AN ESTIMATION OF SEDIMENTATION-RATES ALONG THE RIBBLE ESTUARY, LANCASHIRE, UK, BASED ON RADIOCESIUM PROFILES PRESERVED IN INTERTIDAL SEDIMENTS

Radiocaesium has been measured, using a Ge gamma-ray spectrometer, to a depth of Im in the intertidal sediment at four sites along the Ribbl e Estuary, Lancashire, UK. Using depth profiles of Cs-137, Cs-134, and the Cs-137/Cs-134 ratio together with the published release rates fro m Sellafield nuclear fuel reprocessing plant, net sedimentation rates have been derived for the four sites. Sedimentation rates of 100- 120 mm/y were measured for Lytham Main Channel, 15-20 mm/y in the uppermos t and 30-40 mm/y in subsequent layers at Nazemount, 40-65 mm/y at Old Grange Farm and 45-55 mm/y at Preston Docks (South Bank). A peak in Cs -134 activity observed at a depth between 500-600 mm at Lytham Main Ch annel was attributed to the Chernobyl incident.