内蒙古乌梁素海^210Pb和^137Cs测年与现代沉积速率

^(210)Pb and ^(137)Cs Dating and Modern Sedimentation Rate on the Wuliangsu Lake of Inner Mongolia

对乌梁素海沉积物柱心样品进行210Pb、137Cs测年分析表明,柱心剖面上有明显的1963年蓄积峰,这个蓄积峰对乌梁素海的现代沉积有明显的时标意义。根据210Pb的CRS模式,可以计算出每个样品深度所对应的年代,在该沉积柱心中与137Cs时标吻合较好。乌梁素海的沉积速率并不稳定,变化比较大,表明乌梁素海近113 a来沉积环境不稳定。210Pb、137Cs两种计年方法的结合有助于认识沉积速率变化较大的沼泽的沉积状况,也有助于对核素计年方法的理解。

Environmental 210pb and 137Cs dating techniques were applied to determine recent deposition rates. 210pb and 137Cs were analyzed for the Wuliangsu lake sediment core. In the core, there was an obvious peak in 1963, which was an important age characteristic for the Wuliangsu lake sediments. The deposition rate of the Wuliangsu lake was about 0. 47 cm/a by 137Cs time marker（1963）. 210 Pb （CRS） dating showed a relatively good agreement with the 137Cs dating. The limit depth of 210pb was 74 cm, which corresponded to the year of 1892. The abnormal variations of 210pb activity could be found in the profile. The highest value of 210pb at the depth of 20 cm might be linked with the maximum value in 1963 due to the nuclear bomb test producing both 137Cs and 210Pb. The deposition rate was changeable in the Wuliangsu lake by analyzing the depth and ages, which showed that the sedimentation environment was changeable in recent 113 years either. The combination of the two dating methods was useful to understand the substantial sedimentation process of the wetland where sedi- mentation rates change rapidly.