| Research Abstract |
Sediments at the bottom of the Omura bay was analyzed. The radioactivity was analyzed by a Germanium semiconductor detector. The principal elements were analyzed by the inductively coupled, plasma atomic emission spectrometry (ICP-AES). The trace elements were mainly analyzed by the inductively coupled plasma mass spectrometry (ICP-MS).
From the radioactivity of Pb-210, horizontally separated core samples of the sediments were dated. The sedimentation rate along the coast tends to be faster than the middle of the bay. The tendency is same as Zbkyo bay and Osaka bay. The vertical distribution of Cs-137 did not show clear peak of the Global fallout of the nuclear tests and the dating with Cs-137 distribution was difficult.
The distributions of the principal elements, P, Ti, K, Mg, Na, Al, and Ca were almost uniform vertically and horizontally. The concentration of K, Ti, Y, Rb, Sr, Zr, Nb, Cs, Hf, Th, Na, Zn, W, Pb and Cd was higher than the average concentration of the earth's crust. In the elements, concentration of Na, Zn, W, Pb and Cd were increasing upward. The concentration of Cu was also clearly increasing upward. It is not appropriate to conclude easily that these trace elements pouring into the bay increase with the years because these elements may liquate out up to the surface. But concentration of Fe and Mn, which is known to liquate in anoxic condition, was decreasing upword oppositely. In the elements increasing upward, Cd is an important environmental factor, and if it is increasingly pouring into the bay, it may be the sake of human activity, and very noteworthy result.
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