Pu, Sr,Cs and Co contents of deep-sea sediments in the Western North Pacific.

Abstract

239,240Pu,90Sr,137Cs and 60Co concentrations in the surface layer (0-2 cm) of the deep sea sediments, which were collected along 147°E from 29° N to 40°N during 1985 to 1987, were radio-chemically determined. The range of the concentrations of the four artificial radionuclides varies by more than ten times. These latitudinal distributions have a peak in 36° N 38° N, where the ocean currents Oyashio and Kuroshio contact, and decrease both directions to the north and south. The contents per unit area increase from 29° N to 37° N and vary by about ten times. These profiles with latitude are related to those of the mathematical product of the concentrations in the surface sea layer and the biological productivity of the sea. Each of the coefficients of correlation between these nuclides is as good as more than 0.9. The ratios of 239/240Pu/137Cs, 90Sr/137Cs and 60Cn/137Cs are nearly constant and have no remarkable profile with latitude. The ratios of 239/240Pu/137Cs and 60Cn/137Cs in the marine sediments are much the same as those of the product of the contents m the water column and the concentration factor of the marine living materials, whilst that of 90Sr/137Cs is half. These results suggests that most of 239,240Pu,90Sr,137Cs and 60Co existed in the deep-sea sediments first dissolved in the surface sea layer, and then sank with the sinking particles produced by the living materials, and reached to the sea bed.