东平湖沉积物 210Pb、137Cs 垂直分布及年代学意义

对东平湖沉积物柱状岩芯放射性年代学研究表明： 12cm处的 ¹³⁷Cs比活度峰值对应于1963年人工核试验高峰，9cm和6cm处的 ¹³⁷Cs比活度蓄积峰可能分别与1974年的全球核素散落和1986年前苏联切尔诺贝利核电站核泄漏有关； ²¹⁰Pb比活度随深度呈指数衰减，利用 ¹³⁷Cs核素1963年对应的蓄积峰进行校正，采用 ²¹⁰Pb计年的CRS模式建立了1889年以来东平湖现代沉积年代序列。根据 ²¹⁰Pb年代序列，计算了东平湖现代沉积速率，发现近百年来东平湖地区沉积速率有明显变化： 1889～1945年，沉积速率较高，平均达0.297g/cm2?a; 1945～1963年，沉积速率整体处于下降趋势； 1963～2000年，沉积速率比较稳定，平均约0.141g/cm2?a; 约2000年以来，沉积速率有增高趋势。通过分析认为，1945年以前东平湖较高的沉积速率可能与东平湖作为黄河水的自然滞洪区有关； 1950年代国家对东平湖的治理改造，控制了黄河水的自然倒灌，导致了东平湖沉积速率的迅速下降； 1963年以后，由于黄河上中游大型水利工程设施的修建，抑制了东平湖调洪功能的发挥，导致东平湖沉积速率低而稳定； 近年来，东平湖沉积速率有增大趋势，这可能与湖区人民发展围网养殖带入较多的沉积物有关。

VERTICAL DISTRIBUTION AND CHRONOLOGICAL IMPLICATION OF 210Pb AND 137Cs IN SEDIMENTS OF DONGPING LAKE|SHANDONG PROVINCE

The radioactive chronological research on sedimentary cores from Dongping Lake(35°30′～36°20′N,116°00′～116°30′E) shows that the first ¹³⁷Cs special activity peak at the depth of 12cm should correspond to the nuclear bomb test in 1963.The other two peaks at 9cm and 6cm might be related to the global nuclear fallout in 1974 and the leakage of the Chernobyl reactor in 1986，respectively. The specific activity of ²¹⁰Pb decreases exponentially with depth. Correcting by the accumulation peak of 137Cs in 1963，a deposition chronological sequence of Dongping Lake sediments since 1889 was established by the ²¹⁰Pb CRS dating model. According to the chronological sequence，the modern sedimentation rate in Dongping Lake was calculated that had clear changes over the past 100 years: the sedimentary rate was higher during 1889～1945，with an average of 0.297g/cm2?a; showed a declining trend on the whole during 1945～1963; was relatively stable during 1963～2000，with an average of 0.141g/cm2?a; and showed a rising trend since 2000.A higher sedimentary rate since 1945might be related to the fact that Dongping Lake has acted as a natural flood storage basin of the Yellow River. The governmental taming of Dongping Lake in the 1950s controlled the natural flooding of the Yellow River，so its sedimentary rate dropped down rapidly. After 1963，because of construction of large scale hydraulic engineering facilities of the upper and middle Yellow River，the regulating function of Dongping Lake was suppressed，so its sedimentary rate was low and stable. The rising trend of the sedimentary rate in recent years might be related to the development of fence breeding which brought more sediment into Dongping Lake.