The oceans are the basins into which are poured all the nutrients or
wastes transported from the land by rivers and winds.
The difficulty of determining the fate of radionuclides in aquatic
systems is complicated by chemical and biological differences within the
system and by the variety and scope of the circulatory mechanisms. In
oceans the sheer immensity of the water volume usually makes observation
superficial or fragmentary. Rivers present great differences in flow,
and lakes vary in internal dynamics. Above all, an ocean, a river, or a
lake is an area of constant physical and biological motion and change.
In the ocean the surface waters form a theater of kaleidoscopic, and
frequently violent, action. The presence of man-made radioactivity in
water has made it possible to follow the disposition of nutrients and
wastes in the restless aquatic ecosystem.