# The Impact of Tritium in the Environment
## 5 Isotopic Effects of Hydrogen in Living and Inanimate Matter  
Isotopic effects, i.e., differences in the properties of isotopes of a chemical element or its compounds containing different isotopes, are most often caused by differences in the mass of the isotope's nuclei (isotopic effects of the first kind), but they can also be caused by differences in nuclear magnetic properties (isotopic effects of the second kind). The isotopic effects of the first kind are stronger the greater the difference in isotope masses, i.e., with increasing atomic mass, the isotopic effect decreases, and the largest is observed for isotopic hydrogen compounds. The isotopic effects of the second kind are instead caused by differences in properties of nuclei such as spin, the energy of \(\gamma\)-quanta emitted after neutron capture, the presence of isomeric properties, etc. Hydrogen isotope fractionation in inanimate matter has been studied in some detail. It is known for certain that in living matter, isotope effects are associated with photosynthesis processes, which manifest mass-dependent (primarily diffusion and kinetic) effects of isotope fractionation. For H-D and D-T pairs, both mass-dependent and nuclear spin (magnetic) isotopic effects can coexist simultaneously, and their magnitudes can even be comparable. For the H-T pair, the nuclear spin effect is insignificant, since the spins of hydrogen and tritium are the same. However, the masses of tritium and protium differ by a factor of three (300%), which causes significant mass-dependent isotopic effects in gas molecules and isotopic compounds. Thus, in living and inanimate matter, the most significant mass-dependent effects in the isotopic fractionation of protium and tritium are for protium/deuterium and, likely, tritium/deuterium, and along with mass-dependent effects, the nuclear spin (magnetic) effect plays a significant role. The increase in the binding energy in isotopic hydrogen compounds from protium to tritium largely explains several isotopic effects. In an isotopic water molecule (HTO), the T-O covalent bond is stronger than the H-O bond, so it is expected that protium is more attracted to the proton form (hydroxonium H\({}_{3}\)O\({}^{+}\)), and tritium is mainly attracted to the hydroxyl (TO\({}^{-}\)) groups. This substantiates the possibility of isotopic separation of hydrogen by electrodialysis methods, as well as by isotopic substitution in structural OH-groups of clay minerals (see Section 3). Significantly stronger bonds of the superheavy hydrogen isotope in the structure of organic molecules may also explain the effects of tritium enrichment in the organic matter of living organisms observed by many authors. During biological evolution, a mechanism of preferential assimilation of the light isotope was created, which has been confirmed by numerous studies of H/D and \({}^{12}\)C/\({}^{13}\)C in living organisms. Therefore, there are reasonable grounds to believe that the same pattern is observed for the H/T ratio. However, due to stronger bonds with carbon and oxygen, tritium is removed from an organic molecule much more slowly than protium. At the same time, in its aqueous form, the concentrations equalize several orders of magnitude faster. Therefore, after the assimilation and formation of organically bound tritium (primarily because of photosynthesis), tritium is excreted from intracellular water into the external environment (atmospheric moisture, soil solution, water body) much faster than from the organically bound form. In this regard, the content of organically bound tritium may exceed its concentration in the water of a dynamic environment for a certain period. This is especially true for studies in accident zones accompanied by short-term releases of tritiated water, routine releases of NPPs, and radioactive waste storage facilities that are metastable with respect to releases of the aqueous form of tritium.