| 河控型河口盐度层化对悬沙的捕集机制 |
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| 引用本文： | 谢荣耀,刘锋,罗向欣,牛丽霞,蔡华阳,杨清书.河控型河口盐度层化对悬沙的捕集机制[J].海洋学报,2021,43(5):38-49. |
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| 作者姓名： | 谢荣耀 刘锋 罗向欣 牛丽霞 蔡华阳 杨清书 |
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| 作者单位： | 1.中山大学 海洋科学学院，广东 珠海 519082 |
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| 基金项目： | 国家自然科学基金（41706088，51979296）；广东省自然科学基金(2017A030310435)；国家重点研发计划项目（2016YFC0402600）；广东省水利科技创新项目（2016-21，2016-20），中山大学高校基本科研业务费青年教师培育项目（18lgpy29） |
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| 摘 要： | 河控型河口盐度混合和层化是控制悬沙输移扩散的重要动力机制。以珠江磨刀门河口为研究对象，基于2017年洪季三船同步大、小潮水文泥沙观测数据，分析河控型河口水体盐度层化结构的时空变化对悬沙分布的影响机制。结果表明:受径潮动力耦合时空变化影响，河口盐度垂向分布表现出时空差异，即受径流主导的M1站(挂锭角)，河口盐度在涨落潮周期内垂向混合均匀，受径潮控制的M2站(口门)在整个潮周期内盐度层化结构明显，口门外侧的M3站，潮动力作用较强，盐度垂向分布随涨落潮变化而变化；悬沙空间分布与盐度分布关系密切，盐度混合均匀利于悬沙垂向均匀分布，而盐度层化则使悬沙倾向于滞留在底层水体中，且在盐度层结界面之下出现高悬沙浓度，悬沙浓度垂向分布曲线呈L字型或抛线型，纵向上表现为高浓度悬沙团抑制在盐水楔前端，盐度层化对悬沙的捕集效应明显。通过对比水体标准化分层系数与水流垂向扩散强度系数发现，两者呈现负相关关系，即标准化分层系数愈大，垂向扩散强度愈小，表明水体层化抑制悬沙垂向扩散强度，而且水体层化程度越高，悬沙垂向扩散抑制程度越大，进而促进了河口水体盐度层化对悬沙捕集作用。本研究有助于揭示河口细颗粒泥沙运动机制及河口拦门沙演变机制，并为磨刀门河口拦门沙治理提供科学依据。
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| 关 键 词： | 悬沙分布 盐度层化 泥沙捕集 磨刀门河口 河控河口 |
| 收稿时间： | 2020-03-03 |
Sediment trapping mechanism by salinity stratification in a river-dominted estuary: A case study of the Modaomen Estuary in flood season |
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| Institution: | 1.School of Marine Science, Sun Yat-Sen University, Zhuhai 519082, China2.Institute of Estuarine and Coastal Research, School of Marine Engineering and Technology, Sun Yat-Sen University, Zhuhai 519082, China3.Guangdong Provincial Engineering Research Center of Coasts, Islands and Reefs, Guangzhou 510275, China4.State and Local Joint Engineering Laboratory of Estuarine Hydraulic Technology, Guangzhou 510275, China |
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| Abstract: | Salinity mixing and stratification in the river-dominated estuaries are important dynamic mechanisms for controlling transport and diffusion of suspended sediment. Based on the synchronous field investigation with three surveying vessels in the flood season in 2017, covering the spring and neap tidal cycles, the influence mechanism of salinity stratification on suspended sediment distribution in the Modaomen Estuary was analyzed in this study. Vertical distribution of salinity in the estuary also displayed spatial differences under the influence of interaction between riverine and tidal dynamics. The salinity at M1 Station (Guading Jiao), dominated by runoff, was mixed well vertically over the tidal cycles; salinity stratification occurred at the M2 Station (outlet location) and at M3 Station (outside the mouth), which were influenced by interaction between runoff and tide over the tidal cycles. Spatial distribution of suspended sediment was closely related to spatial distribution of salinity. In general, salinity mixing promoted the vertical mixing of suspended sediment, while salinity stratification constrained the suspended sediment to be concentrated in the bottom water layer, and high suspended sediment concentration (SSC) tended to appear at the layer where salinity stratified occur. The vertical distribution curve of SSC was L-shape or paracurve shape, while high SSC always concentrated in the front of the salinity wedge in the longitudinal direction, indicating a significant sediment trapping effect caused by salinity stratification. Comparing the stratification ratio and vertical diffusion coefficient at three gauging stations, there was a negative relationship between them, the larger stratification ratio is, the smaller vertical diffusion coefficient is, indicating the suppression effect of stratification on vertical diffusion. Furthermore, the higher stratification is, the larger suppression effect is. Such mechanism contributes to the sediment trapping caused by stratification. This study is helpful to reveal the mechanism of fine sediment movement and the mechanism of evolution of mouth bar in a complicated estuary, and provide scientific basis for regulation of mouth bar in the Modaomen Estuary. |
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