Sediment Transport in Rivers and Coastal Waters     

YANG  Shu-qing 《中国海洋工程》2003,17(4):527-540

Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.  相似文献   

耗氧速率(OUR)测量方法的实验研究   总被引：4，自引：0，他引：4  

李冰  孙英兰  李玉瑛 《中国海洋大学学报(自然科学版)》2006,36(3):456-460

目前多采用分批实验法和呼吸测量仪测量耗氧速率,而耗氧速率的测量对于研究活性污泥数学模型中的动力学参数及废水特性鉴定具有重要意义。本文根据OUR测量方法的基本原理设计了1种简易的OUR测量装置,为检验测量装置的有效性,设计了相关实验进行验证。在内源呼吸实验中,测定了所用活性污泥的内源呼吸速率是5.1mgO2/L·h,污泥的衰减系数是0.0137h-1,比文献值略高。基质降解实验对人工配水(葡萄糖和淀粉)的耗氧速率进行了测定,实验结果显示有3个显著不同的耗氧速率,分别为35mg/L·h,13mg/L·h,6mg/L·h,它们各代表葡萄糖降解、淀粉降解和内源呼吸的速率。内源呼吸速率高于前1个实验是由于基质降解过程中污泥量增加所致。并计算出异养菌产率系数Kd为0.63mgVSS/mgCOD,Kd略低于文献值。实验结果证明,该装置能很好的实现测量目的。  相似文献   

Accumulation of organic and inorganic carbon in Pliocene–Pleistocene sediments along the SW African margin     

Jacques Giraudeau  Philip A. Meyers  Beth A. Christensen   《Marine Geology》2002,180(1-4):49-69

The Ocean Drilling Program Leg 175 recovered a unique series of stratigraphically continuous sedimentary sections along the SW African margin, an area which is presently affected by active coastal upwelling. The accumulation rates of organic and inorganic carbon are a major component of this record. Four Leg 175 sites (1082, 1084, 1085, 1087) are chosen as part of a latitudinal transect from the present northern to southern boundaries of the Benguela Current upwelling system, to decipher the Pliocene–Pleistocene history of biogenic production and its relationship with global and local changes in oceanic circulation and climate. The pattern of CaCO₃ and C_org mass accumulation rates (MARs) over 0.25-Myr intervals indicates that the evolution of carbon burial is highly variable between the northern and the southern Benguela regions, as well as between sites that have similar hydrological conditions. This, as well as the presence over most locations of high-amplitude, rapid changes of carbon burial, reflect the partitioning of biogenic production and patterns of sedimentation into local compartments over the Benguela margin. The combined mapping of CaCO₃ and C_org MARs at the study locations suggests four distinct evolutionary periods, which are essentially linked with major steps in global climate change: the early Pliocene, the mid-Pliocene warm event, a late Pliocene intensification of northern hemisphere glaciation and the Pleistocene. The early Pliocene spatially heterogeneous patterns of carbon burial are thought to reflect the occurrence of mass-gravitational movements over the Benguela slope which resulted in disruption of the recorded biogenic production. This was followed (3.5–3 Ma) by an episode of peak carbonate accumulation over the whole margin and, subsequently, by the onset of Benguela provincialism into a northern and a southern sedimentary regime near 2 Ma. This mid and late Pliocene evolution is interpreted as a direct response to changes in the ventilation of bottom and intermediate waters, as well as to dynamics of the subtropical gyral circulation and associated wind stress.  相似文献   

The recovery of the Barents Sea capelin (Mallotus villosus) from a larval point of view     

Fossum  P. 《ICES Journal of Marine Science》1992,49(2):237-243

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The intertidal erosion rate of cohesive sediment: a case study from Long Island Sound   总被引：2，自引：0，他引：2  

Y. H. Wang   《Estuarine, Coastal and Shelf Science》2003,56(5-6):891-896

Over the past decades, many attempts have been made to generate useful bottom erosion models for the study of cohesive sediment movement. This study addresses some of the key questions involved in determining the functional relationship between erosion rate and bottom shear stress. Current, wave, and turbidity data were collected from a bottom mounted instrument array in a moderately energetic estuarine environment. The bottom shear stress was calculated from a wave–current interaction model. The erosion rate was derived from the observed sediment concentration using a vertical mixing model. Examination of the relationship between erosion rate and bottom stress showed that the erosion rate varied at intertidal frequency. When averaged over the tidal fluctuation, the erosion rate remained approximately constant at low stress, but increased sharply when the shear stress rose above a critical value. This suggests two-stage erosion. The bed has a layered structure, in which a thin layer of loose, high water content material overlies a more consolidated bed. The top layer of high water content material (fluff) was easily disturbed and re-suspended by tidal currents, but the consolidated bottom layer was eroded only under conditions of high shear stress.  相似文献   

