南沙海域沉积物^(226)Ra和^(210)Pb的分布特征及环境意义  

Characteristics of distribution and environmental significance of ^(226)Ra and ^(210)Pb in sediments in Nansha sea area

作　　者：邓爽 刘劲 吴雨田 肖静水[1] 刘广山 李超 彭安国[1] DENG Shuang;LIU Jing;WU Yutian;XIAO Jingshui;LIU Guangshan;LI Chao;PENG Anguo(School of Nuclear Science and Technology,University of South China,Hengyang,421001,China;College of the Environment and Ecology,Xiamen University,Xiamen,361005,China)

机构地区：[1]南华大学核科学技术学院,衡阳421001 [2]厦门大学环境与生态学院,厦门361005

出　　处：《环境化学》2021年第8期2535-2543,共9页Environmental Chemistry

基　　金：核燃料循环技术与装备湖南省协同创新中心开放基金(2019KFZ09);湖南省教育厅项目(19A433,12c0335);湖南省大学生创新项目(S201910555097)资助.

摘　　要：用HPGeγ谱方法测定了6个来自南沙海域沉积物岩心的226Ra与210Pb,研究结果表明,226Ra的活度变化范围为(8.81±0.96)—(38.51±0.73)Bq·kg^(−1);210Pb的活度变化范围为(17.2±1.87)Bq·kg^(−1)至(143.28±3.31)Bq·kg^(−1)。226Ra和210Pb核素含量随岩心深度的增加总体上呈现不断减小的趋势,但在其中两个站位,226Ra的含量变化随着岩心深度增加先微弱增加,然后再逐渐减小。比较这6个岩心中226Ra与210Pb的活度发现,226Ra活度的变化范围相对较小,210Pb活度的变化范围相对较大,且226Ra与210Pb没有达到放射性平衡,有着明显的过剩210Pb(210Pbex)。由岩心中210Pbex的垂直分布计算了这6个岩心中的沉积速率,其变化范围为0.270—0.652 cm·a^(−1)。不同站位沉积速率的大小反映了陆源碎屑输入和生源碎屑输入对该海区沉积过程的影响。同时,在南沙海区复杂的生态系统中,底栖生物的生物扰动和水流也是影响沉积环境特征的重要因素。The results of the determination of 226Ra and 210Pb in six sediment cores from Nansha sea area by high-purity germanium(HPGe)γspectrometry were as follows:the radioactivity of 226Ra ranged from(8.81±0.96)—(38.51±0.73)Bq·kg^(−1);210Pb from(17.2±1.87)—(143.28±3.31)Bq·kg^(−1).The activities of 226Ra and 210Pb generally decreased with the depth.However,226Ra activity was observed to increase with the depth in the upper sediment layer at two stations(BKAS12 and BKAS64).Comparing the activities of 226Ra and 210Pb in these six cores,it was found that the range of 226Ra activity was relatively small and the range of 210Pb activity was relatively large.At the same time,226Ra and 210Pb did not reach radioactivity balance,so there was obvious excess 210Pb(210Pbex).According to the vertical distribution of 210Pbex,The sediment accumulation rate ranged from 0.270—0.652 cm·a^(−1) in the six cores.At different station,the magnitude of sediment accumulation rate could reflect the impact of terrestrial debris input or/and biogenic debris input during the sedimentation process.In addition,the bioturbation and water flow were also important factors affecting the characteristics of sedimentary environment in the complex ecosystem of Nansha sea area.

关 键 词：放射性核素 Γ能谱 沉积物岩心 沉积速率 

分 类 号：X55[环境科学与工程—环境工程]