Environmental Changes Inferred from Environmentally Sensitive Grainsize Component Records in Chaiwopu Lake, Xinjiang
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摘要: 通过对柴窝堡湖沉积物剖面和流域表层沉积物进行粒度分析，结合沉积剖面年代序列，研究了柴窝堡地区的环境演变与沙尘暴事件。首先通过主成分因子分析，对柴窝堡湖沉积物剖面粒度不同粒级组分含量进行了研究，探讨了湖泊沉积物的物质来源，获得了两个主控因子F1和F2，它们控制了湖泊沉积物近97.7%的粒度变化特征。研究表明，F2代表了以57 μm为众数粒径的次总体，主要来源于地表风沙侵蚀；而F1为以7 μm为众数粒径的次总体，主要受流水作用控制。进而通过粒径—标准偏差法，提取了湖泊沉积物中环境敏感粒度组分，风成组分C2（20~209 μm）反映了区域风沙活动的历史，并揭示了1910—1930年和1980—2000年为百年来的两个沙尘暴相对活动强烈的时期。沉积物中记录的1980年和2000年左右的沙尘事件与器测记录及历史文献记载具有很好的一致性。最后利用均值突变诊断分析，发现柴窝堡湖地区1910年前后存在近百年来最强的沙尘事件，揭示了近百年来该地区一次最强的环境突变事件。 Abstract: Grainsize analysis of a sediment core CW02 and surface sediments of the drainage area, retrieved from Chaiwopu Lake of Xinjiang, were carried out using a Malvern 2 000 grainsize analyzer. Combining with 137Cs dating, a continuous highresolution record of environmental changes was studied over the past 150 years. Firstly, according to primary components analysis of the contents of different grainsize, the material source of lake sediment was discussed. It showed that the large particle fraction of lake sediment was from the drainage surface sediment. And then, environmentally sensitive grainsize components were extracted by the variations of the grainsize standard deviation. The results indicated that the content/meansize of sensitive grainsize component (20~209 μm) is sensitive to the regional sanddust storm events in Chaiwopu lake basin. During the last 150 years, the strong sanddust storm occurred during 1910—1930AD and 1980—2000AD. Historical documents also recorded the strong dust storms around 1910s and 1980s. Based on the analysis of the abrupt change points, the sediment grainsize increased abruptly around 1910AD, which indicated an abrupt environmental event.
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Key words:
- Chaiwopu Lake /
- lake sediment /
- grain size /
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sensitive components
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