J. Emiron. Radioucrivi!y 26 (1995) 205 2 I6 1 1995 Elsevier Science Limited Printed in Ireland. All rights reserved ELSEVIER 0265-93lX.‘95,‘$9.50 0265-931X(94)00033-6 Vertical Distribution of Radiocaesium, Plutonium and Americium in the Catalan Sea (Northwestern Mediterranean) J. Molero,” J. A. Sanchez-Cabeza,” J. Merino,’ LL. Pujol,” P. I. Mitchellb & A. Vidal-Quadras” “Grup de Fisica de les Radiations, Departament de Fisica, Facultat de Cikcies. Universitat Aut6noma de Barcelona, 08 193 Bellaterra, Spain ‘Laboratory of Radiation Physics, University College, Dublin, Ireland (Received 27 September 1993; accepted 9 July 1994) ABSTRACT Caesium-137, 239, 240Pu and 24’Am concentration profiles (O-l 000 m) have been determined in unfiltered large volume water samples collected from the Catalan Sea (northwestern Mediterranean). Results showed that radiocaesium concentration decreases quickly through the water column while the transuranic concentration increases with depth, showing a faster migration to the bottom layers. Comparing our results with those reported by% other authors (1975-1980), radiocaesium input,from Chernobyl releases has been ident$ed through the profile. In addition, transuranic concentra- tions have decreased considerably in the different layers of the profile. Integrated activities through the water column were 2.6 & 0.2 kBq m-2 ,for ‘j7Cs, 23 * 3 Bq rnp2 ,for 239~240Pu and 1.5 & 0.5 Bqm-2 .for 24’Am. According to the estimated inventory and the integrated ,fall-out in the Mediterranean area, about 56% of ‘37Cs, 27% of 23y,240Pu and 4% of 24’Am which was deposited over the Mediterranean Sea by generalized,fall- out remains at present in the ,first 1000 m of the w,ater column. Vertical distribution of 239, 240Pu/137Cs and 24’Am/‘37Cs activity ratios showed a clear separation between transuranics and radiocaesium through the water projl’le. 241Am123Y, 240 Pu activity ratio revealed,jaster sinking of americium relative to plutonium. 205