Behavior of Heavy Metals and Particulate Matters in Seawater Expected from that of Radioactive Nuclides

概要

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Vertical profiles of 210Pb and 230Th in the deep water were analyzed by using a simple one-dimensional model. Both nuclides are considered to settle down with the velocity of 1×10-4 cm/sec. The diameter of particle corresponding to the velocity is calculated to be 5μ, while only about 10 % of the nuclides can be collected on filter paper with a pore size of 0.5μ. It is supposed that the nuclides exist in particulate materials which is changeable in size. This suggestion is supported from the following evidences.(1) The directly observed behavior of marine snow and the size distribution of particles observed with a coulter counter.(2) The existence of many chemical elements of which residence time is about 150 years.(3) Their possible existence as eutectic solid phases in the seawater.(4) The consistency of the observed accumulation rate of pelagic sediments with that estimated from the settling velocity.(5) The consistency of the decomposition rate of organic matter in the deep water estimated from the oxygen comsumption with that from the settling velocity.
日本海洋学会の論文