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23 paź 2020 · Carbon isotopes, 14 C and 13 C, in atmospheric CO 2 are changing in response to fossil fuel emissions and other human activities. Future simulations using different SSPs show continued changes in isotopic ratios that depend on fossil fuel emissions and, for 13 C, BECCS.
Stable carbon isotopes in carbon dioxide are utilized differentially by plants during photosynthesis.
Isotopes are different forms of an element that have the same number of protons but a different number of neutrons. Some elements—such as carbon, potassium, and uranium—have naturally occurring isotopes. Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 (six protons and six neutrons).
For instance, the 6 proton carbon atom has three stable, naturally occurring isotopes: carbon-12 ([latex]\ce{_{6}^{12}C}[/latex]), carbon-13 ([latex]\ce{_{6}^{13}C}[/latex]) and carbon-14 ([latex]\ce{_{6}^{14}C}[/latex]), weighing 12, 13 and 14 amu respectively.
C3 plants are noticeably deficient in heavy isotopes of carbon. C4 CO 2 molecules incorporated into the four carbon compounds oxaloacetate and malate; A newer form of carbon fixation that arose 65 million years ago.
The isotopic compo-sition of organic compounds is primarily dependent on the isotopic composition of the precursor molecules and on isotope fractionation during (bio)synthesis or (bio)degradation reactions.
Most elements on the periodic table have at least two stable isotopes. For example, in addition to C12 C 12, a typical sample of carbon contains 1.11% C 613 C 6 13, with 7 neutrons and 6 protons, and a trace of C 614 C 6 14, with 8 neutrons and 6 protons.
