Isotopes of nitrogen

Birds and animals are tagged so that their wanderings and ultimate fate can be followed. To do the same for nitrogen fertilizer, we use the heavy isotope of nitrogen, as a tag or label . This is a safe isotope to use because it is not radioactive. The of the label is taken up by the crop, incorporated in the soil s... 

Unstable isotopes decompose (decay) by a process referred to as radioactivity. Ordinarily the result is the transmutation of elements the atomic number of the product nucleus differs from that of the reactant. For example, radioactive decay of produces a stable isotope of nitrogen, N. The radiation given off (Figure 2.6) may be in the form of—... 

A smaller number of individuals, 132 samples, was analyzed for stable isotopes of nitrogen. There were two objectives to the nitrogen isotope analysis 1) to determine the amount of animal protein in the diet and to look for variation between the sexes and 2) to determine when infants were weaned from the breast. These objectives were addressed by selecting at least ten individuals, when available, from a number of age classes. Figure 1.1 illustrates the age distribution of the sample. Table 1.3 shows the results of these analyses. Individual 5 N values are provided in Herring et al. (1998). 

Figure 1.1. Age distribution of the samples analyzed for stable isotopes of nitrogen.

Sex and age differences in stable isotopes of nitrogen and carbon are not pronounced. There is no evidence that males and females were eating different foods and the only evidence for age differences, higher 8 N in infants, has been explained by the trophic level shift during the time the infant derives most of its protein from, breast milk. The small amount of variation in both and 5 N values supports the historical sources, which indicate that while food was plentiful, the diet was rather monotonous. 

Ambrose focuses on stable nitrogen isotope ratios and reports the results of controlled diet and climate experiments on rats. He explores trophic level differences and heat stress and their effects on stable isotopes of nitrogen. As with the preceding chapters by Schwarcz and Hedges and van Klinken, Ambrose explores the various biochemical principles that explain why variation is expected under these circumstances. 

C22-0113. One isotope of nitrogen and one isotope of fluorine are positron emitters with relatively long half-lives. 

The half-lives of the elements vary widely, as shown in Table 3.2. Some isotopes, nitrogen-14 for example, are stable and experience no natural radioactive decay. However, bombarding even a stable element with energetic alpha rays can cause transmutation. Rutherford discovered the proton when he created hydrogen from a stable isotope of nitrogen. 

Two of these isotopes, carbon-12, the most abundant, and carbon-13 are stable. Carbon-14, on the other hand, is an unstable radioactive isotope, also known as radiocarbon, which decays by the beta decay process a beta particle is emitted from the decaying atomic nucleus and the carbon-14 atom is transformed into an isotope of another element, nitrogen-14, N-14 for short (chemical symbol 14N), the most common isotope of nitrogen ... 

Also the stable isotopes of nitrogen, like those of carbon, are fractionated when nitrogen is incorporated into the plants. Determining the isotopic ratios between nitrogen-15 and nitrogen-14 in animal remains also reveals information on the diets of ancient animals and humans (White 1999 de Niro 1987). 

Naude, R. An isotope of nitrogen, mass 15. Phys. Rev. 34, 1498-1499 (1929). Note that Naude refers in this paper to two earlier communications by King and Birge (1930) on the discovery of 13C. 

ISOTOPES There are 19 isotopes of nitrogen, two of which are stable. The stable ones and their proportion to the natural abundance of nitrogen on Earth follow N-14 = 99.634% and N-15 = 0.366%. The other 17 isotopes are radioactive and man-made in nuclear reactors and have half-lives ranging from a few nanoseconds to 9.965 minutes. 

Since the alpha-ray impacts shattered only a minute proportion of the total number of atoms of boron, aluminum, or magnesium, the chemical identification of the products was extremely difficult. These indefatigable workers, however, accomplished even this. Although it would have been impossible to identify the products simply by ordinary chemical means, the Joliots were able to take advantage of the radioactive nature of the products formed. Since they had good reason to believe that the boron atom had captured a helion and ejected a neutron and that the new element was therefore probably an isotope of nitrogen, they heated some bombarded boron nitride with caustic soda and found that the liberated... 

Carbon-14 decays by emitting a beta particle, transforming it back into the most stable isotope of nitrogen. But it is in no hurry to do so the half-life of C is around 5,730 years. This time scale makes radiocarbon the ideal archaeologist s tool. 

Nitrogen-15, a readily available isotope of nitrogen, has a nuclear spin of and a somewhat larger magnetic moment. The two allowed orientations of / with respect to S produce a doublet hyperfine splitting. It is often easier to resolve the doublet produced by N than the triplet produced by N, and the resulting spectra are simpler and easier to interpret. 

The use of the stable isotope of nitrogen, 15N, to confirm and measure fixation ... 

Fisk, A.T., Moisey, J., Hobson, K.A., Karnovsky, N.J., Norstrom, R.J., 2001. Chlordane components and metabolites in seven species of Arctic seabirds from the Northwater Polynya relationships with stable isotopes of nitrogen and enantiomeric fractions of chiral components. Environ. Pollut. 113, 225-238. 

If we again refer to Table 6.1, we find that neither of the two isotopes of nitrogen is ideal for NMR. The most abundant isotope of nitrogen, 14N, which represents greater than 99% of nitrogen s natural abun-... 

The other isotope of nitrogen, l5N, also has an inherent low sensitivity, which, when multiplied by a very low natural abundance, leads to an extremely low absolute sensitivity. Modern instrumentation has largely overcome the problem of sensitivity (for labeled samples or by indirect detection) and we focus our attention on 15N largely because its spin number is one-half and its line-widths are quite narrow. 

Natural isotopes of nitrogen and their solar abundances... 

The theory of Kobozev is open to criticism of the character recently stated by Kummer and Emmett (184), who observed that there was a very rapid exchange between the isotopes of nitrogen in the presence of singly and doubly promoted iron synthetic ammonia catalyst. Kobozev (167) had concluded earlier that iron synthetic ammonia catalysts consisted of an ensemble of iron atoms to which were attached the promoter molecules. Each ensemble was capable of adsorbing only one nitrogen molecule further, in accordance with his theory, these ensembles, separated from one another by geometrical barriers, would make the... 

Two stable isotopes of nitrogen exist, (99.634%) and (0.366%). Because of this mass difference the heavier isotope reacts at a sHghtly slower rate, producing a kinetic isotope fractionation in many biological reactions. The increase in the in the reaction products is typically expressed as the parts per... 

Struck, U., Voss, M., and Bodungen, B. V. (1998). Stable isotopes of nitrogen in fossil cladoceran exoskeletons Imphcations for nitrogen sources in the central Baltic Sea during the past century. 

Wastewater nutrients and animal wastes are generally enriched in the heavy stable isotope of nitrogen (Sammarco et al., 1999 Heikoop et al., 2000). 

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