Field measurement and modeling of near-bed sediment transport processes with fluid mud layer in Tokyo Bay
Field measurement and modeling of near-bed sediment transport processes with fluid mud layer in Tokyo Bay
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DOI：
10.1007/s10236-012-0570-4
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发表时间：
2012-09
期刊：
影响因子：
2.3
通讯作者：
Y. Nakagawa;K. Nadaoka;H. Yagi;Ryuichi Ariji;H. Yoneyama;K. Shirai
中科院分区：
文献类型：
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作者：
Y. Nakagawa;K. Nadaoka;H. Yagi;Ryuichi Ariji;H. Yoneyama;K. Shirai
东京湾是日本的河口之一，流域内人口近2600万。该水域环境的主要问题之一是生态系统功能的下降，包括各种人类活动造成的水和沉积物质量的恶化。由于内湾几乎整个区域的底部沉积物均由有机物含量高的细小物质组成，这些物质会通过缺氧等过程导致水质恶化，因此了解海湾内细小沉积物的动态对于水域的环境评估至关重要。本文提出了精细沉积物动力学关键过程的模型，该模型反映了2007年监测中获得的泥床结构及其动力学的现场数据。目前海湾沉积物的一个特点是持续存在厚度约几分米的流体泥层（含水量超过300%），这可能是由于富营养化导致大量有机颗粒沉积所致。本研究表明，在根据声多普勒测速仪系统测量的垂直通量的时间序列数据校准模型参数后，扩散通量模型为估计流体泥浆层顶部的侵蚀通量提供了相当可靠的结果。本研究还基于宾汉流体概念，推导出施加外部剪应力力的流体泥浆层中平流通量的解析解。
Tokyo Bay is one of the estuaries in Japan with a high population of almost 26 million people in the basin area. One of the major concerns for the environment in this water area is the decreasing ecosystem functions including the deterioration of water and sediment qualities caused by various anthropogenic activities. Since the bottom sediments around almost the entire area of the inner bay consist of fine materials with a high organic content, which cause the deterioration of water quality through processes such as hypoxia, an understanding of the fine sediment dynamics in the Bay is crucial for an environmental assessment of the water area. This paper proposes a model for the key processes of fine sediment dynamics, which reflects field data about muddy bed structures and their dynamics obtained during the monitoring campaign in 2007. One of the specific features of the sediment in the Bay at present is the persistent existence of fluid mud layers (water content over 300 %) with a thickness of around a few decimeters, which might be caused by deposition of abundant organic particles due to eutrophication. The present study shows that diffusion flux model delivers quite reliable results for estimating erosion flux from the top of fluid mud layers after calibrating the model parameter against the time series data of vertical flux measured by an acoustic Doppler velocimeter system. This study also derives analytical solutions, based on the Bingham fluid concept, of advection flux in the fluid mud layer on which external shear stress force is applied.