泉州湾水体结构的潮周期变化   总被引：1，自引：0，他引：1  

刘浩  骆智斌  潘伟然 《台湾海峡》2009,28(3):316-320

泉州湾6个站点的观测数据显示：内湾涨潮流历时由底层向表层逐渐变短,而落潮流历时则逐渐变长;同时,各个站点实测的盐度水深结构也具有明显的潮周期变化特征,这可能与局地水体的层化和混合机制的交替变化密切相关．进一步定量分析S2站位上影响水体结构变化的四种机制发现：外湾的河口环流作用与潮汐张力、风混合以及潮汐混合作用相比要小一个量级．在一般天气条件下的大潮周期,潮汐混合与潮汐张力相互竞争是导致水体结构交替变化的根本原因;小潮周期由于潮流混合作用减弱,水体层化现象得以持续较长时间,风的搅动在特定时刻可以起到削弱层化结构的作用．  相似文献   

长江口河口锋的悬沙及动力特征初探     

毕世普  黄海军  庄克琳  周良勇 《海洋科学》2009,33(12):12-17

通过对2002年9月、2003年4月和2004年10月在长江口滨外区多船同步定点观测的数据进行分析,捕捉到了长江口河口锋带位置,并利用调查数据分析了河口锋带的动力特征.结果表明:长江口河口锋的位置大约位于122°10′E,30°50′N至122°20′E,31°00′N一线附近,在河口锋带有着较为强烈的河海相互作用,流速不符合典型的对数流速曲线,河水与海水的相互消长局限于海面以下5 m的表层范围,观测表明在河口锋面区悬浮泥沙为泥沙流伏在海水之上输运.  相似文献   

从海岸地貌学看河海划界的可操作性     

高抒 《海洋学研究》2009,27(Z1)

根据河海划界的可操作性的要求,探讨了海岸地貌学指标在河口区划分中的作用,并通过对河口区与河流、海洋之间的动态联系的阐述,提出河口区管理方式的建议.河口是海岸带陆海相互作用的典型环境,具有物理、化学、地质、生物和环境等多种复杂动力学过程,每一个河口都是高度个性化的.在为数不多的体现河口共性的参数中,海岸地貌学指标可用来确定河口区的内、外边界.根据河流水力学特征和河口过程的可容空间范围特征,河口-河流的分界点可用B-L曲线(B为河岸宽度,L为距离原点沿河流轴线的累积长度)上的拐点位置来表示.而按照河口为"半封闭水域"的定义,河口-海洋分界线可采用围封河口水域的海岸线的包络线.河口水域受到河流和海洋的双重影响,且河口区的自然演化和人类开发活动也会影响河流和海洋.因此,在我国河口区管理上应建立海洋和其他管理部门之间的协调机制.  相似文献   

Contrasts between estuarine and river systems in near-bed turbulent flows in the Zhujiang (Pearl River) Estuary, China   总被引：5，自引：0，他引：5  

Huan Liu  Chaoyu Wu  Weiming Xu  Jiaxue Wu   《Estuarine, Coastal and Shelf Science》2009,83(4):591-601

A bottom-mounted instrumental tripod was deployed in the tidally energetic Zhujiang (Pearl River) Estuary to examine the contrasting properties of the bottom boundary layer (BBL) flows between estuarine and tide-affected river systems. Three aspects of the BBL flows were investigated to understand the mechanism of the turbulence responses to the large-scale ambient forcing: the flow structures (profile, anisotropy, and spectra), shearing strains and stresses, and the balance of turbulent kinetic energy (TKE). Single log-law profiles and turbulence anisotropy predominated in the two systems, but the non-log regime and stronger anisotropy occurred more frequently at the slack tide in the estuary. The ADV-based turbulence intensities and shearing strains both exceeded their low-frequency counterparts (frictional velocities and mean shears) derived from the logarithmic law. On the contrary, the ADV-based Reynolds stresses were smaller than the log profile-derived bottom stresses, so the hypothesis of a constant stress layer cannot be well satisfied, especially in the river. The bandwidth of the inertial subrange in the river was of one decade larger than in the estuary. The balance between shear production and viscous dissipation was better achieved in the straight river. This first-order balance was significantly broken in the estuary and in the meandering river, by non-shear production/dissipation due to wave-induced fluctuations or salinity/sediment stratification. All these disparities between two systems in turbulence properties are essentially controlled by the anisotropy induced by the large-scale processes such as secondary currents, density stratification. In conclusion, the acceleration of unsteady flows determines the profile structure of the BBL flow, and turbulence anisotropy results in the invalidation of the phenomenological relations such as the constant stress hypothesis and the first-order TKE balance.  相似文献   

