摘要： 运用γ谱仪,对采自福建省兴化湾外近海海域的D37和FJ3-12孔进行了 ²¹⁰Pb 、²²⁶Ra和 ¹³⁷Cs 活度的测试,得到这3种核素活度随深度变化特征。分别运用 ²¹⁰Pb 法的CFCS模式(恒定通量恒定沉积模式,Constant Flux and Constant Sedimentation)和CRS模式(恒定供给速率模式,Constant Rate of Supply)以及 ¹³⁷Cs 时标法计算平均沉积速率,发现3种方式的计算结果存在一定差异。在排除粒度变化对核素剖面的影响后,对比不同取样深度的结果发现,指数衰减剖面不完整度(取样深度未达 ²¹⁰Pb 的本底值区)对运用CFCS和CRS模式计算平均沉积速率均有不利影响,其中对CRS模式的影响随剖面不完整性愈强而愈显著。为此提出了相关校正方法作为参考,即先根据CFCS模式估算平均沉积速率和相应的²¹⁰Pb_ex累积量,再通过CRS法建立钻孔年龄框架,由此可计算得出D37和FJ3-12孔的平均沉积速率分别为2.76cm/yr和4.53cm/yr。

关键词: 兴化湾, 沉积速率, ²¹⁰Pb, ¹³⁷Cs, 校正方法

Abstract: Core D37 and FJ3-12,collected from the offshore area of the Xinhua Bay,Fujian Province,were analyzed by γ-spectrometer to test the activities of ²¹⁰Pb,²²⁶Ra and ¹³⁷Cs and the activity characters of three nuclide with depth were abtained. It was demonstrated that there existed some differences in mean sedimentation rates of Core D37 and FJ3-12 through CFCS and CRS models for ²¹⁰Pb inventories and the ¹³⁷Cs time-scale method, respectively. After eliminating the effect of grain size changes on the nuclide profile,the difference between varied sampling depth is obvious. It is also suggested that the incompleteness of logarithmic attenuation profile(i.e., the sampling depth less than that bearing ²¹⁰Pb background value)has an adverse effect on calculating sedimentation rates by CFCS and CRS models,even more on CRS model by less incompleteness of the profile. Therefore,a rectification method was proposed to calculate the mean sedimentation rates for the upper boundary of sustaining ²¹⁰Pb(or none ²¹⁰Pb_ex)layer by the CFCS model,and then sedimentary chronology of the study cores by the CRS model with this deduced data. And the mean sedimentation rates of D37 and FJ3-12 are 2.76cm/yr and 4.35 cm/yr,respectively.

Key words: Xinghua Bay, sedimentation rate, ²¹⁰Pb, ¹³⁷Cs, calibration method

中图分类号: 

• P512.2