长江口悬沙浓度变化趋势及成因

Variation trend of suspended sediment concentration in Yangtze Estuary

基于1959-2011年长江河口水域实测悬沙浓度数据,对其悬沙浓度分布特征及变化趋势进行研究。结果表明:1流域入海水量无明显增减趋势,年内分配过程为洪季水量减少枯季增加,入海沙量和含沙量无论是洪季、枯季或年均为减小趋势;2河口段徐六泾、南支、南北港及北槽进口悬沙浓度伴随入海泥沙量锐减呈现减小趋势,北支受潮汐影响也呈减小趋势,南槽因水动力增加变化不明显;3受分流比减小、上游来沙锐减及河床粗化等影响,2005-2011年北槽上段和下段平均悬沙浓度较2000-2002年减小约33.25%,中段(CSW)受越堤沙量影响较大,呈现一定增加趋势;4长江口外海滨泥沙的再悬浮作用,有效减缓该区域悬沙浓度减小幅度,但仍不能改变其伴随流域入海泥沙锐减的减小趋势,2003-2011年平均悬沙浓度较1981-2002年减小约21.42%;其峰值向口内上溯约1/6经度,且峰值移动主要由径流和潮流水动力对比决定。

Based on the suspended sediment concentration （SSC） observed in Yangtze Estuary in 1959 - 2011, variation trend and characteristics of suspended sediment concentration distribution is analyzed. The an- nual total seaward flow discharge volume didn＇t change, but decreased in flood season and increased in dry season. Secondly, seaward sediment volume decreased in both flood and dry season. In the estuary, suspen- ded sediment concentration decreased except for that of South Passage. Thirdly, suspended sediment concen- tration in North Passage reduced 33.25% because of the decrease of separate ratio and sediment from upstream and the coarsening of bed material. But that in middle North Passage increased as the result of sediment pass- ing over the bar. Finally, re-suspended sediment in the outside sea slowed down the decrease range of suspen- ded sediment concentration, but not changed the decrease trend of sediment. Suspended sediment concentration decreased 21.42% from 2003 - 2011 to 1981 - 2002. The peak point moves upstream 1/6 longitude which is decided by the ratio of runoff and tidal hydrodynamics.