Surface distributions of artificial radioactivities in the Eastern North Pacific and Indian Ocean.

Abstract

The concentrations of artificial radionuclides, that is, 90Sr, 137Cs, 144Ce, and 106Ru, in the surface sea waters in the Eastern North Pacific in 1980, and in the Indian Ocean during 1979 to 1981 were measured by radiochemical analysis. The concentrations of these radionuclides in the surface sea waters in the Eastern North Pacific are about the same as those in the Western North Pacific, while the concentrations in the Indian Ocean are about half of them. Concentrations of 106Ru and 144Ce are generally low over both oceans, and no significant tendency is found in their latitudinal distributions. On the other hand, the concentrations of 90Sr and 137Cs show similar latitudinal changes. Namely, in the Eastern North Pacific, they have a maximum in the latitudes of 30 °－33 °N, and decrease in both directions to the north and south. While in the Indian Ocean they have a maximum in the latitude of about 20°S, they decrease abruptly from 35°S to 45°S and are extremely low levels south of 45°S. The latitudinal distributions of concentrations of 90Sr and 137Cs are not in agreement with that of 90Sr deposition. This suggests the influence of the advection and diffusion of fallout in the sea.