Sediment dynamics of turbidity maximum in Changjiang River mouth in dry season
Sediment dynamics of turbidity maximum in Changjiang River mouth in dry season
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DOI：
10.1007/s11707-008-0043-8
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发表时间：
2008-06
期刊：
影响因子：
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通讯作者：
J. Gao;Yang Yang-Yang;Ya Wang;S. Pan;Rui Zhang
中科院分区：
文献类型：
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作者：
J. Gao;Yang Yang-Yang;Ya Wang;S. Pan;Rui Zhang
2003年11月16日，利用声学多普勒流速剖面仪（ADCP）在长江口南港两个锚站和一个断面上采集了中、小潮期间的高分辨率流速和悬沙浓度资料。此外，在大潮期间，用传统方法在两个站进行了潮汐周期（13小时）观测。结果表明，再悬浮不仅发生在涨、落潮的最大值，而且在中小潮的落潮初期也有发生。当潮流由高潮向落潮过渡时，流速加快。随后，具有低临界阈值的细粒沉积物被重新悬浮并增加浓度。观测季节河口区在中、小潮相仍处于淤积状态，计算的再悬浮通量在10 - 4-10 - 7 kg·m-2/s数量级。南港的悬浮泥沙输运主要受淡水流量的影响，但由潮汐振荡引起的Storks漂流、垂向环流和垂向剪切作用也对悬浮泥沙的输运起着重要作用。大潮期的再悬浮泥沙通量大于中、小潮期，特别是在最大落潮和最大涨潮时。研究表明，冬季强再悬浮与较大流速相对应。此外，“潮汐抽水”效应和潮汐重力环流也是长江口最大浑浊带形成的重要原因。
High-resolution current velocity and suspended sediment concentration (SSC) data were collected by using an Acoustic Doppler Current Profiler (ADCP) at two anchor stations and a cross-section in the South Channel of the Changjiang River mouth during meso and neap tides on Nov. 16, 2003. In addition, tidal cycle (13-hour) observation at two stations was carried out with traditional methods during the spring tide. Results indicated that resuspension occurred not only at the flood and ebb maximum, but also in the early phase of ebb in the meso and neap tide. When tidal current transited from high to ebb phase, current speed accelerated. Subsequently, fine-grained sediment with low critical threshold was resuspended and increased concentration. The river mouth area remained in siltation in the meso and neap tidal phase during the observation season, with calculated resuspension flux in the order of magnitude of 10−4–10−7kg·m−2/s. Suspended sediment transport in the South Channel was dominated by freshwater discharge, but the Storks drift, vertical circulation and vertical shear effect due to tidal oscillation also played an important role in resuspension and associated sediment transport. In contrast, resuspension sediment flux in the spring tide was larger than that in meso and neap tide, especially at the ebb maximum and flood maximum. The present study revealed that intensive resuspension corresponded well with the larger current velocity during winter. In addition, the ‘tidal pumping’ effect and tidal gravity circulation were also vital for forming the turbidity maximum in the Changjiang River estuary.