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对赣北黄茅潭近代湖泊沉积岩芯进行了~(137)Cs、~(210)Pb测试和SCP(球状碳粒)计数分析,阐述了~(137)Cs蓄积特征,结合SCP计数、粒度指标及降水记录厘定了一些事件性沉积层位。研究表明,1986年前后是沉积环境中~(137)Cs行为的转折点;在这之前,~(137)Cs以大气散落为主,其蓄积行为大致与降水存在正相关关系,在这之后,~(137)Cs以流域侵蚀为主,其蓄积行为与降水呈负相关关系。1953—1954年、1974—1975年、1998—1999年,流域降水丰沛,相应沉积层位~(137)Cs比活度低,这与流域强烈侵蚀稀释了进入湖泊的~(137)Cs有关。1963—1964年沉积层位~(137)Cs蓄积峰稳定而显著,与高通量的大气散落有关,也与当时降水量低,大雨、暴雨次数少,流域侵蚀强度低造成较低的沉积速率等密切相关,是可靠的定年时标。1986年存在同样的气候环境特点,其蓄积峰可能也是存在的,但需要进一步确认。基于~(210)Pb方法,利用多种计年模式计算了沉积岩芯的年代,发现与这些事件性沉积层位具有较大差异。研究认为,在长江中游这种降水高、流域侵蚀强度高的较为复杂的沉积环境中,~(210)Pb计年存在较大误差。复杂沉积环境中近代沉积的定年,有必要深度挖掘~(137)Cs环境行为,在全面阐述其蓄积特点的基础上,辅以SCP计数、粒度指标及降水等识别事件性沉积层位,矫正~(210)Pb计年,是精确建立近代沉积时标的必要方法。
The 137Cs and 210Cb Pb isotopes and SCP counting were analyzed for sedimentary cores of modern lakes in Huangmaitan, northern Jiangxi Province. The characteristics of 137Cs accumulation were described, and the combination of SCP count, grain size index And precipitation records determine some eventual sedimentary horizon. The results show that before and after 1986 was the turning point of 137Cs activity in sedimentary environment. Until now, ~ (137) Cs was mainly scattered in the atmosphere, and its accumulation behavior had a positive correlation with precipitation. After that, ~ (137) Cs is dominated by watershed erosion, and its accumulation behavior is negatively correlated with precipitation. In 1953-1954, 1974-1975 and 1998-1999, the precipitation in the drainage basin was abundant, and the specific activity of 137 Cs in the corresponding sedimentary horizon was lower than that of 137 Cs in the watershed. The accumulation peak of ~ (137) Cs in the sedimentary horizon was stable and significant from 1963 to 1964, which was related to the high flux of scattered air and low deposition rate at that time with low rainfall, heavy rains and heavy rainfalls and low erosion intensity Is closely related, is a reliable time scale. The same climate and environment characteristics existed in 1986, and the accumulation peak may exist, but further confirmation is needed. Based on the ~ (210) Pb method, the dating of sedimentary cores was calculated using various dating models and found to be quite different from these event-sedimentary horizon. The study suggests that there is a big error in the dating of ~ (210) Pb in the more complex sedimentary environment with high precipitation and high erosion intensity in the middle reaches of the Yangtze River. In the complex depositional environment, it is necessary to excavate the environmental behavior of ~ (137) Cs deeply in the modern depositional dating. Based on the comprehensive description of its accumulation characteristics, together with SCP count, grain size index and precipitation, (210) Pb dating is a necessary way to accurately establish a modern deposition time scale.