Zaborska Agata, Carroll Jolynn, Papucci Carlo, Pempkowiak Janusz
Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81-712 Sopot, Poland.
J Environ Radioact. 2007;93(1):38-50. doi: 10.1016/j.jenvrad.2006.11.007. Epub 2007 Jan 17.
(210)Pb geochronology is a widely used tool in sedimentological studies aimed at the absolute ages of modern sediments (up to 100 years). (210)Pb activities required to model sedimentation regimes are measured using either alpha, gamma or beta spectrometry. Sediment accumulation rates derived from (210)Pb activity profiles measured by these methods are often used interchangeably in mass balance studies. Yet there is a lack of investigations considering the comparability of data derived using different analytical methods. Differences between methods could be caused by different behaviors of (210)Pb and (210)Po (used for alpha measurement) in the marine environment. In gamma spectrometry errors may arise when many gamma emitters are measured simultaneously and their activity peaks overlap. In alpha spectrometry chemical separation of (210)Po may result in analytical error due to incomplete sample dissolution. In the present study we evaluate total, supported and excess (210)Pb activities and their use in deriving sediment accumulation rates and (210)Pb excess inventories for three sediment cores collected from the Barents Sea. (210)Pb activities derived by alpha and gamma methods are shown to agree within counting error and there is also good agreement in the derived sediment accumulation rates. The inherent compatibility of analytical results based on alpha or gamma techniques is established.
²¹⁰Pb年代学是沉积学研究中广泛使用的一种工具，用于确定现代沉积物（距今100年以内）的绝对年龄。模拟沉积过程所需的²¹⁰Pb活度可通过α能谱法、γ能谱法或β能谱法进行测量。通过这些方法测量²¹⁰Pb活度剖面得出的沉积物堆积速率，在质量平衡研究中经常被交替使用。然而，目前缺乏对不同分析方法所得数据可比性的研究。不同方法之间的差异可能是由于²¹⁰Pb和²¹⁰Po（用于α测量）在海洋环境中的行为不同所致。在γ能谱分析中，当同时测量多个γ射线发射体且其活度峰重叠时，可能会产生误差。在α能谱分析中，²¹⁰Po的化学分离可能会因样品溶解不完全而导致分析误差。在本研究中，我们评估了从巴伦支海采集的三个沉积岩芯中的总²¹⁰Pb活度、支持性²¹⁰Pb活度和过剩²¹⁰Pb活度，以及它们在推导沉积物堆积速率和²¹⁰Pb过剩存量中的应用。结果表明，通过α能谱法和γ能谱法得出的²¹⁰Pb活度在计数误差范围内一致，推导得出的沉积物堆积速率也具有良好的一致性。由此确定了基于α或γ技术的分析结果具有内在的兼容性。
