EXPERIMENTAL STUDIES ON THE BIOGEOCHEMICAL BEHAVIOUR OF TECHNETIUM IN THE MARINE ENVIRONMENT
Investigations have been performed under controlled conditions at realistic mass concentrations of technetium by use of the gamma emitter Tc-95m. Chromatographic and coprecipitation methods were applied to the separation of different chemical forms of technetium in sea water. In agreement with thermodynamic considerations, the anion pertechnetate was found to be the chemical form most stable in well oxygenated sea water and in aerobic sediments. In the presence of anoxic sediments, pertechnetate may be reduced and immobilized as highly insoluble compounds. Although redox conditions are responsible for the fixation of technetium, diffusion of pertechnetate through the sediment should represent the rate limiting factor. Accumulation and release kinetics were also determined in several species of marine organisms. In general, marine biota do not accumulate technetium to any remarkable extent; however, concentration factors in the range 100-1500 have been observed in some species of macrophytic brown algae, polychaetes, and crustaceans. Release of technetium, accumulated either from water or from food, by shrimp and fish occurs at a relatively fast rate. Differences in excretion kinetics exist depending upon the oxidation state of technetium initially taken up. Since it takes a long time to achieve steady state conditions, mathematical models have been successfully applied to reduce the duration of experiments designed to obtain concentration factors at equilibrium.
Bibliographic Reference: 6TH IRPA INTERNATIONAL CONGRESS "RADIATION - RISK PROTECTION", BERLIN WEST (GERMANY), MAY 7-12, 1984 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 31344 ORA
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Record Number: 1989122069900 / Last updated on: 1987-01-01
Available languages: en