夏季长江口外缺氧频发的机制及酸化问题初探
发布时间：2018-11-10 12:28
【摘要】：针对夏季长江口外缺氧区,深入认识了同缺氧发生有着密切联系的特殊海底地形、流场环境、锋面和上升流等主要环境特征;特别地,夏季长江口外羽状锋和上升流这两种物理过程是耦合在一起的,羽状锋的垂向分布形态与上升流具有密切的联系.基于对夏季长江口外历史缺氧事件的回顾与分析,从统计学意义上展现了缺氧区在水平分布上的空间结构,并认识了缺氧发生区位置的细节,发现口门外内陆架区的溶解氧(DO)含量与水深之间呈"V"型关系,据此指出内陆架的缺氧水体多发生在具有陡峭海底地形的坡面上.在长江口外缺氧机制现有认知的基础上,剖析了口门外陡坡地形何以能成为夏季缺氧核心频发区的生物地球化学机制,阐释了坡面处缺氧区位置与羽状锋面和上升流的内在联系.长江口外羽状锋和上升流及其耦合作用是诱发夏季缺氧的重要驱动力,长江冲淡水羽状锋扩展和上升流交互作用影响下营养盐的持续输送和该处良好的光照条件是夏季长江口外浮游植物繁殖和底层缺氧的重要机制.通过对缺氧区耗氧作用及有机碳矿化和营养盐再生的探讨,指出夏季长江口外显著的耗氧过程亦主要发生在具有锋面和上升流特征的陡峭坡面附近,并证实底层缺氧区存在营养盐的表观丢失现象;同时,分析显示长江口外泥质区底边界层中的沉积物再悬浮也可对有机碳耗氧矿化及营养盐循环与再生产生影响.研究还指出长江口外的陡坡地形也是夏季低pH酸化环境的主要发生区,陡坡处羽状锋面和上升流的耦合亦为诱发夏季底层酸化的重要物理驱动力.最后,对今后长江口外缺氧区和水体酸化研究中予以关注的问题进行了探讨.
[Abstract]:In view of the anoxic zone outside the Changjiang Estuary in summer, the main environmental characteristics of the sea floor topography, flow field, front and upwelling which are closely related to the occurrence of hypoxia are deeply understood. In particular, the two physical processes, the plume front and upwelling, are coupled together in summer, and the vertical distribution of the plume front is closely related to the upwelling. Based on the review and analysis of the historical anoxia events outside the Changjiang Estuary in summer, the spatial structure of the horizontal distribution of the anoxic region is shown statistically, and the location of the anoxic region is recognized in detail. It is found that there is a "V" type relationship between dissolved oxygen (DO) content and water depth in the continental shelf area outside the mouth, and it is pointed out that the anoxic water body of the inland shelf mostly occurs on the slope with steep submarine topography. Based on the existing cognition of the mechanism of hypoxia outside the Changjiang Estuary, this paper analyzes the biogeochemical mechanism why the steep slope topography at the entrance of the Changjiang Estuary can become the core area of hypoxia in summer. The relationship between the position of anoxic zone on the slope and the pinnate front and upwelling is explained. The external plume front and upwelling in the Changjiang Estuary and their coupling are the important driving forces to induce anoxia in summer. The continuous transport of nutrients and good illumination conditions are the important mechanisms of phytoplankton propagation and hypoxia in the bottom layer of Yangtze River Estuary in summer under the influence of plume expansion and upwelling of Yangtze River Estuary. Based on the discussion of oxygen consumption, organic carbon mineralization and nutrient regeneration in the anoxic region, it is pointed out that the significant process of oxygen consumption outside the Changjiang Estuary in summer also mainly occurs near the steep slope with the characteristics of frontal and upwelling. The apparent loss of nutrients in the anoxic zone of the bottom layer was confirmed. At the same time, the analysis shows that the sediment resuspension in the bottom boundary layer of the outer muddy area of the Yangtze River Estuary can also affect the organic carbon oxygen consumption mineralization, nutrient cycling and regeneration. It is also pointed out that the topography of steep slope outside the Changjiang Estuary is also the main occurrence area of low pH acidification environment in summer, and the coupling between the plume front and upwelling at the steep slope is also an important physical driving force to induce the bottom acidification in summer. Finally, the problems concerned in the study of anoxic zone and water acidification outside the Changjiang Estuary are discussed.
