| LI Zhanhai,LI Michael Z,DAI Zhijun,ZHAO Fangfang,LI Jiufa. 2015. Intratidal and neap-spring variations of suspended sediment concentrations and sediment transport processes in the North Branch of the Changjiang Estuary. Acta Oceanologica Sinica, 34(1):137－147 |
| Intratidal and neap-spring variations of suspended sediment concentrations and sediment transport processes in the North Branch of the Changjiang Estuary |
| 长江口北支悬沙浓度在潮周期内和大小潮周期尺度的变化特征及输运研究 |
| Received:November 18, 2013 Revised:June 04, 2014 |
| DOI：10.1007/s13131-015-0605-z |
| Key words:suspended sediment concentration intratidal and neap-spring variation impact of water exchange resuspension settling Changjiang (Yangtze River) Estuary |
| 中文关键词: 悬沙浓度 潮周期内和大小潮周期变化 水交换效应 再悬浮 沉降 长江口 |
| 基金项目:The National Science Foundation of China under contract Nos 50939003 and 41176069; the Foundation of State Key Laboratory of Estuarine and Coastal Research, East China Normal University of China under contract No. SKLEC-2012KYYW06. |
| Author Name | Affiliation | E-mail | | LI Zhanhai | State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China | zhli@sklec.ecnu.edu.cn | | LI Michael Z | Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, dartmouth, B2Y 4A2, Canada | | | DAI Zhijun | State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China | | | ZHAO Fangfang | State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China | | | LI Jiufa | State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China | |
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| Abstract: |
| Profiles of tidal current and suspended sediment concentration (SSC) were measured in the North Branch of the Changjiang Estuary from neap tide to spring tide in April 2010. The measurement data were analyzed to determine the characteristics of intratidal and neap-spring variations of SSC and suspended sediment transport. Modulated by tidal range and current speed, the tidal mean SSC increased from 0.5 kg/m3 in neap tide to 3.5 kg/m3 in spring tide. The intratidal variation of the depth-mean SSC can be summarized into three types: V-shape variation in neap tide, M-shape and mixed M-V shape variation in medium and spring tides. The occurrence of these variation types is controlled by the relative intensity and interaction of resuspension, settling and impact of water exchange from the rise and fall of tide. In neap tide the V-shape variation is mainly due to the dominant effect of the water exchange from the rise and fall of tide. during medium and spring tides, resuspension and settling processes become dominant. The interactions of these processes, together with the sustained high ebb current and shorter duration of low-tide slack, are responsible for the M-shape and M-V shape SSC variation. Weakly consolidated mud and high current speed cause significant resuspension and remarkable flood and ebb SSC peaks. Settling occurs at the slack water periods to cause SSC troughs and formation of a thin fluff layer on the bed. Fluxes of water and suspended sediment averaged over the neap-spring cycle are all seawards, but the magnitude and direction of tidal net sediment flux is highly variable. |
| 中文摘要: |
| 2010年4月在长江口北支开展了由小潮至大潮的连续流速和悬沙浓度剖面观测, 利用该观测资料对悬沙浓度的时间变化特点和输运特征进行了研究. 结果表明, 在潮差和流速的驱动下, 悬沙浓度具有明显的大小潮变化, 潮周期平均浓度由小潮的0.5 kg/m3增加到大潮的3.5kg/m3. 悬沙浓度在潮周期内的时间变化过程可概括为3种类型: 小潮时期的V型变化, 中大潮时期的M型和M-V混合型变化. 这些变化类型的产生主要与再悬浮、沉降和由潮位变化引起的水体交换有关. 在小潮期间北槽与口外海域的水体交换效应是导致V型变化的主要因素. 而在中大潮期间, 再悬浮和沉降作用变得非常重要, 它们与落潮持续较长的高流速和短暂的落憩历时共同主导了M型和M-V型的产生. 中大潮期间的强流速和底床上的弱固结性泥沙使再悬浮发生显著, 并导致了涨落潮阶段明显悬沙浓度峰的出现. 沉降作用发生在各潮周期的憩流时段, 它使水体中的浓度明显降低并在底床上形成浮泥状的新沉积物. 在一个大小潮周期尺度上, 北槽的水通量和悬沙通量向海, 但潮周期平均的悬沙通量在强度和方向上存在较大的变化性. |
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