10.1021/es400896t.s001 Bruno Fiévet Bruno Fiévet Julien Pommier Julien Pommier Claire Voiseux Claire Voiseux Pascal Bailly du Bois Pascal Bailly du Bois Philippe Laguionie Philippe Laguionie Catherine Cossonnet Catherine Cossonnet Luc Solier Luc Solier Transfer of Tritium Released into the Marine Environment by French Nuclear Facilities Bordering the English Channel American Chemical Society 2013 biota HTO seawater HTO English Channel French Nuclear Facilities Bordering OBT tritium transfers English ChannelControlled amounts 2013-06-18 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Transfer_of_Tritium_Released_into_the_Marine_Environment_by_French_Nuclear_Facilities_Bordering_the_English_Channel/2404588 Controlled amounts of liquid tritium are discharged as tritiated water (HTO) by the nuclear industry into the English Channel. Because the isotopic discrimination between 3H and H is small, organically bound tritium (OBT) and HTO should show the same T/H ratio under steady-state conditions. We report data collected from the environment in the English Channel. Tritium concentrations measured in seawater HTO, as well as in biota HTO and OBT, confirm that tritium transfers from HTO to OBT result in conservation of the T/H ratio (ca. 1 × 10<sup>–16</sup>). The kinetics of the turnover of tritium between seawater HTO, biota HTO, and OBT was investigated. HTO in two algae and a mollusk is shown to exchange rapidly with seawater HTO. However, the overall tritium turnover between HTO and the whole-organism OBT is a slow process with a tritium biological half-life on the order of months. Nonsteady-state conditions exist where there are sharp changes in seawater HTO. As a consequence, for kinetic reasons, the T/H ratio in OBT may deviate transiently from that observed in HTO of samples from the marine ecosystem. Dynamic modeling is thus more realistic for predicting tritium transfers to biota OBT under nonsteady-state conditions.