Work within the Coordinated Programme on the Cycling of Tritium and Other Radionuclides in Different Types of Ecosystems. Final Report for the Period 1 December 1972-31 May 1978

摘要

A review is attempted of uptake, retention and release patterns of plants of different trophic levels exposed to tritiated atmosphere in three different ways: stem injection, soil application and foliar absorption. Three component release patterns for tissue free water tritium (TFWT) are observed in many of the terrestrial vegetations. The mean residence time for the first major component is found to be within 1-12 days for all the terrestrial vegetations. The second and the third components form only a small fraction of the total tritium uptake and show significantly different mean residence times. An isotopic discrimination of about 30-40% against the incorporation of tissue bound tritium (TBT) is found in some algal and aquatic species and this is enhanced to as high as 90-99% for the terrestrial vegetations. Under conditions of constant specific activity, high specific activity ratios are obtained even for the few terrestrial vegetations cited. A synoptic view of the distribution data in different biochemical fractions indicate significant relative specific activity ratios in nucleic acids, protein and fats. Mathematical resolution procedures to determine the mean residence times for TFWT/TBT fractions either from separated or composite sample fractions have been reviewed. (Atomindex citation 11:541152)