伶仃洋河口泥沙絮凝特征及影响因素研究

田枫; 欧素英; 杨昊; 刘锋

伶仃洋河口泥沙絮凝特征及影响因素研究

中山大学海洋科学学院河口海岸研究所, 广东广州 510006

基金项目: 国家自然科学基金项目（41106015，41476073）；科技部科技基础性工作专项重点项目“中国典型河口动力沉积地貌本底数据调查”（2013FY112000）。

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出版历程
- 收稿日期: 2016-06-18

Study on the flocs characteristic and dynamics effects in the Lingdingyang Estuary

Institute of Estuarine and Coastal Research, School of Marine Sciences, Sun Yat-Sen University, Guangzhou 510006, China

摘要

摘要: 泥沙絮凝对河口细颗粒泥沙运动过程起着极其重要的作用。本文通过LISST-100激光粒度仪等仪器实测伶仃洋河口2013年洪季悬浮泥沙絮凝体现场粒径及水动力、泥沙条件，结合实验室悬沙粒径分析，研究大小潮期间伶仃洋河口泥沙絮凝特征，探讨紊动剪切强度、含沙量、盐度分层及波浪等因素对伶仃洋河口泥沙絮凝的影响。结果表明：伶仃洋河口水体中现场粒径平均值为148.53 μm，大于实验室悬沙分散粒径36.74 μm，河口絮凝现象明显；沉速与有效密度、粒径呈正相关，絮团平均有效密度为153.49 kg/m³，平均沉速达1.13 mm/s；小潮时絮团平均粒径大于大潮，垂向上表底层絮团粒径小、中层大，中底层絮团沉速大于表层。伶仃洋河口水动力、泥沙条件是影响其泥沙絮凝的重要因素，低剪切强度（小于5 s^-1）、低含沙量（小于50 mg/L）及高体积浓度有利于细颗粒泥沙之间的相互碰撞，促进絮凝作用；当剪切强度与颗粒间碰撞强度高于絮团所能承受的强度时，絮团易破碎分解成小絮团或更细的泥沙颗粒；伶仃洋河口盐度层化引起的泥沙捕获现象增大中层泥沙体积浓度，有利于中层絮凝体的发育；观测期相对较大的波浪增强水体紊动，增大了水体细颗粒泥沙的碰撞几率，表层絮团粒径随波高峰值的出现而增大。
- 伶仃洋 /
- 泥沙絮凝 /
- 沉速 /
- 盐度层化 /
- 波浪 /
- 紊动剪切强度
Abstract: Flocculation plays an important role at the behavior of fine sediment in estuary. During 22-29 of July, 2013, the suspended sediment concentration, size of floc, tidal current, salinity and wave were observed in Lingdingyang Estuary by LISST-100 together with other instruments. Based on these situ data and laboratory analysis of dispersed suspended sediment, the characteristics of sediment flocculation and the influences of dynamic factors on flocculation were studied. The results show that there were obvious flocculation at observed filed of Lingdingyang Estuary, which the mean situ floc size is 148.53 μm, larger than the mean size of laboratory dispersed sediment particles (36.74 μm). The settling velocity was positively correlated with effective density and floc size, while the effective density of floc in Lingdingyang Estuary was about 153.49 kg/m³, and the average settling velocity reached 1.13 mm/s; floc size in flood and neap tide was larger than ebb and spring tide, the flocculation in middle water column was greater than upper water and bottom water. The effects of turbulent shear, suspended sediment concentration, salinity stratification and wave on flocculation in Lingdingyang Estuary were considered. The in situ data shows that under low turbulent shear (<5 s^-1), low suspended sediment concentration (<50 mg/L) and high volume concentration, promoted the flocculation, and floc would break-up when strength of turbulent shear and particles collision were greater than strength floc can withstand. Salinity stratification result in volume concentration increased rapidly in the middle water column due to sediment trapping, which promote flocculation. The increase of short wind wave also help the flocculation at upper water during in observation period.
- Lingdingyang Estuary /
- flocculation /
- settling velocity /
- salinity stratification /
- waves /
- turbulent shear strength

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