Abstract
云南省沪沽湖、洱海<sup>210</sup>Pb<sub>ex</sub>的垂直分布受 Fe、Mn循环下<sup>210</sup>Po和<sup>210</sup>Pb沉积后再迁移的影响,分别表现为三种不同的剖面分布特征.<sup>210</sup>Pb<sub>ex</sub>计年的沉积物堆积速率分别为0.050-0.051g·cm<sup>-2</sup>a<sup>-1</sup>和0.044-0.045g·cm<sup>-2</sup>a<sup>-1</sup>,反映百年时间尺度上的堆积结果.沪沽湖、洱海<sup>137</sup><sub>Cs</sub>的垂直剖面分布虽然受分子扩散作用的影响,但并没有改变其峰值位置.沪沽湖深水湖区<sup>137</sup>Cs计年的沉积物堆积速率为0.045 ± 0 004g·cm<sup>-2</sup>a<sup>-1</sup>(1964年时标).按不同时标,洱海<sup>137</sup><sub>Cs</sub>计年的沉积物堆积速率为对.048±0.0039·cm<sup>-2</sup>a<sup>-1</sup>(1964年时标),0.047 ± 0.0029·cm<sup>-2</sup>a<sup>-1</sup>(1975年时标),0.046±0 005g·cm<sup>-2</sup>a<sup>-1</sup>(1986年时标).三种时标给出的沉积物堆积速率一致,其平均值为0.047±0.0029·cm<sup>-2</sup>a<sup>-1</sup>,与<sup>210</sup>Pb<sub>ex</sub>计年方法获得的数值吻合.;Two plateau lakes (Lugu Lake and Erhai Lake) with different conditions are selected to show 210Pb geochemical behavior. <sup>210</sup>Pb and <sup>137</sup>Cs vertical profiles in sediments are measured by the Multichannel Analysis System (Caberra 100) in order to attain creditable sediment accumulation rates. By the Fe-Mn circulation, <sup>210</sup>Pb<sub>ex</sub> vertical distribution in the sediments of Lugu Lake and Erhai Lake shows three types of distribution characteristics. But this has no influence on the <sup>210</sup>Pb<sub>ex</sub> dating result. Sediment accumulation rates of Lugu Lake and Erhai Lake are 0. 050 -0.051 g·cm a and 0.044 -0.045 g· cm<sup>-2</sup>a<sup>-1</sup> respectively by <sup>210</sup>Pb<sub>ex</sub> method which repsents the average sediment accumulation result on 100-year scale. The discrepancy between the <sup>137</sup>Cs vertical distribution characteristics and the depositional fluxes is probably caused by the Cs diffusion in early-diagenesis process. However, the Cs diffusion does not change the location of Cs peaks. Sediment accumulation rate of Lugu Lake is 0. 045 土 0. 004g · cm<sup>-2</sup>a<sup>-1</sup> by <sup>137</sup>Cs time marker (1964), and that of Erhai Lake is 0. 048 ± 0. 003g·cm<sup>-2</sup>a<sup>-1</sup> (1964), 0. 047 ± 0. 002g-cm<sup>-2</sup>a<sup>-1</sup>(1975), and 0. 046 ± 0. 005g· cm<sup>-2</sup>a<sup>-1</sup>(1986) respectively which reflects the average sediment accumulation result.
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