【作者单位】： 中国海洋大学海洋化学理论与工程技术教育部重点实验室;国家海洋局第一海洋研究所;青岛海洋科学与技术国家实验室海洋生态与环境科学功能实验室;国家海洋局第二海洋研究所海洋生态系统和生物地球化学重点实验室;
【基金】：国家自然科学基金项目(批准号:41206068,41620104001) 国家自然科学基金委-山东省联合基金项目(批准号:U1406403) 中央级公益性科研院所基本科研业务费专项资金(编号:2016G08) 青岛海洋科学与技术国家实验室海洋生态与环境科学功能实验室开放基金(编号:KLMEES201603) 国家重点基础研究发展计划项目(编号:2010CB428703) 中国近海海洋综合调查与评价专项(编号:908-ZC-I-03)资助
【分类号】：P734
本文编号：2322474
[Abstract]:In view of the anoxic zone outside the Changjiang Estuary in summer, the main environmental characteristics of the sea floor topography, flow field, front and upwelling which are closely related to the occurrence of hypoxia are deeply understood. In particular, the two physical processes, the plume front and upwelling, are coupled together in summer, and the vertical distribution of the plume front is closely related to the upwelling. Based on the review and analysis of the historical anoxia events outside the Changjiang Estuary in summer, the spatial structure of the horizontal distribution of the anoxic region is shown statistically, and the location of the anoxic region is recognized in detail. It is found that there is a "V" type relationship between dissolved oxygen (DO) content and water depth in the continental shelf area outside the mouth, and it is pointed out that the anoxic water body of the inland shelf mostly occurs on the slope with steep submarine topography. Based on the existing cognition of the mechanism of hypoxia outside the Changjiang Estuary, this paper analyzes the biogeochemical mechanism why the steep slope topography at the entrance of the Changjiang Estuary can become the core area of hypoxia in summer. The relationship between the position of anoxic zone on the slope and the pinnate front and upwelling is explained. The external plume front and upwelling in the Changjiang Estuary and their coupling are the important driving forces to induce anoxia in summer. The continuous transport of nutrients and good illumination conditions are the important mechanisms of phytoplankton propagation and hypoxia in the bottom layer of Yangtze River Estuary in summer under the influence of plume expansion and upwelling of Yangtze River Estuary. Based on the discussion of oxygen consumption, organic carbon mineralization and nutrient regeneration in the anoxic region, it is pointed out that the significant process of oxygen consumption outside the Changjiang Estuary in summer also mainly occurs near the steep slope with the characteristics of frontal and upwelling. The apparent loss of nutrients in the anoxic zone of the bottom layer was confirmed. At the same time, the analysis shows that the sediment resuspension in the bottom boundary layer of the outer muddy area of the Yangtze River Estuary can also affect the organic carbon oxygen consumption mineralization, nutrient cycling and regeneration. It is also pointed out that the topography of steep slope outside the Changjiang Estuary is also the main occurrence area of low pH acidification environment in summer, and the coupling between the plume front and upwelling at the steep slope is also an important physical driving force to induce the bottom acidification in summer. Finally, the problems concerned in the study of anoxic zone and water acidification outside the Changjiang Estuary are discussed.
【作者单位】： 中国海洋大学海洋化学理论与工程技术教育部重点实验室;国家海洋局第一海洋研究所;青岛海洋科学与技术国家实验室海洋生态与环境科学功能实验室;国家海洋局第二海洋研究所海洋生态系统和生物地球化学重点实验室;
【基金】：国家自然科学基金项目(批准号:41206068,41620104001) 国家自然科学基金委-山东省联合基金项目(批准号:U1406403) 中央级公益性科研院所基本科研业务费专项资金(编号:2016G08) 青岛海洋科学与技术国家实验室海洋生态与环境科学功能实验室开放基金(编号:KLMEES201603) 国家重点基础研究发展计划项目(编号:2010CB428703) 中国近海海洋综合调查与评价专项(编号:908-ZC-I-03)资助
【分类号】：P734
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