利用分子生物标志物-14C技术重建全新世黄海沉积有机质组成变化

Due to high marine primary production and sedimentation rate, abundant marine and terrestrial organic matter was buried in the sediment of marginal sea. The Yellow Sea, influenced by the land-ocean interaction and anthropogenic activity, has a complex source of the organic matters, including marine organic matter, terrestrial biogenetic organic matter and fossil organic matter. These organic matters play different roles in the atmospheric CO2 preservation and cycle, among which the fossil organic matter can be buried over a long period but not contribute to the atmospheric CO2 content. However, the study of the long-term and quantitative reconstruction for the different sources of sedimentary organic matter with different age is still sparse. As a result, the variation rule of sedimentary organic matter in the Yellow Sea is unknown and the influence carbon sink in the Yellow Sea on climate change cannot be estimated. In this study, compound-specific biomarker 14C and 13C isotope will be used to distinguish sedimentary organic matter sources of the Yellow sea during the Holocene: contemporary marine organic matter, contemporary terrestrial biogenetic organic matter, pre-aged organic matter and fossil organic matter. Furthermore, quantitative comparison of reconstruction from 14C and multi-proxy would be used to reveal the variation rule of sedimentary organic matter and indicate the major controlling factors on the variation of sedimentary organic matter during the Holocene. Our study is significant for understanding the relationship between carbon sink effect of the Yellow sea and climate change and the long-term variation mechanism of the sedimentary organic matter.

由于高的生产力和沉积速率，大量有机质被埋藏在边缘陆架海。黄海受陆-海相互作用及人类活动影响，有机质来源复杂，可以分为海源有机质、陆地生源有机质和古老有机质，这三类有机质对于大气CO2的储存和循环具有不同的作用，其中古老有机碳埋藏可长期保存但不影响大气CO2含量。但目前还缺乏黄海沉积有机质中不同年龄有机质的演变记录，制约定量估算其对碳收支的贡献。在本研究中，申请人拟利用分子生物标志物14C和13C同位素技术，定量重建全新世黄海沉积物中不同年龄有机质的组成变化(当代海源有机质、当代陆地生源有机质、陈化有机质(pre-aged)及古老有机质)，并探讨与多参数指标重建的不同源有机质的记录(陆地植物有机质、土壤有机质和海源有机质)记录的关系，定量评估全新世黄海沉积有机质的组成变化及其对气候变化的影响。研究结果对于揭示黄海长期碳汇效应，深入了解黄海沉积有机质变化机制有重要意义。

陆架边缘海是陆源有机质重要碳汇，不同来源和不同年龄有机质在不同时间尺度具有不同的碳汇意义。全新世以来，全球海平面发生明显的变化，我国东部陆架海洋生态环境及沉积有机质的组成也发生了明显的改变。总体而言，我国东海陆架现代和近代沉积有机质的组成比较明确：东海陆架71个表层沉积物Δ14C分布范围是-575.4‰~-208.7‰（对应着2000-7000 yr BP），显示古老有机质和/或陈化有机质的广泛存在。长江水体输送POC相对年轻（<1000 yr BP），而古老有机质相对比例%fossil高于陆源有机质%TOM，显示再悬浮和再沉积过程可能是表层沉积有机质相对较老的控制因素之一。但是目前对于千年时间尺度的格局存在非常大的不确定性。本研究选取济州岛西南泥质区三个柱状样，定量估算了全新世以来沉积有机质的组成，并对其来源和搬运途径进行了探讨：早全新世具有相对高比例的TOM（平均为70%），而在中晚全新世，TOM相对贡献明显降低（平均为22%）；古老有机质的相对比例早全新世%fossil较高（平均为37%），而中晚全新世其比例有所降低（平均为28%）的趋势。这主要是由于早全新世，河流直接输入陆源物质；而在中晚全新世，现代环流体系形成，海洋生产力贡献了高的海源有机质所导致。另外，早全新世，%fossil（平均为37%）明显低于%TOM（平均为70%）；而在中晚全新世，%fossil（平均为28%）相对高于%TOM（平均为22%）。可能是在低海平面阶段，河流直接搬运陆源有机质至济州岛西南区域，保留了源区信号；而在中晚全新世，现代环流体系的形成，TOM和fossil主要来源于区域环流的再悬浮和再沉积，改造了源区信号，使得部分有机质年龄年老，但并未明显改变TOM的信号，因此导致%fossil相对高于%TOM。研究结果对于揭示我国东部陆架海长期碳汇效应，深入了解东海沉积有机质变化机制有重要意义。