【作者】 蒋东辉；

【导师】 高抒；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2002， 博士

【摘要】 分隔并连接两个海域水体的海峡是各种物质进行输运和交换的通道(诸如沉积物、营养化学物质、污染物质及微体古生物长距离的搬运)，因而广受关注，其中的沉积物交换是海洋地质学的一个重要理论和应用课题。海峡地区由于地形和水动力条件多变，沉积物分布的空间梯度大，有利于揭示不同搬运机制的作用和影响以及评价区域性和局部性的影响。作为渤海和北黄海物质交换和输运通道的渤海海峡也不例外，其独特的地质和水文条件为沉积物搬运的研究提供了极好的研究区域。 本文根据渤海海峡空间尺度的大小、潮流特征和沉积物的性质特征，构造了一个垂向二维沉积物输运数值模型，结合已经取得的有关潮流和沉积物的各种相关资料，进行了沉积物长期输运的数值摸拟，所得结果符合实测的结果，揭示了本区沉积物长期输运和沉积的分布格局。 根据Van Karman-prandtl方程导出了将U转化成U100的公式。经4个ADCP站位的流速实测值的验证，该转化公式适用于渤海海峡区。从基本的物理概念和物质守恒定律导出了海底沉积物通量的计算表达式，应用该式取得了与实际海域相符的海底冲淤分布图。用海底泥沙通量代替散度来表征海底的冲淤，物理概念明确。 潮汐潮流的模拟计算结果与沿岸42个潮汐测站的实测值结果对比达到了精度的要求，同时，计算得到的各分潮同潮图与实测结果相符。这些结果表明模型对潮汐潮流的模拟是正确的。 各分潮欧拉余流总的分布趋势表明北黄海中部泥区细颗粒沉积物输运的量值很小，K1和S2分潮欧拉余流各自在山东半岛北侧近岸泥质区形成的顺时针涡漩可能促进了该处的泥质沉积。然而余流的趋势虽有可能反映细颗粒沉积物输运的最大概率方向，却难以与粗颗粒沉积物的输运对应起来。 沉积物长期净输运证实了程鹏(2000)关于沉积物在成山头以北近岸有向东和向东北的净输运趋势的猜测。对应于北黄海中部泥区沉积物净输运图出现为一个反时针的涡漩，表明沉积物的输运取汇聚态势，这也证实了程鹏(2000)有关沉积物向北黄海中部汇聚的结论。在辽东半岛南岸，沉积物净输运图与粒径趋势分析的结果不相符合。粒径趋势分析在冲刷区是不成立的，这由其方法的前提条件所决定。 海底剪切应力的分布与海底沉积物类型的分布的对应关系。中部泥区为应力低值区所在，水动力弱的中部泥区只能接受弱水动力带来的细颗粒物质，而且这些细颗粒物质一旦沉积下来，便难以再悬浮搬运走，说明中部泥区是连续沉积细颗粒物质沉积区。 活动层厚度的分布与海底沉积物类型的分布存在良好的对应关系。北黄海中部泥区活动层为全区最小，在0.13~以下。烟台北部近岸泥区亦对应活动层低值区(其值在0.2~以下)。活动层厚度的大小代表了海底沉积物活动性的强弱，这一分布表明:在泥区沉积下来的细颗粒沉积物，活动性非常弱，又由于该区水动力微弱，沉积物的临界起动值很高，因而难于被再悬浮搬运到他处。 海底冲淤趋势图显示，中部泥区和山东半岛北部近岸泥区正好对应于海底淤积区，辽东半岛南岸的狭长泥带也对应于淤积条带。这些结果表明海底冲淤的计算结果符合泥区是现代连续沉积区的观点。 沉积速率计算值与实测值相符，沉积速率的分布与海底沉积物的分布对应良好。中部泥区对应着与其规模和形状相似的沉积速率为0.1庄山刀a以下沉积区;烟台和蓬莱近海泥区也对应着两小块沉积速率为0.5nln亡a以下的细颗粒沉积区。其它海区为冲刷速率大小不等的海底冲刷区。这一结果与实际相符。 上面的结果(沉积物净，海底冲淤，沉积速率，底应力，活动层厚度)都表明:北黄海中部必定是一个泥质沉积区。由于模型中没有包含上升流的影响，因此，上升流的存在不是形成泥质沉积的必要条件;但是在一定程度上，上升流的存在可能影响泥区的沉积速率。更多还原

【Abstract】 Straits linking two bodies of sea water provides a channel for the transport and exchange of a variarity of materials (e.g. sediment, nutritients, contaminants, and microorganisms). In the field of marine geology, it is of particular interest to consider sediment sxchange through the starit. Because of the highly variable topological and hydrodynamic condifitions at a strait, the distribution of sediment is complex, with a large gradient in grain size parameters. This is a favorable condition for the understanding of the processeses and mechanisms of sediment transport and the associated local and regional effects. As a channel for the exchange of sediment between the Bohai and the Yellow Seas, the Bohai Strait is a good example.On the basis of considerationbs of the physical domain, the characteristics of the tides and sediment distribution patterns of the Bohai Strait, a 2-D horizontal model has been designed to study the long-term transport of sediment and accumulation over the Bohai Strait region. The model output is consistant with field observations, and can be used to explain patterns of long-tern transport and deposition of sediment in the study area.The vertically averaged current velocity is transferred into the current velosity at 1 m above the seabed using the Von Karman-Prandtl equation. Such a transformation is proved to be suitable in the study area by the verification using the ADCP data from 4 stations within the Strait. An expression is derived using basical concepts of physics (i.e. mass conservation), to define the relationship between sediment transport rate and vertical flux of sediment to the seabed. Using this method, satisfactory results about the evolution of the seabed are obtained, which is consistent with in situ observations. This method is better than the traditional method that relates the divergence of sediment transport rate to the deposition rate.The output of the tidal modelling reaches the required precision according to a comparison between the calculated tidal amplitudes/phases and the observed ones at 42 coastal tide gauge stations. Thus, the co-tidal patterns from calculations match observations, indicating .the validity of the tide model.The distributing patterns of the Eulerian residual currents of the four major tide constituents (i.e. M2, S2, Ol and Kl) imply that fine-grained sediment transport over the central mud of the northern Yellow Sea is weak. The Eulerian residual currents of Kl and S2 respectively form an anti-clockwise eddy near the coastal mud-deposit area of northern Shandong Peninsula, which may increase the deposition rate of mud. Although the patterns of residual currents are likely to reflectthe patterns of fine-grained sediment transport, it is difficult to relate such patterns to the transport of coarse-grained sediment.The result of long-term net sediment transport calculations confirms the hypothesis proposed by Cheng (2000) that in this area transport of sediment directed to northeastward occurs in addition to the main trend of transport towards the east. In the central mud of the northern Yellow Sea there lies an anti-clockwise eddy, indicating that sediments converge here, and once again confirming the conclusion reached by Cheng (2000) that sediment convergence occur in the central northern Yellow Sea. Off the south coast of Liaodong Peninsula, the net transport patterns from the model and from grain size trend analysis (Cheng, 2000) differ. The results of grain size trend analysis for this particular location is in doubt, because erosion is taking place here and the premise of the use of trend analysis is violated.Excellent correlation exists between the distribution of bottom shear stress and that of sediment types. Low shear stress occurs in the central mud area; where only fine-grained sediment can be imported by weak tidal currents. Once settled into the bed, it is difficult for set the sediment into motion. Therefore, the central mud represents an area of continuous depositon of fine-grained sediment.Good corre更多还原