山溪性入海河流物源变异及对气候事件的响应

Knowledge of source-to-sink processes along the East Asian continental margin is of profound importance to understand land-ocean interaction and associated sediment transport. Considering rapid transport of weathered material, small mountainous rivers play a vital role in the processes of global climate change and surface material cycle, thus are hotspots of geoscience researches. However, the spatio-temporal heterogeneity in mountainous river sources with the response to climate event is poorly understood. This project is devoted to examining the sediment transport pattern in two mountainous rivers in East Asia – the Mulanxi River in Fujian Province of southeast China mainland, and the Zhuoshuixi River in western Taiwan Island. Using methods including phase and grain size separation, mineralogy, elements and Sr-Nd isotope geochemistry, we aim to decipher the spatio-temporal heterogeneity in geochemical composition of river sediment as mainly controlled by sorting effects. Field campaign of sediment transport under stormy condition is conducted to explore rapid response of geochemical composition of river-borne material and the behavior of trace elements. This project will uncover the change in geochemical composition of river material in marginal seas thus deepening our understanding of global material and biogeochemical cycles.

山溪性中小河流在独特气候和地质地貌条件下，物理剥蚀和风化产物的搬运和堆积都非常迅速，在地表物质循环和全球气候环境变化过程中扮演了重要角色，但关于山溪性河流物源时空变异及其对台风-暴雨-洪水极端事件响应的认识还不透彻。东亚大陆边缘发育有活跃的陆海沉积物源汇体系，是研究陆海相互作用和物质交换的关键区域。本课题选择区域构造差异明显的福建木兰溪和台湾浊水溪两类山溪性河流为研究对象，采用不同相态和不同粒级的矿物、元素和Sr-Nd同位素地球化学等多学科交叉的特色研究方法，刻画不同时空尺度河流入海沉积物地球化学组成分异性及河流的搬运分选控制机制；结合极端气候事件期间的综合观测，对比研究事件性过程影响下河流入海物质地球化学组成的快速响应及关键指标元素的地球化学行为特征，由此揭示陆架边缘海物质源汇过程在全球物质循环和生物地球化学循环中的贡献。

针对该课题主要的科学目标，项目组以“地球关键带（CZO）”理念，选取福建木兰溪和台湾浊水溪河流水体和沉积物为主要研究对象，开展了大量水化学、沉积矿物学、不同化学相态/不同粒级沉积物的元素、Sr-Nd同位素以及稳定Sr同位素地球化学分析，揭示我国东南沿海山溪小河的表生风化和物质输送特征及对天气尺度极端事件的响应，阐明台湾快速剥蚀地区的化学风化类型、沉积物地球化学组成变异特征及主控因素，为深入理解东亚大陆边缘代表性山溪性入海河流的源汇过程在全球物质循环和生物地球化学循环中的贡献提供更多科学依据。依托该项目，发表国内外研究论文8篇，包括SCI论文6篇。