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Isotope fractionation occurs during a phase transition, when the ratio of light to heavy isotopes in the involved molecules changes. When water vapor condenses (an equilibrium fractionation), the heavier water isotopes (18 O and 2 H) become enriched in the liquid phase while the lighter isotopes (16 O and 1 H) tend toward the vapor phase. [1]
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope-ratio mass spectrometry , and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between ...
An isoscape is a geologic map of isotope distribution. It is a spatially explicit prediction of elemental isotope ratios (δ) that is produced by executing process-level models of elemental isotope fractionation or distribution in a geographic information system (GIS).
Equilibrium isotope fractionation is the partial separation of isotopes between two or more substances in chemical equilibrium. Equilibrium fractionation is strongest at low temperatures, and (along with kinetic isotope effects) forms the basis of the most widely used isotopic paleothermometers (or climate proxies): D/H and 18 O/ 16 O records from ice cores, and 18 O/ 16 O records from calcium ...
The difference is whether the relative abundance is with respect to all the nitrogen, i.e. 14 N plus 15 N, or just to 14 N. Since the atmosphere is 99.6337% 14 N and 0.3663% 15 N, a is 0.003663 in the former case and 0.003663/0.996337 = 0.003676 in the latter.
Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
Nitrogen-15 is a rare stable isotope of nitrogen. Two sources of nitrogen-15 are the positron emission of oxygen-15 [8] and the beta decay of carbon-15. Nitrogen-15 presents one of the lowest thermal neutron capture cross sections of all isotopes. [9] Nitrogen-15 is frequently used in NMR (Nitrogen-15 NMR spectroscopy).
Figure 2 Figure 3 - Isotopic Fractionation Sources. The atoms hydrogen, oxygen, and carbon co-exist naturally in specific proportions with their stable isotopes, 2H (or D), 18O and 13C respectively, in different proportions as shown in the figure 2 below. The amount and distribution of the different isotopes in a molecule is influenced by: [5]