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The three major isotopes used in aquatic ecosystem food web analysis are 13 C, 15 N and 34 S. While all three indicate information on trophic dynamics, it is common to perform analysis on at least two of the previously mentioned three isotopes for better understanding of marine trophic interactions and for stronger results.
Sulfur has four stable isotopes, 32 S, 33 S, 34 S, and 36 S, of which 32 S is the most abundant by a large margin due to the fact it is created by the very common 12 C in supernovas. Sulfur isotope ratios are almost always expressed as ratios relative to 32 S due to this major relative abundance (95.0%).
Of the 26 "monoisotopic" elements that have only a single stable isotope, all but one have an odd atomic number—the single exception being beryllium. In addition, no odd-numbered element has more than two stable isotopes, while every even-numbered element with stable isotopes, except for helium, beryllium, and carbon, has at least three.
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear.
For indium and rhenium, the long-lived radionuclide is actually the most abundant isotope in nature, and the stable isotope is less abundant. In two additional cases ( bismuth [ 2 ] and protactinium ), mononuclidic elements occur which are not monoisotopic because the naturally occurring nuclide is radioactive, and thus the element has no ...
The 80 elements with one or more stable isotopes comprise a total of 251 nuclides that have not been shown to decay using current equipment. Of these 80 elements, 26 have only one stable isotope and are called monoisotopic. The other 56 have more than one stable isotope. Tin has ten stable isotopes, the largest number of any element.
Of the different isotopes that exist, one common classification is distinguishing radioactive isotopes from stable isotopes. Radioactive isotopes are isotopes that will decay into a different isotope. For example, 3 H is a radioactive isotope of hydrogen. It decays into 3 He with a half-life of ~12.3 years.
In order to study trace metal stable isotope biogeochemistry, it is necessary to compare the relative abundances of isotopes of trace metals in a given biological, geological, or chemical pool to a standard (discussed individually for each isotope system below) and monitor how those relative abundances change as a result of various biogeochemical processes.