Application of radionuclide ²¹⁰Pb 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.