17 that the anionic species is the carbonato-complex of plutonium. A comprehensive study of the elemental physical states of nuclear weapon debris in seawater was reported by Frefling and Ballou (op. cit.) from in situ and Jaboratory simulation experiments, using radioactive particles. They found that the majority of the rare earth radionuclides measured were associated with the particulate fraction of water samples and the remainder was associated with the colloidal fraction. Although no plutonium or americium data were presented, evidence for the simultaneous coexistence of several oxidatfon and phystcal-chemical states for neptunium was found. Sugihara and Bowen (1962) and Bowen and Sugihara (1963) found that the rare earth radionuclides 144 ne and V7 on in fallout over the ocean, rapidly become associated with sinking particulate matter after they enter seawater and are consequently fractionated from soluble faliout radionuclides (such as ory, While there exists an uncertainty as to the degree which individual fallout radionuclides are isotopically inert or equilibrated with their seawater counterparts after fallout, a rare earth-plutonium analogy is suggested in that similar mechanisms (Noshkin and Bowen, 1972) can explain the depletion of plutonium from oceanic surface waters. In regard to the geochemical “{rertness" of fallout radionuclides in seawater, Volchok et al. (1971) have G¥scussed the relevant literature, and it appears that no definitive conclustons can be drawn, It is also of some interest to note Sugihara and Bowen's sucrestion that the fractionation of promethium (from cerium), via the apparer’ association of promethium with faster settling particles, is due to the “\"ference in oxidation states of Ce (+4) and Pm (+3) in the ocean. Several recent studies (Polzer, 1971; Silver, 1971; and Andelman and Polrell, con, cit.) have been directed toward the distribution of soluble