Carbon-13(13C) is a natural,stableisotopeofcarbonwith anucleuscontaining 6protonsand 7neutrons. One of theenvironmental isotopes, it makes up about 1.1% of all natural carbon onEarth.Due to differential uptake in plants as well as marine carbonates
of13C, it is possible to use these isotopic signature in earth science.
In aqueous geochemistry, by analyzing theδ13Cvalue of surface and ground waters the source of the water can be
identified. This is due to the fact that atmospheric, carbonate,
and plant derived δ13C values all differ with respect toPee Dee Belemnite(PDB) standard.