RADIOISOTOPES OF 13 ELEMENTS IN INTERTIDAL COASTAL AND ESTUARINE SEDIMENTS IN THE IRISH SEA

A survey has been carried out of K-40, Co-60, Tc-99, Ru-106, Sb-125, I-129, Cs-134, Cs-137, Eu-154, Ra-226, Ra-228, Np-237, Pu-238, Pu-239, Pu-240, Pu-241, Am-241, Cm-242, and Cm-243, Cm-244 activities in sediments from the Irish Sea. Several of these radionuclides were measured independently at two separate laboratories to enable the intercomparison of the results produced. The comprehensive data set generated allows the present spatial distributions of these radionuclides in coastal sediments to be examined in relation to sediment textural characteristics and, by comparison with earlier surveys, enables the temporal trends in their activities to be determined. In general all artificial radionuclides showed lower activities in sediments in response to failing discharges from Sellafield and relationships with either grain size, distance from Sellafield or both. Isotope ratios were similar to cumulative weighted activity ratios rather than present day values due to sediment mixing. Pu levels supplied evidence for the lag in response of sediment deposits with increasing distance from Sellafield due to sediment transport.