Radionuclides and large particles in estuarine sediments

Abstract

Radionuclides, released into the north-east Irish Sea from the British Nuclear Fuels plc uranium reprocessing plant at Sellafield, Cumbria, UK and which are present in sediments of the Esk estuary, Cumbria, are initially associated with large (i.e. >0.5 mm) rather than fine grained (i.e. <63 μm) particles. I call these macro particles organoliths. They consist of an agglomerate of sediment grains held together with an organic iron rich matrix; their surfaces are coated with a patina of iron and manganese oxides with which the radionuclides are associated. Concentration factors (Kd's) for plutonium, americium, and other radionuclides, together with various stable elements in the patina are orders of magnitude greater than those found in bulk sediments. Some implications concerning the radionuclide content of organoliths are discussed in relation to geochemical process, pollution studies and the requirements of radiological protection.