放射性セシウムの河川を介した陸域からの海洋環境への影響について

摘要

In order to evaluate the importance of desorbed ~(137)Cs from riverine suspended particles on the dissolved ~(137)Cs flux from rivers to the marine environment, the samples were collected from stations along the Abukuma (5 December 2013), Kuji (20 November 2013), Naka (20 November 2013),and Tone (29 October 2013) rivers. We estimated the extent of the desorbed fraction from riverine particles by conducting a particle-seawater partitioning and desorption experiment in which sieved particles (<74 μm) from the riverbank soils and river-bottom sediments were added to filtered (<0.45 μm) seawater. We calculated the flux of '~(37)Cs via the rivers (i.e., the dissolved phase in river water plus the desorbable Cs fraction in riverine suspended particles) from the riverine water discharge of dissolved ~(137)Cs activity in the river water, and the experimentally estimated desorbed 137Cs fraction (0.75-6.6%) from particulate ~(137)Cs in the river water. The estimated ~(137)Cs fluxes are significantly larger than the fluxes calculated without the desorbed fraction. Thus, it is necessary to take into account the flux of the desorbable ~(137)Cs fraction in riverine suspended particles.