Isotope Notation of Radioactive Elements
Channel: Dominik Hezel
Date: 2023-04-12

Isotope compositions are given relative to a reference isotope composition. Such reference isotopes are often the composition of the Earth or CI chondrites. When the considered isotope is a radioactive system, the reference isotope composition is not fixed, but changes over time. The composition of a sample is then always calculated relative to the current composition of the reference. This means, the reference value is not a fixed value, but the value at a certain time. This is unproblematic for present day samples, which are also referenced to the today's composition of the reference isotope. But this change is critical to consider when modelling the evolution of a reservoir. In this case the composition of the modelled sample is always referenced to the reference isotope composition at the specific time. This isotope notation of radioactive elements is also the reason why the value of the reference is always 0.