湖光岩玛珥湖沉积物硅藻硅同位素研究

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	湖光岩玛珥湖沉积物硅藻硅同位素研究
其他题名	Silicon isotope composition of diatoms in sediments of Lake Huguangyan, South China
	李键
	2008-11-25
学位授予单位	中国科学院地球化学研究所
学位授予地点	地球化学研究所
学位名称	博士
关键词	硅藻硅同位素沉积物古环境代用指标湖光岩玛珥湖
摘要	本论文选取我国的典型玛珥湖－湖光岩玛珥湖为研究对象，在国内外率先系统开展湖泊沉积物硅藻硅同位素研究。为获取过去2000a来的气候环境记录，对原有沉积物-水界面采样装置进行了改进，将沉积物柱芯无扰动采集深度从60cm提高到150cm。建立了一套有效的五阶段硅藻提纯方法，成功从初始硅藻含量大于7%的沉积物中提取出纯度达90％以上的硅藻样品，为广泛开展沉积物硅藻硅氧同位素研究奠定了基础。放射性核素Pb-210、Cs-137、C-14计年结果表明，该湖沉积物堆积速率稳定，具连续、稳定的堆积特点，是气候和环境变化的良好记录体。湖光岩玛珥湖沉积物硅藻硅同位素记录了硅藻利用水体溶解硅的比例变化。沉积物硅藻硅同位素与生物硅含量的变化关系为揭示湖泊古环境提供了重要线索。当硅藻硅同位素组成与生物硅含量呈正相关变化时，湖水溶解硅利用比例主要受温度控制，硅藻硅同位素可反映古温度变化。当硅藻硅同位素组成与生物硅含量不呈相似变化时，湖水溶解硅利用比例主要受有效养分控制，沉积物硅藻硅同位素仅仅反映硅藻利用水体溶解硅的比例，不反映古温度变化。湖光岩玛珥湖沉积物柱芯硅藻硅同位素组成的变化范围为 -0.6‰～1.1‰，其最小值出现于1580～1920年间，指示了1580～1920年为湖光岩地区过去2000年来最冷的时期，为中国南方热带地区现代小冰期的存在提供了新的证据。
其他摘要	Lake Huguangyan, a typical maar lake located in Zhanjiang, Guangdong Province, is selected to carry out a comprehensive study on the silicon isotope compositions of diatoms in sediments. The previous SWB-1 sampling device is improved successfully. The maximum length of sediment cores is increased from 60 cm to 150 cm. Our sampling system prvide an effective way to study the climate/environment change in Lake Huguangyan over the past 2000 years. A continuous five-stage cleaning method is established, which is successfully used to produce diatom samples with >90% diatom content from lake sediments with >7% diatom content. This new procedure makes it possible to study the silicon and oxygen isotope of diatom in more lakes. The dating result by radionuclide Pb-210,Cs-137 and C-14 in Huguangyan sediments indicates the stable sediment accumulation and good preservation conditions in Lake Huguangyan. The silicon isotope composition of diatom silica in Huaungyan sediments record changes in the percentage utilization of dissolved silicic acid by diatoms. The relationship between silicon isotope composition of diatom silica and contents of biogenic silica (BS) provides an important clue to reveal the past environment condition. When silicon isotope composition of diatom silica and BS values are positively correlated, the percentage utilization of dissolved silicic acid by diatoms is dominantly controlled by temperature. When silicon isotope composition of diatom silica and BS values is not correlated, the percentage utilization of dissolved silicic acid by diatoms is mainly controlled by nutrients input. The silicon isotope composition of diatom silica in sediments indicates only the percentage utilization of dissolved silicic acid by diatoms with no implications for temperature. The silicon isotope composition of diatom silica values vary between -0.6‰ and 1.1‰ throughout the sediment core in Lake Huguangyan. There is an obvious shift to the most negative silicon isotope composition of diatom silica values during AD 1580-1920, indicating the coldest period in Lake Huguanguan over the past two thousand years. This provides a new evidence for the existence of the LIA in tropical South China.
页数	97
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3312
专题	研究生_研究生_学位论文
推荐引用方式 GB/T 7714	李键. 湖光岩玛珥湖沉积物硅藻硅同位素研究[D]. 地球化学研究所. 中国科学院地球化学研究所,2008.

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