利用支链GDGT和14C追踪西北冰洋沉积物中的陆源有机物

Rapid environmental changes have been occurred in the Arctic in recently years, such as significant reduction in sea-ice cover, accelerated degradation of permafrost, increased river freshwater input, increased coastal erosion. These would result in changes in the composition and burial efficiency of sedimentary organic carbon in the Arctic Ocean.The focus of this research project is to clarify the source of sedimentary organic carbon in the Western Arctic Ocean.The suspended particles,ice core samples taken from drill, the time series sediment trap samples and multicore sediments will be collected in the Western Arctic Ocean, including the Chukchi Sea, the Beaufort Sea and the Canada Basin. And bulk organic carbon parameters (C/N ratio and 13C), BIT index and ?14C will be measured in these samples. A three- end mixing model will be used to assess the terrestrial contribution to the total sedimentary organic carbon, and the fractional abundances of plant source andsoil source,as well as the fractional abundances of modern and 'pre-aged' source in the terrestrail contribution.The variations of sedimenatray organic carbon composition and structure in Western Arctic Ocean and its response to global climate chang will be discussed in this research.This project is an important supplementation to the study of biogeochemical cycling of sedimentary organic carbon in the Western Arctic ocean and will provide valuable data for correctly estimate carbon budgets in the Western Arctic ocean. It is also helpful for correctly assess the organic carbon burial efficiency in marginal seas, and is of great significance for global carbon cycle research.

近年来，北极发生了快速变化。海冰覆盖面积大幅度减少、周边冻土层加速退化、河流淡水输入增加、沿岸侵蚀加剧。这些变化将使北冰洋埋藏的沉积有机碳组成结构产生变化。本项目以西北冰洋楚科奇海-波弗特海-加拿大海盆为研究对象，以海水悬浮颗粒、海冰钻孔、时间系列沉积物捕获器样品、多管沉积物短柱为材料，利用表征有机碳来源的整体性示踪参数C/N，13C，结合表征土壤来源的BIT指数和表征古老有机质的?14C，来研究西北冰洋沉积有机碳的来源。使用三端元混合模型来评估陆地来源有机碳的贡献，区分陆源有机质中植被有机碳、土壤来源有机碳以及这些陆源有机碳中的古老有机碳。探讨全球变化条件下，西北冰洋沉积有机碳的组成与结构变化及其对气候变化的响应。项目的实施是西北冰洋沉积有机碳生物地球化学循环研究的重要补充，将为正确估算北冰洋碳收支和评估提供数据支持。有助于我们正确评估边缘海有机碳埋藏效率，对全球碳循环研究具有重要意义。

北极快速变化造成的北极周边广袤的冻土层迅速退化、沿海侵蚀加强、河流沉积输入增加，导致大量陆源有机质输入北冰洋；同时，海冰消退，太平洋入流增加，河流输入增加，携带大量的营养物质进入北冰洋，改变北冰洋上层“生物泵”结构。这些过程必将会在较短时间尺度内引起北冰洋沉积物有机碳组成结构和埋藏效率的变化。本项目以西北冰洋楚科奇海-波弗特海-加拿大海盆为研究对象，参加了两次北极科学考察，结合历次中国北极科学考察采集的样品，以海水悬浮颗粒、海冰钻孔、时间系列沉积物捕获器样品、表层沉积物样品、多管沉积物短柱为材料，利用表征有机碳来源的整体性示踪参数C/N，δ13C，结合表征土壤来源的BIT 指数和表征古老有机质的Δ14C以及表征海洋生产力和“生物泵”结构的生物标志物绿素，光合色素，类脂物等，研究了西北冰洋沉积有机碳的来源，同时也分析了上层海洋生物泵结构及其影响因素。结果表明，在楚科奇海上层海洋生物泵结构主要受太平洋入流的影响，在陆架水影响区域生物量高且以硅藻为主，在阿拉斯加沿岸流（ACW）影响区域以甲藻为主。而在海盆区生物泵结构以微藻和薇薇藻为主，受到海冰消融和开阔海域出露时间的显著影响。楚科奇海沉积有机碳组成自中陆架向阿拉斯加沿岸和海盆区，陆源有机质比重增加；Δ14C结果表明，在陆坡区有古老沉积物埋藏信号。利用N/C，δ13C，BIT指数以及木质素端元分析结果表明，楚科奇海沉积有机质海洋来源占58%， 而土壤来源和植被来源分别为13%和29%。白令海沉积有机碳陆源有机质含量则在18.9%-99.6%。表明陆源有机质是北冰洋太平洋扇区沉积有机碳的重要组成部分。