Seabed disposal program: geochemical and sedimentological assessment of deep-sea sediments. Progess report for period, 1 January--31 December 1977

Sorption experiments involving deep-sea sediments (including MPG clays) and Eu in 0.7M NaCl solutions have shown surprisingly uniform partition coefficients (Kp) of 10,000 to 70,000 for most samples at 150C. The concentration dependence of Kp is given by: Kp = bC/sup a/, where b depends on sediment type and temperature, C is the final solution concentration, and a, which is a constant for a given cation and sediment, ranges from about -0.6 to -1.0 for Eu. The Eu-sediment experiments yield similar results in both the sorption and desorption directions. The high values of ''a'' imply that sorption is very strong and approaches irreversibility at very low concentrations. The combined SLA and URI sorption results show that heavy elements, particularly rare earths and actinides, have similar Kp values at 1μM (1000 < Kp < 100,000) and similar a values of < -0.6. Magnetic and geochemical data for MPG-I sediments show consistent core to core depositional patterns like those previously reported for the MPG-II area. The magnetic data support the ichthyolith time scale and suggest that sedimentation has not suffered major interruptions for the past 70 million years. The geochemical data show trends that parallel the sorption results, supporting the hope that we will be able to predict the sorptive behavior of sediments from more easily determined geochemical properties