Environmental actinide research. Present and future situations on Pu research

With looking back on the environmental radioactivity researches, paper of environmental Pu is stated since 1996. On atmosphere environment, 137Cs, 90Sr and 239,240Pu, which do not exist in nature, are used as tracers of atmosphere to make clear global material circulation in atmosphere. By observation of fallout of 239,240Pu, there were rare amount of fallout from the nuclear tests in atmosphere, but re-flotation from fallout was observed. A state and measurement of each particle size of aerosol are reported. On land environment, there are hot-particle of environmental Pu in local area of nuclear test, nuclear accidents of nuclear installations and reprocessing plants. They changed with time. The states of hot-particle are observed by SEM, ED-XRF, XRD, laser and synchrotron orbital radiation. Pu behavior in land was reported. Effects of bacteria and Lichens on Pu and Pu in ground water and river were studied. On hydrosphere, the transfer and distribution model of Pu and a simulation model of the physical and chemical state of Pu in the Irish Sea were constructed by many kinds of researches. Local pollution of the coast of Spain, Greenland and the Marshall Islands are reported. The depth distribution of 239,240Pu in the sea was clear. The sedimentation behavior of Pu in the sea is studied. Today, the very low concentration of Pu in the sea is measured by ICP-MS, TIMS and AMS. (S.Y.)