湖泊碳库效应及校正方法

The Reservoir Effect of Radiocarbon Dating in Lake Sediment System

湖泊作为过去环境变化的信息载体,可以很好地提供高分辨率的连续记录,因此常被用来进行定年研究。湖泊沉积物放射性碳定年由于缺乏陆源植物残体、碳屑等可靠的定年材料,多选用其他材料(如全样有机质、水生残体及各类壳体),但是这些材料通常受到"碳库效应"(The reservoir effect)的影响,而使得年代结果失真,导致难以建立高精度的年代框架,成为这一领域研究放射性碳年代应用的瓶颈。因此,如何对湖相沉积物14 C年代结果进行有效的碳库效应校正,对高精度年代序列的建立具有重要意义。本文综览了近几十年来针对湖泊碳库效应进行研究所取得的一系列研究成果,详细总结了影响湖泊碳库效应的各种因素,讨论了碳库效应对湖泊沉积物定年结果的影响;分析了目前对湖泊碳库的各类校正方法,包括使用同一测年手段、不同测年材料建立点上碳库大小以及采用不同测年手段对碳库的校正等。本文为湖泊沉积物高精度年代序列的建立提供了一定的参考。

As lake sediment records can provide potentially high-resolution,continuous terrestrial archives of environmental changes,they play an important role in the reconstruction of past climate and environment conditions.Therefore,reliable chronologies are crucial to paleoclimatic studies.Among all dating methods, radiocarbon dating is one of the most useful tools for providing a chronological framework for paleoenvironmental study of lake sediment records.Radiocarbon dating on lake sediments is well known to be very complicated.Accurate chronologies cannot be easily obtained by radiocarbon dating because lack of terrestrial plant macrofossils and suitable dating materials,such as the terrigenous plant residues and charcoal.In fact, the chronology is often established using the organic matter,aquatic debris and various types of shells.However,the reservoir effect that having great influence on the radiocarbon dates with these materials has long been recognized.A closer look at the radiocarbon ages using bulk organic matter and other no-terrestrial macrorests reveals a systematic deviation of the ages on terrestrial plant residue and charcoals.This error has important implications for the resolution of precise event chronologies.In this paper,we review the knowledge from many researches about the reservoir effect in the lake sediment recent years,and detailed summarized the various factors that influenced the radiocarbon dating,discussed how they impact the dating results.We also analysis the current correction method for various types of the reservoir effect in the lake sediments,including the use of same radiocarbon dating method on different dating materials on a given site to find the accurate reservoir effect,and to use various dating methods on the same carbon materials,such as the radiocarbon dating,OSL methods,the 210Pb/137 Cs dating and the U-series dating to measure carbon stocks in the correction and find out the high-precision chronology.We hope our work can give reference for future studies in this area.