 515N = —25%o have been found in diamonds, indicating that there is another reservoir in the mantle. 

FIGURE 5.3 Outline of the deep nitrogen cycle in the modern Earth. The size of the reservoirs is taken mainly from Miyazaki et al. (2004) and is in mols. The nitrogen isotope values are from Marty and Dauphas (2003) and the fluxes are from Fischer et al. (2002) and are in mol/yr. 

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