size of these particles places them in a size distribution obviously smaller shan those reported by Anikouchine (op. cit.), and more nearly like that repoted by Glasstone (op. cit.). 5.3 Bistribution of Radionuclides with Depth in Sediment Ccres Measurements of the concentration distribution of elements in the sedimentary column are fundamental to the study of sedimentology and the exchange of materials across the sediment-water interface. In Bikini Jagoon, measurements of the radionuclide distributions with depth were considered to be particularly informative, since debris from several detonations have been added to the lagoon at different times. Nine sediment cores were collected from various locations in the Tagoon (Table 4). The radionuclide concentrations measured in the core collections 2re shown in Appendix III and in Tahles 15 and 16. Three types of profiles of the radionuclide concentration with depth were ohserved. These occurred in: (1) Crater sediments (Stations C-3 and C-12) which had either relatively homogenous and/or constant distributions of most radionuclides with depth; (2) Northwest quadrant lagoon sediments (stations B-2, R-20 and R-21) which had large proportions of finely pulverized material and whose radionuclide concentrations changed regularly with depth; and (3) central and eastern lagoon sediments (stations B-15, B-16, B-27 and 8-30) which had variable radionuclide concentrations with depth. 5.3-1 Crater station profiles The distribution of radionuclides measured in the sediment core collected from the center of Zuni Crater (station C-12) are shown in Tables 15, 16 and Table 4 in Appendix III. No appreciable portion of the Sediments in the Zuni Crater core were finely pulverized. The distribution of all radionuclides measured in this core were nearly constant with depth,