青藏高原典型季风区有机质埋藏记录和碳库效应研究

By establishing the occurrence characteristics and scale of organic matter buried in sediment of typical basin in the East Asian monsoon, Tibetan Plateau, and combining the alkenonesδ13C in the typical lacustrine sediments of Tibetan Plateau as well as the carbon dioxide atmospheric concentration estimated using the differential value between the alkenonesδ13C and carbon dioxide δ13C dissolved in water, and then inversion the organic matter original burial flux of modern sediment in Tibetan Plateau of typical monsoon region. Study the relationship between the organic matter changes and the potential carbon-containing gases from organic matter buried in sediment, using the data obtained from immature-nature organic samples with low temperature pyrolysis experiment. Through the analysis of organic carbon content and carbon isotopic composition of sediments on typical basin sedimentary sequence (about 30Ma) since Cenozoic, try to establish the quantitative relation between different maturity organic matters and carbon-containing gases into the carbon reservoir, and study the reservoir effect stimulated in the sedimentary basin, then to provide evidences for exploring the effect of the Tibetan Plateau uplift to the global carbon cycle and climate change.

通过建立青藏高原东亚季风区典型盆地沉积物中有机质的赋存特点和含碳气体排放规模，结合湖泊沉积物中长链不饱和烯酮单体同位素获得的有机质原始埋藏通量校正参数，并利用有机质低温热解模拟实验数据，计算和反演青藏高原典型季风区沉积序列(约30Ma)原始有机质埋藏通量和含碳气体排放通量；深入剖析在埋藏过程中有机质的变化和含碳气体排放之间的内在关系，探讨沉积盆地中激发的碳库效应，并与新生代以来重大冷暖气候事件相结合，对历来被认为是“永久性”埋藏而未开展工作的低熟有机质在全球碳循环和环境演化过程中的重要作用进行重新认识,为青藏高原构造隆升对全球碳循环和气候的影响提供科学依据。

本项目以青藏高原东北部克鲁克湖湖泊钻孔沉积物为研究对象，通过野外地质观测和样品采集，借助现代有机地球化学理论和分析研究方法，系统开展了青藏高原东北缘末次冰消期以来的古气候环境的研究。并通过对湖泊沉积物中长链不饱和烯酮单体同位素的系统分析，获得了有机质原始埋藏通量校正参数，结合青藏高原东北缘西宁-谢家剖面有机质低温模拟实验数据，反演了青藏高原东亚季风区沉积序列原始有机质埋藏通量和含碳气体排放通量，阐明了埋藏过程中有机质的变化和含碳气体排放之间的内在关系，探讨沉积盆地中激发的碳库效应。研究结果显示，青藏高原东北缘东亚季风区西宁盆地沉积物在地史时期CO2排放量约为18-8224ml/kg样品，均值为2461ml/kg样品，CH4的排放量约为1-19ml/kg样品，均值为6ml/kg样品，原始有机碳埋藏通量约为0.01-0.16t/(Mam2)，均值为0.03t/(Mam2)。通过新生代以来重大气候事件对比分析，研究发现原始有机碳埋藏通量的大小与地史时期典型冷暖气候环境特征有一定的相关性，即当气候环境较为温暖干燥时，含碳气体排放量和原始有机碳埋藏量都呈现高值；而当气候条件转向冷湿时，原始有机碳埋藏通量和含碳气体排放量都处于低值。研究结果也表明，通过对浅层埋藏沉积物含碳气体排放量和原始有机碳埋藏通量特征的分析，可以捕获地史时期发生的典型冷暖气候变化事件。本研究对历来被认为是“永久性”埋藏而未开展工作的低熟有机质在全球碳循环和环境演化过程中的重要作用进行了重新认识，为青藏高原构造隆升对全球碳循环和气候的影响提供了重要的科学依据。