Consequences of growth variation in northern Baltic herring for assessment and management     

Rahikainen  Mika; Stephenson  Robert L. 《ICES Journal of Marine Science》2004,61(3):338-350

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浙江省海塘塘顶高程的确定   总被引：10，自引：1，他引：10  

黄世昌  周骥等 《海洋工程》2001,19(4):67-71

介绍了浙江省海塘塘顶高程确定时所涉及的波浪爬高，越浪量等的计量，同时分析了1997年后浙江省海塘塘顶高程确定的方法，由已建海塘的塘顶高程分析可见，在背水坡和塘顶有保护措施的情况下，采用允许最大越波流量来控制海塘塘顶高程，可适当降低塘身高度。  相似文献   

湄洲湾夏季油的分布特征与防护对策     

王宪  陈于望 《台湾海峡》1996,15(3):265-269

本文根据１９９２年夏季对湄洲湾水质环境质量调查资料，对该海区海水中油的含量及分布特征进行了分析研究。结果表明：湄洲湾夏季表层海水油的含量为５－５１μｇ／ｄｍ＾３，平均值为１９．８μｇ／ｄｍ＾３。海水的混合系数较小，高潮和低潮时油含量分布的差异，除了与陆源污染源分布有关外，主要是由水文动力学条件所决定。  相似文献   

Geological Characteristics and Distribution of Submarine Physiographic Features in the Taiwan Region     

Ho-Shing Yu 《Marine Georesources & Geotechnology》2003,21(3):139-153

The sea floor topography around Taiwan is characterized by the asymmetry of its shallow and flat shelves to the west and markedly deep troughs and basins to the south and east. Tectonics and sedimentation are major controls in forming the submarine physiographic features around Taiwan. Three Pliocene-Quaternary shelves are distributed north and west of Taiwan: East China Sea Shelf (passive margin shelf), the Taiwan Strait Shelf (foreland shelf), and Kaoping Shelf (island shelf) from north to south parallel to the strike of Taiwan orogen. Off northeastern Taiwan major morpho/tectonic features associated with plate subduction include E-W trending Ryukyu Trench, Yaeyama accretionary wedge, forearc basins, the Ryukyu Arcs, and the backarc basin of southern Okinawa Trough. Off eastern Taiwan lies the deep Huatung Basin on the Philippine Sea plate with a relatively flat floor, although several large submarine canyons are eroding and crossing the basin floor. Off southeastern Taiwan, the forearc region of the Luzon Arc has been deformed into five alternating N-S trending ridges and troughs during initial arc-continent collision. Among them, the submarine Hengchun Ridge is the seaward continuation of the Hengchun peninsula in southern Taiwan. Off southwestern Taiwan, the broad Kaoping Slope is the major submarine topographic feature with several noticeable submarine canyons. The Penghu Canyon separates this slope from the South China Sea Slope to the west and merges southwards into the Manila Trench in the northern South China Sea. Although most of sea floors of the Taiwan Strait are shallower than 60 m in water depth, there are three noticeable bathymetric lows and two highs in the Taiwan Strait. There exists a close relationship between hydrography and topography in the Taiwan Strait. The circulation of currents in the Taiwan Strait is strongly influenced by seasonal monsoon and semidiurnal tides. The Penghu Channel-Yunchang Ridge can be considered a modern tidal depositional system. The Taiwan Strait shelf has two phases of development. The early phase of the rift margin has developed during Paleoocene-Miocene and it has evolved to the foreland basin in Pliocene-Quaternary time. The present shelf morphology results mainly from combined effects of foreland subsidence and modern sedimentation overprinting that of the Late Pleistocene glaciation about 15,000 years ago.  相似文献   

黄河三角洲河道沉积规律研究Ⅱ. 建林边滩沉积作用机理     

范德江  陈彰榕  栾光忠 《中国海洋大学学报(自然科学版)》2001,31(2):237-242

通过对建林边滩沉积物粒度分布、粒度参数及水体流变性质的分析，阐述了黄河三角洲上河道水流属于牵引流范畴，与低含沙水流无本质上的差别，并探讨沉积物搬运和沉积的基本特征。  相似文献