Bioavailability of technetium from artificially labelled north-east atlantic deep-sea sediments

Laboratory experiments were designed to measure the uptake of Tc by clams from North-East Atlantic sediments which were contaminated with different oxidation states of ^95mTc. Distribution coefficients between solid sediment and pore water were similar for Tc IV and VII and never exceeded 3·5 during the 36-day experiment. Furthermore, ^95mTc was rapidly leached from the sediments with a half-time of about 4·5 days. Biological uptake was low, with transfer factors between clam tissues and sediment ranging between 0·04 and 0·6. Greater relative uptake was noted in the soft tissues than in shell, although the latter contained the largest fraction (70%) of the clam's whole body ^95mTc content. Contaminated clams, transferred to uncontaminated sediments, displayed a very long biological half-life (～120 days) for ^95mTc. This observation suggests that following acute contamination, clams living in an environment of this type would still retain Tc in their tissues long after the radionuclide had been leached from the sediments.