Hydrogen isotope biogeochemistry
Hydrogen isotope biogeochemistry (HIBGC) is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. Hydrogen has two stable isotopes, protium 1H and deuterium 2H, which vary in relative abundance on the order of hundreds of permil.
Source: Wikipedia — Hydrogen isotope biogeochemistry (CC BY-SA 4.0)