Results of experimental research on the transfer of tritiated water to cultivated vegetables

An overview of the experiments performed since 1968 in the framework of the studies on the transfer of tritium in terrestrial food chains is presented. The experiments varied widely and modes of exposure were: a) uptake of tritium through roots from soil irrigated; b) foliar uptake of tritium from sprayed tritiated water; c) certain plant foliages were exposed to vapour (in the THO form) under controlled conditions. Mostly the activities applied were a few mCi/m2, excepted in the irrigation experiments, planned to produce forage for transfer studies to animals, in this latter case the activities applied were a few hundred mCi/m2. The study of tritium turnover in the water compartment indicates the incorporation of a definite fraction in the organic constituents; the levels of incorporation of tritium as OBT (organic bound tritium) are presented and discussed. In general, the behaviour of tritium is qualitatively similar for the various modes of exposures with the major part of tritium being associated with short TFWT residence-time and a small percentage with long residence-time (25 to 52 days) which might be attributed to organic fraction. (author)