摘要
通过对云南滇池沉积物柱芯DC1样品的放射性核素137Cs和210Pb测试分析,发现该柱芯137Cs自1954年首次沉降以来存在1963年、1975年和1986年三个较为明显的蓄积峰,获得滇池自137Cs相应的时标年份到2007年的平均沉积速率分别为0.062g/cm2.a-1、0.051g/cm2.a-1、0.049g/cm2.a-1和0.043g/cm2.a-1。借助210Pb CRS计年模式,获得滇池过去159年间的沉积速率是不稳定的,整体上呈现先升高后降低的趋势。这种不稳定的沉积环境,可能与滇池地区相应历史时期的人类活动有密切关系。对两种计年结果产生差异的可能原因进行了探讨。对比分析了沉积物柱芯DC1相应时段颗粒的中值粒径和当地距今50多年的降雨资料变化关系,发现滇池沉积物粒度的中值粒径与该地区降雨量呈现出良好的同步波动。在短时间尺度、高分辨率(10a、年际)的研究中,沉积物粒度的中值粒径可以有效地指示湖区降雨量的大小变化。
Based on radionuclide dating （210 Pb and 137Cs） in the sediment core of the Dianchi Lake, Yunnan Province of China, we calculated the sedimentation rates in the past 159 years. The vertical profile of 137 Cs has three obvious 137Cs peaks in the core corresponding to 1963, 1975 and 1986, since the onset of 137Cs fallout in 1954. Using the dating of the 137Cs peaks, the four time-averaged accumulation rates of the Dianchi Lake were 0. 062, 0. 051, 0. 049 and 0. 043 g/cm2 · a-1 , respectively. Four stages with different accumula- tion rates in core DC1 indicated a slower process since the onset of atmospheric nuclear weapons testing in the 1954. According to the result of 210Pb （CRS） dating in DCl, the sedimentation rate is 0. 052 g/cm2· a-1 , which is unstable in the past 129 years, which might be related to human activities during different historical periods of the past 100--150 years. As for dissimilar physical and chemical associations, diffusion characteristics for the two radionuclides （Pb and Cs）, we interpreted the rationality of deviation by the two dat- ing methods. The further precise result can be obtained by combining two or more dating methods, respectively. Compared with the local rainfall in the past 50 years with sediment grain size in the region of Dianehi Lake, it is found that there was an obvious variation trend in the sediment grain size with the fluctuations of rainfall. All these findings indicate that there is a positive correlation between grain size and the fluctuations of rainfall. This shows that sediment grain size could reflect the rainfall changes trend at a short time-scale and high resolution investigations, i.e. larger sediment grain size reflected more rainfall and wetter climate while smaller sediment grain size reflected less rainfall and drier elimate.
出处
《地理研究》
CSCD
北大核心
2011年第1期161-171,共11页
Geographical Research
基金
国家自然科学基金项目(40873071
41030751)
江苏省高校自然科学研究重大项目(09KJA170002)
南京师范大学优秀博士学位论文培育基金项目(1243211601039)
关键词
放射性核素
沉积速率
粒度
气候干湿
滇池
radionuclide dating （210Pb and 137Cs）
sedimentation rate
grain size
wet anddry climate
Dianchi Lake
