植被与气候变化在我国渤、黄、东海陆架泥质区中的木质素分子化石和稳定同位素沉积记录

Marginal seas are playing critical roles to global carbon cycle and climate change because of their high productvity and burial of oragnic carbon. However, the quantitative understanding for the carbon budget of the marginal seas is very poor since they are strongly influenced by land-sea interaction and human activities, in addition to the apparent lack of observation data. Especially, the input and burial of huge amount of terristrial organic carbon (TOC) to the marginal seas are very unclear. This is particularly true for marginal China Seas. Marine sediment is a very good carrier for long-term and relative continuous records for the burial of TOC. It therefore can be used for reconstruction of the variation trend of TOC in the past, and for inversion of the response of land vegetation to climate change, which provides important basics for predicting the influence of climate change to organic carbon cycle and land vegetation in the future. This project will try to estimate the contribution of TOC to the total organic carbon buried, and to evaluate quantitatively the contribution of terrestrial end-members to TOC, through determination of lignin molecular fossil and the related parameters, the δ13C in lignin monomers, as well as the total organic content and its C/N ratio, δ13C and δ15N in sediment samples collected in Bohai, Yellow Sea and East China Sea. Based on these observation data, we will try to understand the response of land vegetation in different drainage basins of Yellow River and Yangtze River to the climate change before and after the industrial revolution in China, by reconstructing and comparing the long-term depositional records in different sediment columns. Through this project, we expect to reveal the historical disciplinarian, and thus to provide insights for predicting the variation trends in the future.

由于其高的生产力和有机碳埋藏，陆架边缘海对全球碳循环和气候变化有着极其重要的作用。但受强烈陆海相互作用和人类活动影响，加之观测资料匮乏，目前对其碳收支的定量了解非常缺乏。其中大量陆源有机碳（TOC）向陆架边缘海输入与埋藏的情况尤其不清楚，我国陆架边缘海更是如此。沉积物保存着长期且较为连续的TOC埋藏记录，可用于重建过去变化趋势，反演陆源植被对气候变化的响应，为预测未来气候变化对陆源植被和有机碳循环的影响提供必要数据。本项目将通过测定渤、黄、东海沉积物样品中木质素分子化石参数、总有机质含量及其C/N比、δ13C和δ15N，以及木质素单体的δ13C，估算TOC对埋藏的总有机碳的贡献，并定量估算各陆源植被单元对TOC的贡献率。在此基础上，通过重建TOC的长时间沉积记录，并比较各柱状样的不同，研究工业革命前后以及黄河和长江流域陆源植被对气候变化的响应，揭示历史变化规律，预测未来变化趋势。

本项目首先改进和优化了海洋沉积物中木质素的分析方法，然后通过测定（和计算）渤、黄、东海沉积物样品中的木质素氧化产物和相关参数，获取了木质素的植被参数、降解参数等的分布特征；并结合其他有机地球化学指标（包括总有机质 C/N、总有机质 δ13C、粒径等），探讨了陆源有机物的来源、降解程度以及陆源有机碳（TerOC）对埋藏在渤、黄、东海陆架区总有机碳的贡献。借助柱状沉积物中木质素的垂直分布特征，重建了TerOC的沉积记录，探讨了影响陆源有机物来源、迁移和埋藏的因素。并比较了不同海域各柱状样的差异，研究了不同流域陆源植被对气候变化的响应，为预测未来气候变化的影响提供了科学依据。另外，我们通过对南黄海泥质区各柱样高分辨率木质素沉积记录的分析，探讨了全新世以来木质素参数的潜在变化机制及其对古环境演变的响应关系。研究结果显示，在陆架边缘海沉积物木质素记录的特征变化中，气候因子（本项目中主要指东亚冬季风（EAWM）和厄尔尼诺-南方涛动（ENSO））驱动的水动力分选作用起到根本性的控制作用，而受东亚夏季风（EASM）驱动的物源区植被类型变化并不是主要的控制因素。全新世时期，柱样中木质素沉积记录结果显示在百年尺度上，其与“Bond 冷事件”和EAWM之间存在明显的关联，而千年尺度上的长时期变化趋势，主要受ENSO的控制。从研究结果我们可以得出结论，木质素指标可以作为古气候演变的可靠指标。