南海现代珊瑚骨骼中放射性核素特征指纹

利用地表实验室高纯锗γ谱仪、中国锦屏极深地下实验室高纯锗γ谱仪、低本底β计数器系统测定我国南海1500km空间跨度上10个不同站位、5种不同种类和形状的现代珊瑚骨骼中6种最主要的天然放射性核素（²³⁸U、²²⁶Ra、²²⁸Ra、⁴⁰K）和人工放射性核素（¹³⁷Cs和⁹⁰Sr）的含量,获得现代珊瑚骨骼中放射性核素平均活度排序为²³⁸U（29.94Bq/kg） > ⁴⁰K（11.72Bq/kg） > ²²⁸Ra（6.37Bq/kg） > ²²⁶Ra（3.16Bq/kg） > ⁹⁰Sr（1.21Bq/kg） > ¹³⁷Cs（<0.06Bq/kg）.除了岸礁的珊瑚骨骼中²²⁸Ra活度高于环礁的珊瑚骨骼中²²⁸Ra活度的现象外,不同种类、不同离岸距离的珊瑚骨骼之间的同种放射性核素活度没有显著差异.本研究进一步对比珊瑚骨骼、珊瑚礁区沉积物、非珊瑚礁区的海洋沉积物、全球土壤的放射性核素活度含量,阐明珊瑚礁区是地表罕见的极低放射性水平区域,并指出现代珊瑚骨骼具有极低的²²⁶Ra/²³⁸U活度比值（~0.1）和极高的⁹⁰Sr/¹³⁷Cs活度比值（1000）的指纹特征.

Fingerprints of radionuclides in modern coral skeletons in the South China Sea

Naturally occurring radionuclides (²³⁸U, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) and artificial radionuclides (¹³⁷Cs and ⁹⁰Sr) were measured using low background β counter system and High Purity Germanium (HPGe) γ spectrometry in 5 genera of coral skeletons collected from 10 locations in the SCS with a spatial coverage of 1500km. Mean activities in modern coral skeletons decreased from ²³⁸U (29.94Bq/kg), ⁴⁰K (11.72Bq/kg), ²²⁸Ra (6.37Bq/kg), ²²⁶Ra (3.16Bq/kg), ⁹⁰Sr (1.21Bq/kg) to ¹³⁷Cs (<0.06Bq/kg). There were no significant trends of activity in relation to coral genera or distance to the land, with an exception of higher²²⁸Ra activity in the fringing reefs than in the atoll reefs. Cross-system comparisons of radioactivity in coral skeletons, sediments nearby or outside coral reefs, and global soil revealed coral reefs as extremely low radiation area on the Earth's surface. It was also found that modern coral skeletons were characterized by two common fingerprints of radionuclides (²²⁶Ra/²³⁸U and ⁹⁰Sr/¹³⁷Cs), including extremely low activity ratio of ²²⁶Ra/²³⁸U (~0.1) and extremely high activity ratio of ⁹⁰Sr/¹³⁷Cs (1000).