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古洪水研究是近几十年来全球变化研究的一个热点,同时也是难点。本文利用赣北黄茅潭的湖泊沉积,建立了小冰期以来全球变暖背景下的区域洪水记录。采用210Pb和137Cs方法厘定了地层年代,基于粒度与元素地球化学指标的对比分析,揭示了器测记录(1950年)以来指标记录的特点与区域日降水超过50 mm天数的关系,认为黄茅潭HMT-01孔粒度(包括粗粉砂+砂/粘土比值、平均粒径)和Zr/Rb、Ti/Rb、Zr/Fe比值可作为洪水指标记录,共识别出1950-2010年期间记载的13次洪水事件中的11次。基于这些指标记录及指标特点,共识别1769-1950年间由历史文献记录的31次洪水事件中的23次,识别率达74.2%。研究表明:(1)湖泊沉积中Zr/Rb、Ti/Rb、Zr/Fe比值和粒度参数(平均粒径、粗粉砂+砂/粘土)作为洪水指标,对洪水事件沉积有较好的指示作用,且Zr/Rb比值对洪水事件的检出率较高;(2)黄茅潭流域洪水发生频率暖期高于冷期;(3)年代际尺度上,1820s-1840s,1860s-1870s为19世纪冷期黄茅潭洪水高频期,这两个阶段对应东亚夏季风偏强,长江中下游地区降雨较多;20世纪赣北黄茅潭洪水基本随1920s-1940s,1980s-1990s两个变暖阶段而高频出现,与长江中下游大洪水演变特点基本一致。研究结果为利用湖泊沉积记录反演过去的洪水变化,延长洪水序列、认识洪水规律提供了一定的科学依据。
The study of paleo-floods has been a hot and difficult point in the study of global change in recent decades. In this paper, we use the lake sediments in Huangmaitan, northern Jiangxi Province to establish a regional flood record in the context of global warming since the Little Ice Age. Using 210Pb and 137Cs methods to determine the age of the strata, based on the analysis of the grain size and elemental geochemical indicators, the relationship between the characteristics of the indices recorded since the test records (1950) and the daily precipitation over 50 mm in the region was revealed. The pore size of HMT-01 (including coarse silt + sand / clay ratio, average particle size) and the ratios of Zr / Rb, Ti / Rb and Zr / Fe can be recorded as flood indicators, identifying 13 11 times in the flood event. Based on the records of these indicators and the characteristics of the indicators, 23 out of 31 flood events recorded by historical records from 1769 to 1950 were identified, with a recognition rate of 74.2%. The results show that: (1) Zr / Rb, Ti / Rb, Zr / Fe ratios and particle size parameters (average particle size, coarse silt + sand / clay) in lakes are used as flood indicators, (2) The frequency of flood occurrence in Huangmaitan Basin is higher than that in cold period; (3) On the decadal scale, 1820s-1840s and 1860s-1870s The high temperature period of the Huang Maotan flood during the 19th century, corresponding to the stronger East Asian summer monsoon and more rainfall in the middle and lower reaches of the Yangtze River. In the 20th century, Huangmaitan Lake in the north of Jiangxi Province experienced two floods from 1920s to 1940s and 1980s to 1990s The warming stage appeared at high frequency, which was consistent with the evolution of the flood in the middle and lower reaches of the Yangtze River. The results provide some scientific evidences for using lake sediment records to retrieve past flood changes, extend flood sequences and recognize flood laws.