南海东北部上层沉积物有机碳的沉积特征

南海北部拥有陆架?陆坡体系中最不稳定的峡谷群沉积环境，不仅是海洋有机碳沉积区域，更是陆架和深海之间物质传输的通道。于2019年和2020年分别采集一统峡谷和东沙群岛海域陆坡的上层沉积物样品（0～30 cm），研究其有机碳含量和红外光谱吸收强度的垂直分布特征，探讨陆坡环境有机碳的迁移和沉积规律。结果表明，一统峡谷上层沉积物中有机碳含量由坡上、坡中至坡下逐渐降低，依次为1.14%～2.02%、1.01%～1.46%和0.60%～2.15%；东沙群岛海域陆坡上层沉积物中有机碳含量为0.52%～1.35%；4个站位有机碳的垂直变化不具有相似性。研究区域上层沉积物中有机物的红外光谱吸收呈现500～1500 /cm、2300～2500 /cm和3400～4000 /cm 3个集中出峰区；一统峡谷坡上沉积物中有机物红外光谱吸收特征与坡下相近，吸收强度均随深度增加而降低，坡中沉积物中有机物红外光谱吸收强度随深度变化不显著；东沙群岛海域沉积物中有机官能团的红外吸收率在中间层次出现突然增加的现象。研究区域峡谷沉积物中有机物主要由相邻峡谷坡上通过滑坡碎屑流直接运移到坡下，在坡中难以稳定存留；坡中沉积物中有机物被不断扰动而上下混合，其组成的垂直分布较为均匀。

Sedimentary characteristics of organic carbon in upper sediments of the Northeastern South China Sea

The north of the South China Sea has the most unstable Valley Group sedimentary environment in the shelf slope system. It is not only a marine organic carbon deposition area, but also a channel for material transfer between the shelf and the deep sea. In this study, the upper sediment samples (0～30 cm) of Yitong gorge and Dongsha Islands sea slope were collected in 2019 and 2020 respectively to study the vertical distribution characteristics of organic carbon content and infrared absorption intensity, and to explore the migration and deposition of organic carbon in the slope environment. The results show that the organic carbon content in the upper sediments of Yitong gorge gradually decreases from the upper slope, middle slope to the lower slope, which are 1.14%～2.02%, 1.01%～1.46% and 0.60%～2.15% respectively. The organic carbon content in the upper sediments of Dongsha Islands sea area is 0.52%～1.35%; the vertical variation of organic carbon in the four stations was not similar. The infrared absorption spectra of organic matter in the upper sediments of the study area showed three peak areas: 500～1500 /cm, 2300～2500 /cm and 3400～4000 /cm; the results show that the infrared absorption characteristics of organic matter on the slope of Yitong gorge are similar to those under the slope, and the absorption intensity decreases with the depth, while the infrared absorption intensity of organic matter in the slope does not change significantly with the depth; the infrared absorptivity of organic functional groups in Dongsha Islands sea area increased abruptly in the middle layer. During the migration process of organic matter in the canyon sediments in the study area, the organic matter directly migrated from the adjacent Canyon slope to the slope through landslide debris flow, which was difficult to remain in the slope. The vertical distribution of organic matter in the slope is more uniform.