长江口外低氧区近千年来的沉积地球化学过程演变及其生态环境效应

This study featurs the modern process-geological record integration, and selects the Changjiang Estuary delta to the near sea area for laying representative fixed stations, and collecting a number of high-quality shallow seismic profiles and sedimentary cores. Based on the multi-disciplinary analysis of dating, sediment grain size, elements, microfossils and isotopes of their shells, and biomarkers, in combination with the new technology of U isotope analysis, this study will systematically reconstruct the changes in depositional, marine (temperature, salinity) and ecological (paleo-productivity, hypoxia) environments at centennial to decadal timescales in the studied area over the last one thousand year, and hence to establish the high-resolution sequences of the evolution of sedimentary geochemical and biogeochemical processes. On this basis, compared with the field and historical observations, this study will explore the sedimentary and ecological environmental factors controlling the evolution of the hyposia area off the Changjiang Estuary; compared with the records of monsoonal precipitation on surrouding land and polar ice core to reveal the global and regional abrupt events; meanwhile, compared with the data of human activities in the studied area to differentiate the natural factors of land-sea interaction and human influence. This study will provide a scientific basis for understanding the the regional responses of the Changjiang River Delta to global change and protecting the ecological environment of the Changjiang Estuary.

本项研究以现代过程与地质记录相结合为特色，选择长江口外水下三角洲至临近海区，布设具代表性的固定研究站位，同时采集一批高质量的浅地层剖面和若干沉积岩芯，开展测年、沉积物粒度、元素、微体古生物及壳体同位素、生物标记物等多学科分析,结合U同位素分析等新技术，系统提取研究区近千年来在百年至年代际尺度上沉积环境、海洋环境（温度、盐度）和生态环境（古生产力、缺氧层）变化的特征，建立高分辨率的沉积地球化学和生物地球化学过程的演变序列。在此基础上，与现场和历史观测资料进行对比，探讨控制长江口外低氧区和缺氧现象演变的沉积和生态环境因素；与周围陆地季风和极地冰芯记录进行对比，揭示出全球性和区域性的突然事件；同时，与研究区的人类活动资料进行对比，甄别陆海相互作用中的自然因素和人类活动引起的叠加效应，为理解长江三角洲地区对全球变化的区域响应和长江口区生态环境的保护提供科学依据。

本项研究以现代过程与地质记录相结合为特色，选择长江口外水下三角洲至临近海区，布设具代表性的固定研究站位，同时采集一批高质量的浅地层剖面和若干沉积岩芯，开展测年、沉积物粒度、元素、微体古生物及壳体同位素、生物标记物等多学科分析，结合U同位素分析等新技术，系统提取研究区近千年来在百年至年代际尺度上沉积环境、海洋环境（温度、盐度）和生态环境（古生产力、缺氧层）变化的特征，建立高分辨率的沉积地球化学和生物地球化学过程的演变序列。在此基础上，与现场和历史观测资料进行对比，探讨控制长江口外低氧区和缺氧现象演变的沉积和生态环境因素；同时，与研究区的人类活动资料进行对比，甄别陆海相互作用中的自然因素和人类活动引起的叠加效应，为理解长江三角洲地区对全球变化的区域响应和长江口区生态环境的保护提供科学依据。