东海陆源物质跨陆架输运的沉积响应及其机制研究

Cross-shelf transport of terrestrial materials plays an important role in the delivery of river sediments to the oceans and the removal of pollutants in the coastal areas. It is also a significant part of the study on the interaction between land and ocean, the process of source to sink, and the research of modern sedimentology. Previous studies have shown that there has an obvious material cross-shelf transport near the Zhejiang coast, and the nearshore materials can be transported to the middle-outer shelf. However，little research has been done on the impact of cross-shelf transport on the sediments distribution pattern in the East China Sea continental shelf and the mechanism of material cross-shelf transport is still indistinct. Our project intends to investigate the sedimentary response and its’ seasonal and long-term variations of terrigenous matter cross-shelf transport in the East China Sea continental shelf and discuss the mechanism based on sediment grain size, mineral contents and elements concentration distributions of surficial sediments, suspended sediments and sediment cores. The sediment transport trend and the control mechanism of cross-shelf transport will be explained combines with water mass analyze and the role of Kuroshio intrusion in the sediment cross-shelf transport will be discussed. The results of this study are of great significance to the correct understanding of the modern depositional processes and the formation of sedimentary patterns on the East China Sea shelf and will also provide new ideas for the study of the global "source to sink" process.

陆源物质跨陆架输运在河流泥沙向外海输送及沿岸污染物清除等过程中起到重要作用，同时也是陆海相互作用和源汇过程研究的重要内容，在现代沉积学研究中占有重要地位。研究表明浙江沿岸附近，物质存在明显的跨陆架横向输运，近岸物质可输运至中外陆架。但跨陆架输运对东海陆架沉积物分布格局的影响少有研究涉及，且跨陆架输运的机制仍未明确。因此本项目拟利用多年夏、冬季节采集的东海陆架表层沉积物、悬浮体沉积物样品结合典型区域的岩芯样品进行粒度、矿物和地球化学元素分析，查明跨陆架输运对东海陆架沉积物分布格局的影响及其季节、长期变化，并结合温盐等观测数据进一步判断沉积物输运趋势，分析跨陆架输运的控制机制，探讨黑潮入侵在沉积物跨陆架输运中所起的作用。研究结果对正确认识东海陆架现代沉积过程及沉积格局的形成具有重要意义，也将为海陆相互作用和源汇过程的研究提供新的思路。

东海陆架位于亚洲大陆与西太平洋之间，是二者进行物质能量交换的重要通道。前人观测发现，东海陆架物质可跨越海流切变锋向中外陆架输送，但东海陆源物质跨陆架输运的沉积响应尚未明确，其机制也有待查明。本项目利用东海陆架获取的水文数据、悬浮体、沉积物样品查明了跨陆架输运对东海陆架沉积物分布格局的影响并探讨黑潮入侵在沉积物跨陆架输运中所起的作用。首先，根据四个年份春、秋季取得的表层沉积物粒度、碎屑矿物分布发现，29°N附近存在明显的细粒沉积物跨陆架输运，细粒沉积物可向东输运至124°40'E，甚至更远的区域。跨陆架输运位置相对固定，但方向、范围存在明显的季节性、年际变化，表明陆源物质跨陆架输运并不是偶然现象且已对东海陆架沉积格局产生了影响。此外，跨陆架输运发生位置的南部存在一明显缺乏现代细粒沉积物的区域，这一区域与黑潮入侵分支位置一致。同时结合水文及悬浮体数据发现黑潮分支入侵内陆架是引起沉积物跨陆架输运的重要因素之一，其强度的季节及年际变化影响了东海陆架沉积物跨陆架输运的方向及范围，黑潮入分支入侵对东海内陆架泥质沉积的形成尤其是两个沉积中心的形成起到至关重要的作用。其次，我们对SS4、SS10孔沉积物进行碎屑矿物、黏土矿物及Sr-Nd同位素分析，结果表明1.5 kyr BP以来东海内陆架泥质沉积区沉积物主要来源于长江，同时受到闽浙沿岸小型河流的影响，在气候及人类活动影响下730 yr BP以来长江沉积物对东海内陆架泥质沉积的贡献相对增加，沿岸小河流沉积物贡献相对减少。综上，通过该项目的研究，使得我们对东海陆架源-汇过程及陆架沉积格的局形成有了更全面的认知，为海陆相互作用研究提供了新的思路。