长江口南汇咀岸滩围垦工程潮流数值模拟研究   总被引：3，自引：0，他引：3  

付桂  李九发  戴志军  吴荣荣  虞志英 《海洋湖沼通报》2007,(4):47-54

南汇咀岸滩地处长江河口最大浑浊带,是长江河口淤涨速度最快的岸滩,是上海市规划围垦的重点区域。目前上海在南汇咀岸滩上已实施了围垦工程,围垦工程改变了长江口南汇岸线,也改变了南汇咀的水动力条件。为了解围垦工程实施后的水动力条件的变化,本文利用Delft3D-flow建立了长江口-杭州湾垂向平均的二维水动力模型,在对现场实测资料验证良好的基础上,对南汇咀海域围垦工程前后的潮流场进行了数值模拟,就围垦工程对周边海域的影响进行了分析研究。同时,对比南汇咀围垦前后的海图,采用GIS方法分析地形变化,利用地形变化来进一步验证海域的水动力变化。结果表明:工程后,杭州湾北岸流速增强,地形冲刷加剧;南汇东滩流速减弱,地形淤涨。  相似文献   

我国近海陆架锋面与生态效应研究回顾          下载免费PDF全文

刘东艳  吕婷  林磊  韦钦胜 《海洋科学进展》2022,40(4):725-741

海洋锋面存在于特征明显不同的2种或多种水系或水团交界处,锋面区域形成的次生环流和辐聚作用可显著影响到海洋中的物质输运与生物生产,故受到海洋学家的广泛关注。研究发现,我国近海陆架存在14个永久性的准静止锋面（渤海海峡锋面、山东半岛沿岸锋面、苏北沿岸锋面、西韩湾锋面、京畿湾锋面、济州岛西锋面、长江环形浅滩锋面、闽浙沿岸锋面、黑潮锋面、台湾沿岸锋面、闽粤沿岸锋面、珠江口沿岸锋面、琼东锋面和北部湾锋面）,且部分海域观测到双锋面、穿刺锋面和锋面波等现象。它们与陆架环流及其他动力过程（如：涡旋、内波等）共同控制着我国边缘海的物质能量输运与交换以及生物生产力格局。近岸物质沿锋面、跨锋面输运与锋区的垂向输送过程对我国边缘海生物地球化学循环和生态过程存在显著季节性影响。冬季到春季,沿岸锋面松弛能够加强物质从近岸向陆架的输运,进而在空间上调制春季藻华暴发的时间与量级;夏季到秋季,我国边缘海存在显著的潮汐锋面系统,锋面的辐聚效应以及次级环流可显著提高锋面区域的营养盐浓度和改善光照水平,对浮游植物的生长聚集起到促进作用,故在富营养化的河口与沿岸海域,锋面区域容易成为赤潮或缺氧高发区。此外,锋面的物理屏障作用使得两侧水团保持相对独立的物理与化学特征,因而在我国边缘海生境区划和生物多样性梯度变化等方面扮演重要角色,这些研究对认识我国边缘海物质循环与生物生产的控制机制具有重要作用。未来仍需充分结合观测与卫星资料,运用多过程耦合的高分辨率模型,深入认识锋面的精细结构与动态变化,加强亚中尺度和小尺度过程及其生态效应的研究。  相似文献   

Salt marsh plants (Juncus maritimus and Scirpus maritimus) as sources of strong complexing ligands     

Ana P. Mucha  C. Marisa R. Almeida  Adriano A. Bordalo  M. Teresa S.D. Vasconcelos 《Estuarine, Coastal and Shelf Science》2008

This work aimed to evaluate, in vitro, the capability of roots of salt marsh plants to release strong Cu-complexing ligands and to ascertain whether Cu contamination would stimulate ligands' exudation or not. The sea rush Juncus maritimus and the sea-club rush Scirpus maritimus, both from the lower Douro river estuary (NW Portugal), were used. Plants were collected seasonally, four times a year in 2004, during low tide. After sampling, plant roots were washed for removal of adherent particles and immersed for 2 h in a solution that matched salinity (3) and pH (7.5) of the pore water from the same location and spiked with Cu²⁺ in the range 0–1600 nM to obtain plant exudates. In the final solutions as well as in sediment pore water total dissolved Zn and Cu, Cu-complexing ligand concentrations and the respective conditional stability constants (K_CuL^′) values were determined by voltammetry. This study demonstrated that plants are able to release, in a short period of time, relatively high amounts of strong Cu-complexing ligands (56–265 nmol g_root⁻¹), which differed among plants and sampling site but were independent of the season. Cu contamination did not stimulate exudation of Cu-complexing ligands. On the other hand, in media contaminated with Cu both plants accumulated relatively high amounts (29–83%) of the initially dissolved Cu, indicating that they have alternative internal mechanisms for Cu detoxification. Cu exchange between roots and medium (either accumulation in contaminated medium or release in the absence of Cu) was more intense for S. maritimus than for J. maritimus. It was observed that exudate solutions obtained in the absence of added Cu and sediment pore water (the densities of roots observed inside the salt marsh where comparable to those used in the in vitro experiments), displayed similarities in terms of total dissolved metals, Cu-complexing ligands concentrations, values of K_CuL^′ (12 < log K_CuL^′ < 14), as well as patterns of variation among seasons (only observed for Zn). These results are novel and point out that salt marsh plants may be the source at least partially of the strong organic ligands found in the sediment pore water in shallow marginal areas. The capability of salt marsh plants to release strong organic ligands into the environment, conjugated with their known capacity to oxidize anaerobic sediment around roots, indicate that these plants can play a role in controlling metal speciation in the water/sediment interface.  相似文献   

