THE UPTAKE OF TRITIUM ONTO SEDIMENTS IN AQUATIC SYSTEMS

The refuelling and refitting of submarines in the Tamar Estuary causes the disposal of low-level liquid waste into the lower estuary. This contains up to 800 gigabecquerels (G8q) of tritium per year plus an additional aerial discharge of gaseous tritium is released. The actual level of tritiated water disposed per refuelling is in itself not documented. The aim of this project was twofold firstly to quantify the concentration of tritium in the sediments through analysis of pore water, the electrostatically bound fraction and the sediment bound fraction. This was to assess the levels already available. The second stage was to quantify the potential uptake available within the system if tritium disposal continues. Overall there is a large discrepancy between sites assessed in the Tamar. This can be justified by the geographic location and water flow at sites but does indicate a difference in an order of magnitude from sites just 0.2 Km apart. The volumes in the sediment are ten times greater than that either electrostatically bound or in the pore water. The dosing experiments gave low K! for tritium using coarse bed sediments however there was significantly measurable uptake, and the maximal volume capable of being taken up onto sediments has not been reached, within the current environmental levels. The future for the study of the uptake should be to quantify the maximal uptake possible per unit volume and to quantify the volume to be re-released based on a gradient of tritium for understanding of future bed sediment source for the estuary.Faculty of Scienc