黄河沉积物环山东半岛陆架的搬运和沉积过程及机制研究

The transport, redistribution, and deposition of river sediment on continental shelves (source-to-sink) is a fundamental, long-standing research subject in marine geology and biogeochemistry. It is becoming a growing focus of a wider science community because of its geological and environmental importance, societal relevance, and global change implications. Huanghe is known for its highest sediment concentration and the second largest annual sediment discharge among world’s large rivers. Huanghe sediment is a major source that dominated sedimentation and stratigraphy across the margin of China seas; its transport and deposition patterns have great impact on seafloor geotechnical/stability properties, coastal evolution, and climate change interpretations. Here we propose a field study, the largest so far in the area, that employs multiple observation platforms (tripods and moorings) for simultaneous, in-situ measurements of sediment dynamics processes within the bottom boundary layer. The main goals of this investigation are 1) to quantify the three key modes of sediment transport: advection, diffusion, and wave-supported gravity flows; 2) to better understand the mechanisms of sediment transport and deposition that formed the apron-shaped deposit surrounding the Shandong Peninsula as well as the two mud patches in Yellow Sea; and 3) to verify and calibrate numerical models that reconstruct the paleo-sedimentary environments of the past century. The outcome of this investigation aims not only to enrich the Source-to-Sink thesis, but also to spur the development and application of field technology in China’s sediment dynamics studies.

河流泥沙入海后的输送和归宿是地质学和生物地球化学的基本问题之一，和人类的生存环境密切相关，一直受到海洋地学界的高度关注。黄河在全球河流中悬沙浓度最高，多年平均入海泥沙量居第二，其大量泥沙入海后的输运和沉积不仅是影响中国东部边缘海沉积格局的主控因素，也是渤黄海海底工程、海岸带变迁、甚至区域气候和环境变化研究的重要内容。本申请拟针对环山东半岛陆架的黄河沉积物输运和沉积过程开展研究，通过一个多学科、多尺度的观测研究计划，利用同步的原位连续观测获取高精度海底边界层沉积动力数据，较全面和系统地揭示环山东半岛陆架沉积物的输运过程，阐述多种动力条件下的输送和沉积机制，建立一套率定沉积物输运和沉积的数值模型参数化方案，结合沉积学和地球化学指标，重建百年以来环山东半岛泥质沉积体的演化过程，并预测其未来趋势。项目研究将丰富大河沉积物在陆架海的源－汇作用理论，推动我国海洋沉积动力过程原位观测的研发和应用。

河流入海泥沙的输送和归宿问题是地质学和海洋学的热点问题之一。作为全球输沙量第二大河，黄河曾向海输送高达11亿吨/年的巨量泥沙，这些泥沙一部分在河口快速沉积形成面积广袤的黄河三角洲，另一部分在海流的作用下向外海输运，对东中国海的地貌演化产生深远影响。本申请对黄河沉积物环山东半岛陆架的搬运和沉积过程与机制开展研究，通过高分辨率低扰动沉积物取样、三脚架和浮标原位观测系统、PAM走航观测、水文泥沙综合调查等，结合实验室测试分析和数值模拟计算等手段，揭示了天气事件、季节和年际等不同时间尺度环山东半岛陆架沉积物输运过程，计算了风浪作用下的剪切应力和波轨流速，探讨了风、浪、陆架波等环境动力因素对沉积物输运的控制作用，量化了悬移质和推移质沉积物输运通量，率定了环山东半岛陆架海泥沙沉降速度和抗剪强度，重建了山东半岛泥质沉积体的演化过程。研究结果将丰富我国陆架海物质输运与沉积归宿问题的研究，为系统认识泥质区与现代动力过程的耦合机制提供科学参考。