EFFECT OF NO3- ON THE FATE OF (TCO4-)-TC-99 SYSTEM IN THE SOIL-PLANT SYSTEM

This work was undertaken to study the effect of NO3- fertilization on the uptake of (TcO4-)-Tc-99 by plants. Rye-grass (Lolium perenne) was grown in a growth chamber on a silty loam soil to which were added inc reasing quantities of ammonium nitrate (21, 50 and 100 mg N kg(-1)). S oil samples were then amended with (TcO4-)-Tc-99 at a constant level o f 29.6 kBqkg(-1) dry weight. Total initial NO3- content was 43.3, 57.8 and 82.8 mg N kg(-1), and total NH4+ content was 24.7, 39.2 and 64.2 mg N kg(-1). Three cuts were made at 4-week intervals, and aerial biom ass was analysed for total Tc-99 and N, Results showed that total upta ke of Tc-99 was decreased by increasing mineral N additions at the fir st cut, as mineral nitrogen was not a limiting factor for plant growth at this stage. Technetium-99 content in plants varied from 64% of the total applied Tc-99 with the lowest NO3- content to 31% with the high est. However, at the third cut, cumulative Tc-99 uptake reached the sa me level for the three treatments (80-83%) with no further effect of i nitial N applications, as NO3- was depleted in the soil. Therefore, (T cO4-)-Tc-99, was diluted in the pool of soil NO3- and was absorbed pro portionally to nitrate by rye-grass. Copyright (C) 1997 Elsevier Scien ce Ltd.