Radioactivity Dynamics in River System
（2015）
ＱHow does radioactive cesium carried down by rivers move in the sea? 【Example of analysis】
ＡSimulations indicate that river water flowing into estuaries spreads over the sea surface.
This is presumably because river water is less saline and warmer than seawater and thus lower in density.
On the other hand, we have found that there are seabed flows in the opposite direction, or toward the estuary, moving river-derived soil and other materials carried away from the coast back in the onshore direction.
Fig.1 Estimated Cs-137 deposition at the time of the September 2015 typhoon, based on simulation
- The movement of river water flowing into the sea was analyzed by 3D simulation (3D-Sea-SPEC).
- River water flowing into estuaries spreads over the sea surface due to salinity difference between river water and seawater.
- On the seabed, as opposed to the sea surface, flows are generated in the direction of the estuary, presumably moving river-derived soil and other materials back toward the coast.
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