Étude des transferts du tritium atmosphérique chez la laitue: étude cinétique, état d'équilibre et intégration du tritium sous forme organique lors d'une exposition atmosphérique continue

Abstract : This thesis has explored the mechanisms of tritium absorption and incorporation in a human-consumed plant, lettuce (Lactuca sativa L.), due to atmospheric exposure. Foliar uptake appears to play a key role in absorption of tritium as tissue free water tritium. Whatever the development stage and the light conditions, the specific activity in tissue free water reaches that of water vapour in air in several hours. The specific activity ratio is then about 0.4. The time to reach equilibrium in soil is over 24 hours in most cases: the specific activity ratio ranges then 0.01 to 0.26. Incorporation rate of tissue free water tritium as organically-bound tritium has been estimated to 0.13 to 0.16 % h-1 in average over the growing period of the plant, but marked variations are observed during growth. In particular, a significant increase appeared at the exponential growth stage. Deposition and diffusion of tritium in soil lead to significant OBT activities in soil. Results globally indicate equilibrium between the different environmental compartments (air, soil, plant). However, some experiments have revealed high OBT concentrations regarding atmospheric level exposure and ask for a possible phenomenon of local tritium accumulation in OBT for particular conditions of exposure.
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Cécile Boyer. Étude des transferts du tritium atmosphérique chez la laitue: étude cinétique, état d'équilibre et intégration du tritium sous forme organique lors d'une exposition atmosphérique continue. Physique [physics]. Université de Franche-Comté, 2009. Français. ⟨tel-00464333⟩

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