近百年来长江入海沉积物在南黄海中部的沉积记录及其输运机制研究

The sediments discharged from the Changjiang (Yangtze) River are an important source in the South Yellow Sea (SYS). The provenance discrimination of Changjiang sediments and identification of the transport mechanism in the central SYS, have important scientific significance to the in-depth understanding of sediment diffusion system and characteristics of land-sea interaction in the continental margins of China. In this study, after measuring the sedimentation rates of six sediment cores in the central SYS, the samples in the last century sedimentary layers would be collected. By testing and analyzing minerals and elements, the mineral and element compositions of the sediments as well as the provenance would be discriminated. Meanwhile, with comprehensive analysis of the minerals and elements of the suspended matters collected in the SYS in summer and winter, the provenance of suspended matters in different seasons would be discriminated, and the distribution and migration of Changjiang substances would be tracked. From the study, the distribution characteristics of Changjiang substances in the central SYS during the past century would be discriminated, the distribution and transport of Changjiang sediments in the SYS under the influence of seasonal circulation system would be revealed, moreover, the transport mechanism of Changjiang substances would be explained reasonably combined with water mass analysis. Therefore, the understanding of the processes from source to sink in the continental margins of China would be enhanced.

长江入海沉积物是南黄海的重要物源。南黄海中部长江物源的识别及其输运机制的查明，对深入了解中国大陆边缘沉积物扩散系统和海陆相互作用特点，都具有重要的科学意义。本研究拟通过南黄海中部6个沉积物岩芯沉积速率的测定，选择近百年来沉积层位中的样品，进行矿物和元素的测试及综合分析，查明沉积物矿物和元素组成及其物质来源；通过南黄海夏季和冬季悬浮体中矿物和元素的测试及综合分析，识别不同季节悬浮体的物质来源，来追踪沉积过程中长江物质的分布和迁移。综合上述研究，识别近百年来南黄海中部长江物质的分布特征，揭示不同季节环流系统影响下长江入海沉积物在南黄海的分布和输运，并结合水团分析对其输运机制做出合理解释，从而提高对中国大陆边缘从源到汇变化过程的认识。

作为一典型的半封闭陆架海，黄海在全新世期间接受了来自黄河与长江的大量入海沉积物。但是，长江入海沉积物对黄海沉积环境的影响及其输运机制还未完全阐明。本研究通过南黄海中部沉积物岩芯粘土矿物、碎屑矿物和化学元素的分析，判别了近百年来沉积物的物质来源；通过表层沉积物粒度、粘土矿物和化学元素的分析，识别了沉积物的物源，并结合海水盐度和悬浮体数据，阐明了长江入海沉积物在南黄海的输运机制。研究结果表明，南黄海表层沉积物主要来自黄河（现代黄河与老黄河水下三角洲）与长江，近百年来南黄海中部沉积物主要来源于黄河。长江沉积物进入南黄海的方式具有季节性差异。夏季，长江沉积物可以通过长江冲淡水的扩散输运至南黄海中部，也可以被苏北沿岸流携带输运至江苏沿海地区；冬季，在苏北沿岸流、黄海沿岸流和黄海暖流的共同作用下，夏季沉积在江苏沿海的长江沉积物可以被输运至南黄海中部甚至更北部。在整个输运过程中，苏北沿海作为长江沉积物的源和汇发生了转换，夏季是长江沉积物的汇，而在冬季则成为长江沉积物的源。长江沉积物在南黄海的分布与运移和环流系统的季节变化密切相关。本研究对于深入了解中国大陆边缘沉积物扩散系统、海陆相互作用以及从源到汇的变化过程，都具有重要的科学意义。