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chemical property > carbon isotope ratio

Preferred term

carbon isotope ratio  

Definition

  • Carbon isotope ratios are useful principally to distinguish between marine and terrestrial organic matter sources in sediments and to identify organic matter from different types of land plants. The stable carbon isotopic composition of organic matter reflects the isotopic composition of the carbon source as well as the discrimination (fractionation) between 12C and 13C during photosynthesis. Most plants, including phytoplankton, incorporate carbon into their biomass using the Calvin (C3) pathway, which discriminates against 13C to produce a shift in δ13C values of about −20‰ from the isotope ratio of the inorganic carbon source. Organic matter produced from atmospheric carbon dioxide (δ13C ≈ −7‰) by land plants using the C3 pathway (including almost all trees and most shrubs) has an average δ13C value of approximately −27‰. Marine algae use dissolved bicarbonate, which has a δ13C value of approximately 0‰. As a consequence, marine organic matter typically has δ13C values varying between −18‰ and −22‰. The “typical” difference of about 7‰ between organic matter of marine primary producers and land plants has been used successfully to trace the sources and distributions or organic matter in coastal sediments. Unlike C/N ratios, δ13C values are not significantly influenced by sediment texture, making them useful in reconstructing past sources of organic matter in changing depositional conditions. (Adapted from: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/carbon-isotope-ratio)

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http://data.loterre.fr/ark:/67375/QX8-3MRC3MN6-F

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