应用~(210)Pb的南海黑角珊瑚定年

通过高分辨低本底的α能谱检测技术对采自南海西沙群岛(JYI-1、JYI-2)和鹿回头半岛(LHT)三株黑角珊瑚骨骼中的210Pb进行了测定,利用过剩210Pb比活度在珊瑚横截面的径向分布规律,对黑角珊瑚进行年代学研究。结果表明,210Pb在珊瑚骨骼中的比活度随径向呈指数衰减,各样品中210 Pb的比活度范围分别为10.28~73.41mBq/g(JYI-1),1.50~4.72mBq/g(JYI-2)和5.35~12.67mBq/g(LHT)。这些黑角珊瑚物种都表现出了生长缓慢、生长周期长的特性。它们持续生长了约185~267a,年生长率介于17.8~26.5μm/a。而且,年生长率在不同种属、不同区域的样品间有明显区别,生长速率的顺序为:西沙(JYI-2)西沙(JYI-1)鹿回头(LHT)。放射性核素210Pb对南海黑角珊瑚定年结果与生长环计数的定年结果基本一致。这种黑角珊瑚定年方法可以为其在百年尺度上研究气候环境的演变和重建提供基础数据。

Application of Radionuclide 210 Pb in Dating of Black Coral

In this study, the α spectrometry technology was used to estimate the activities of ²¹⁰Pb in the skeletons of black corals collected from the Xisha Islands (JYI-1, JYI-2) and Luhuitou Peninsula (LHT) of the South China Sea. According to the radial distribution characteristics of excess ²¹⁰Pb in the cross-sections of black corals, we studied the chronology of black corals. The results reveal that specific activity of ²¹⁰Pb exhibits an exponential decrease with distance from the edge of the black corals. The ranges of ²¹⁰Pb specific activity in the coral skeleton are 10.28-73.41 mBq/g, 1.50-4.72 mBq/g and 5.35-12.67 mBq/g in the JYI-1, JYI-2 and LHT respectively. All black corals are long-lived and slow-growing organisms. They have been growing continuously for 185-267 a, with growth rates ranging from 17.8 to 26.5 μm/a. Moreover, the annual growth rates exhibit obvious distinction in diverse species collected from different regions. The sequence of the growth rate is JYI-2>JYI-1>LHT. With respect to counting growing rings, the results of radionuclide ²¹⁰Pb in dating of black corals reveal a good conformity. The dating of black corals in this study will provide the basic data to study the evolution and reconstruction of climate change in the past centuries.