长江口泥质区18~#柱样的现代沉积速率及其环境指示意义

Modern sedimentation rate and its implications for environmental evolutions of the 18~# core in the Changjiang Estuary in China

通过对长江口泥质区18#柱样进行137Cs和210Pb同位素测年分析,得到了柱样站点的现代沉积速率。结果表明,近50多年来沉积速率较大,且呈现阶段性差异:由137Cs时标计年法得到柱样1954—1964年的沉积速率为5.9 cm/yr,1964—2006年减小为3.36 cm/yr;沉积柱样的210Pb剖面呈两段分布,由此得到沉积速率120～225 cm为5.47 cm/yr,对应于18～100 cm减小为4.58 cm/yr。对比分析两种方法得出沉积速率开始减小的时间为1968—1972年,并且采样点区域表层可能出现侵蚀现象,为研究长江口泥质区环境演变提供了依据。

The 18# core collected in Yangtze River Estuary was analyzed for 137Cs and 210Pb Radioisotope measurement.The results showed that,sedimentation rate in recent 50 years was large and could be divided into some distinct stages： sedimentation rate calculated from 137Cs method was 5.9 cm/yr during 1954-1964,while reduced to 3.36 cm/yr during 1964-2006.Two parts of the graph showed a good exponential decay in the 210Pb profile of the 18# core.Sedimentation rate is 5.47 cm/yr during 120~225 cm,and corresponds to 4.58 cm/yr during 18~100 cm.It can be found that erosion occurs in this area through analyzing the results of two methods maybe,and sedimentation rate decreases from 1968-1972.The paper provides a basis for studying on the environmental evolution of the Yangtze River Estuary.