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This material had an anomalously high 13 C: 12 C ratio (0.0112372 [4]), and was established as δ 13 C value of zero. Since the original PDB specimen is no longer available, its 13 C: 12 C ratio can be back-calculated from a widely measured carbonate standard NBS-19, which has a δ 13 C value of +1.95‰. [ 5 ]
The δ 13 C of C3 plants depends on the relationship between stomatal conductance and photosynthetic rate, which is a good proxy of water use efficiency in the leaf. [19] C3 plants with high water-use efficiency tend to be less fractionated in 13 C (i.e., δ 13 C is relatively less negative) compared to C3 plants with low water-use efficiency. [19]
The ratio of carbon-13 and carbon-12 isotopes in these types of plants is as follows: [11] C 4 plants: −16‰ to −10‰ CAM plants: −20‰ to −10‰ C 3 plants: −33‰ to −24‰ Limestones formed by precipitation in seas from the atmospheric carbon dioxide contain normal proportion of 13 C.
Carbon-13 has a non-zero spin quantum number of 1 / 2 , and hence allows the structure of carbon-containing substances to be investigated using carbon-13 nuclear magnetic resonance. The carbon-13 urea breath test is a safe and highly accurate diagnostic tool to detect the presence of Helicobacter pylori infection in the stomach. [ 4 ]
One of these, the standard for normalizing δ 13 C values, is Pee Dee Belemnite (PDB), a fossil which has a 13 C / 12 C ratio of 1.12372%. [3] δ 13 C for some sample is then calculated by dividing the amount of 13 C by 1.12372% and then subtracting 1 and multiplying by 1000 to give a value in "per mil". [4] A related standard is the use of a ...
C and 13 C are measured, and the resulting 13 C / 12 C ratio is then compared to a standard ratio known as PDB. (The 13 C / 12 C ratio is used because it is much easier to measure than the 14 C / 12 C ratio, and the 14 C / 12 C ratio can be easily derived from it.) The resulting value, known as δ 13 C, is calculated as follows: [9]
If an animal (or human) eats only C3 plants, their δ 13 C values will be from −18.5 to −22.0‰ in their bone collagen and −14.5‰ in the hydroxylapatite of their teeth and bones. [ 16 ] In contrast, C4 feeders will have bone collagen with a value of −7.5‰ and hydroxylapatite value of −0.5‰.
Fry found that at the beginning of the study the shrimp had isotopic values of δ 13 C = -11 to -14‰ and 6-8‰ for δ 15 N and δ 34 S. As the shrimp matured and migrated offshore, the isotopic values changed to those resembling offshore organisms (δ 13 C= -15‰ and δ 15 N = 11.5‰ and δ 34 S = 16‰). [18]