冲绳海槽沉积物混合作用的研究

MIXING RATE OF SEDIMENT IN THE Okinawa Trough

介绍了利用放射性同位素２１０Ｐｂ活度在岩芯中的垂直分布，根据沉积 作用的数学模式［５，６］，结合有关资料对冲绳海槽海水－海底界面沉积物的混合 作用强度进行了探讨。２１０Ｐｂ资料表明冲绳海槽表层沉积物中，２１０Ｐｂ放射性活 度存在空间差异，介于 ２６．２６～９２．４０ｄｐｍ／ｇ，沉积物混合系数介于 ０．５１～６． ８８ｃｍ２·ａ，这反映了研究海区不同的混合作用强度和沉积环境。

Pb activities have been determined on four Cores from the Okinawa Trough. within study area. 210Pb activities at the surface of the sediment ranged from 26. 26 to 92. 40 dpm/g. According to the Steady-state eqution, estimated mixing coefficients (Db) ranged from 0. 5 1 to 6. 88cm2. a at the four station. Excess 210Pb profile show that sediments at the sediment-water interface are mixed downward to the depth of 6- 13cm. It seems to be true that the radionuclide profiles are dominated by both biological and hydrodynamic processes which passes northward Warm Current from Pacific Water Masses. 210Pb date indicated that in the central part of the Okinawa Trough mixed intensity of sedi -ments is higher than the southern and northern part of the Okinawa Trough. It is generally accepted that observed mixing rates are higher than the central pacific Seamounts (0. 6-3cm2. a ) and estimated the distribrtion of 210 Pb activities are associated with the pacific water masses.