Metal pollution of estuarine sediments caused by leaching of acid sulphate soils     

Linda Nordmyr  Mats Åström  Pasi Peltola 《Estuarine, Coastal and Shelf Science》2008

This study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate (AS) soil landscapes in the Boreal Zone (Finland). The main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish-water estuary. In order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the Vörå River, which is one of the most heavily AS soil-impacted rivers in Finland and Europe. Two of the cores were rather deep (2.5 m and 4.0 m) and the others were shallow (0.4 m and 0.8 m). The results showed that an appreciable amount of aluminium (Al), cobalt (Co), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni) and zinc (Zn) were elevated in the surface and sub-surface of the sampled bottom sediments compared to the deeper sediment background levels. These metals are all known to be abundantly leached from the AS soils. At the site approximately 4 km away from the river mouth, the concentrations of Cd, Co, Mn, Ni and Zn were elevated 5–100 times as compared to the background levels and showed an intriguing cyclic pattern, most likely reflecting seasonal leaching dynamics in the AS soil landscapes. In contrast, metals that are not abundantly leached from AS soils, i.e. chromium (Cr), iron (Fe) and vanadium (V) had consistently low concentrations throughout all sediment cores. The elevated metal concentrations in the top layers of the sediments in the estuary are alarming. The continuous land uplift of the region combined with the episodic rapid declines in pH may result in short and long term extensive release of metals. This, in turn, may have significant effects on the trace-metal contents in the Gulf of Bothnia and the entire Baltic Sea.  相似文献   

Estuarine classification and response to nitrogen loading: Insights from simple ecological models     

D.P. Swaney  D. Scavia  R.W. Howarth  R.M. Marino 《Estuarine, Coastal and Shelf Science》2008

Estuaries exhibit a large range in their responses to nitrogen loadings determined in part by characteristics of the driver, such as magnitude and frequency, but also by such intrinsic characteristics as physical/chemical factors (e.g., depth, volume, hypsometry, salinity, turbidity) and biological factors (e.g., nature of ecological communities, trophic interactions). To address the richness of estuarine response to driver variables, the aim ultimately is to establish a simple estuarine classification scheme, beginning with a river-dominated subset of estuarine systems and focusing on the role of water residence time in the estuary. Residence time (or flushing time) is related to other drivers (streamflow, nutrient, and sediment loads) and drives much of the biological response of estuaries because of flushing effects on plankton, temperature, nutrients, and light. Toward this goal, nutrient–phytoplankton–zooplankton (NPZ) models have been used to examine a range of subjects including effects of nutrient limitation and zooplankton predation on phytoplankton dynamics and fish predation. This class of model can admit a wide range of behavior, including multiple steady-states and oscillatory behavior. The NPZ equations include terms for nutrient recycling, phytoplankton settling, benthic regeneration, and zooplankton mortality. Analysis of the equations suggests that both the nature of nitrogen loading (i.e., whether it is correlated with discharge or independent of it) and residence time are critical in determining the steady-state response of the system.  相似文献   

Stable isotopes in juvenile marine fishes and their invertebrate prey from the Thames Estuary,UK, and adjacent coastal regions     

Chris D.B. Leakey  Martin J. Attrill  Simon Jennings  Mark F. Fitzsimons 《Estuarine, Coastal and Shelf Science》2008

Estuaries are regarded as valuable nursery habitats for many commercially important marine fishes, potentially providing a thermal resource, refuge from predators and a source of abundant prey. Stable isotope analysis may be used to assess relative resource use from isotopically distinct sources. This study comprised two major components: (1) development of a spatial map and discriminant function model of stable isotope variation in selected invertebrate groups inhabiting the Thames Estuary and adjacent coastal regions; and (2) analysis of stable isotope signatures of juvenile bass (Dicentrarchus labrax), sole (Solea solea) and whiting (Merlangius merlangus) for assessment of resource use and feeding strategies. The data were also used to consider anthropogenic enrichment of the estuary and potential energetic benefits of feeding in estuarine nursery habitat.  相似文献