Appendix Q: site survey and assessment and multibarrier identification and quantification, 1979

Studies of the geochemistry of sediment cores from North Pacific study areas MPG-I and II show excellent correlations of variations in the influx of detrital, biogenic, hydrothermal, and hydrogenous material spanning the past 65 million years. This evidence of very long-term lateral coherence over a distance of more than 720 km confirms our earlier conclusions as to the uniformity and predictability of deposition in the mid-ocean pelagic clay environment. Sorption experiments show that pH changes from 1.4 to 8 produce about a 6-fold change in Kp for Eu; comparable to the change due to an order of magnitude change in dissolved Eu concentration. Also, isotopic exchange of Eu is rapid on pelagic sediments. Finally, Eu at low concentrations has Kp values in seawater comparable to those in 0.7M NaCl. Work on ion migration in undisturbed deep-sea sediments shows Kd values for Ra-226 of 103 to 104 in sediments, but up to 107 in manganese nodules. Kd values for Th-230 and Pa-231 in manganese nodules are roughly 109 the consistency of batch and column sorption data and observations of diffusion in nature confirm the effectiveness of deep-sea red clay as a barrier to cation migration