用γ谱方法测定大鹏湾的沉积速率

用低本底γ谱系统测量沉积物柱芯分层样品的~（２１０）Ｐｂ和~（１３７）Ｃｓ含量，及最小二乘拟合方法得到沉积曲线，从而求出大鹏湾内外４个采样站位沉积物的沉积速率：~（２１０）Ｐｂ方法为０．４６～０．２７ｃｍ·ａ~（－１）；~（１３７）Ｃｓ方法为０．３８～０．１０ｃｍ·ａ~（－１），其值随远离海岸方向而减少。在该海区~（１３７）Ｃｓ方法因外部扰动因素较多，不如~（２１０）Ｐｂ方法准确、可靠。

Determination of Sedimentation Rates in the Mirs Bay Sea Areas with Gamma Spectrometry

Cylindrical samples of sediments are obtained from 4 sea areas next to the Mirs Bay to the South China Sea. An N-type high purity germaium low background gamma spectrometry system has becn employed to measure the Pb-210 and the Cs-137 contents in the layered sam- plees.The sedimentation curves of Pb-210 and Cs-137 are acquired using the least squares fit method.The sedimentation rata at the four sampling sites are evaluated.our results show that the sedimentation rate decreases when the sampling sites are farther away from the Mirs Bay into the South China Sea,In particular,the rate calculated using the Pb-210 activities decreases from 0.46 to 0.27 cm/a,and that using the Cs-137 method from 0.38 to 0.10 cm/a,The Cs-137 method vields resuIts which are subiected to external disturbance to a greater extent,and is thus less reliable than the Pb-210 method.