【摘要】 <正> U,Ra,Th和⁴⁰K是广泛分布于自然界中的天然放射性元素,研究其形态、含量、分布和转移规律是地球化学的重要内容。海洋沉积物是一个非常复杂的体系,除自身包括许多同位素以外,还可以从海水中吸附和交换一些同位素。海洋沉积物中的同位素含量很更多还原

【Abstract】 The determinations and geochemieal studies of U, Th, Ea, K (40K) in sediments of Okinawa Trough were carried out with 8180-4K multichannel Ge (Li) y spectrometer in 1981. The region of the investigation is located in the 124-129°E and 26-31°N. The mean concentrations of U, Th, Ea, K (40K) are 2.18 ppm, 8.76 ppm, 9.58 ×10-13 g/g and 1.85×10~2 g/g (or 15.53 pCi/g) respectively. The concentrations and ratio of uranium and thorium in sediments of Okinawa Trough are similar to those in the sediments of Huanghai Sea (Yellow Sea), Bohai Bay, the continental shelf in the Bast China Sea, as well as the terrestrial materials in China. This shows that there are close relalionships between the Okinawa Trough and shelf of the Bast China Sea.The distributions of U, Th, Ea, K (40K) are related to their physical-chemical property, redox state, biotic activation and the deposition of the biotic debris and grain size of the sediments in the Okinawa Trough.The distribution of Uranium is remarkably affected by redox state in this region. The changing of its valence from six to four and deposition from seawater to sediment would be taken place in above environment.The contents of Th, K, Ea increased gradually from the outer to inner region of the Okinawa Trough with the increase of clay component and the decrease of grain size.更多还原