Tritium Oxide Uptake and Desorption Kinetics in a Primary Producer: Chlorella Pyrenoidosa

摘要

The alga Chlorella pyrenoidosa grown in batch culture under chronic tritium oxide exposure was used to model behavior of tritium at the primary producer level of an aquatic food chain. The specific activity ratio of organically bound tritium to medium tritium increased during initial growth stages, then reached an asymptotic steady state value of 0.59 after approximately seven cell doublings. The intracellular to extracellular concentrations of tritium oxide appeared to be in equilibrium. Loss of previously formed organically bound tritium in cells transferred to tritium-free media averaged less than 5 % for exponential growth phase cultures which had undergone more than three cell doublings. Over a comparable time period, a greater loss of organically bound tritium from stationary cells (average 13.4 %) was attributed to increased degradative metabolism in senescent cultures. Concentration of tritium in organically bound form may exceed environmental tritium oxide levels under dynamic conditions in which a pulse of tritium oxide to the environment is dissipated over time.