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 共查询到11条相似文献,搜索用时 73 毫秒
1.
山东荣成湾月湖地区的潟湖-潮汐汊道体系   总被引:3,自引:0,他引:3  
潟湖-潮汐汊道体系为一复杂的反馈体系,其中任一参数的改变即可导致整个体系的复杂反映.以月湖为例探讨了潟湖地貌演化的过程中,及人工作用潟湖各主要参数的变化规律;提出了月湖目前由于人工围堵特别是残余坝基对潮流的限制作用,致使P/A值较高而饱满系数K值偏低,潟湖-潮汐汊道体系稳定性较差的问题.  相似文献   

2.
本文介绍了兰州地区历次重力固体潮测量的概况,给出了不同仪器历次测量所得的重力潮汐参数。对比分析了Geo—765重力仪和改型后的GS11—150重力仪观测资料月调和分析主波潮汐因子的重复精度,评价了改型后的GS11—150重力仪今后对兰州地区地震的监测能力。文中还给出了该仪器改型前在天水观测的部分结果。  相似文献   

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4.
This paper presents results of investigations (1983–1992) into rates of change, morphology and processes occurring during the current erosional phase in a Morecambe Bay cyclic saltmarsh, in which it has narrowed from c. 1000 m (1975) to c. 150 m (1992). Monthly monitoring of marsh edge erosion and creek knickpoint retreat has revealed temporal and spatial variations. Highest frequency changes of low magnitude coincided with non-storm conditions and overmarsh tides above 5·80 m OD, which submerged the whole marsh. Less frequent changes of greater magnitude were associated with both overmarsh tides and strong onshore winds over 15 ms?1, which generated high energy waves. The lowest frequency change of greatest magnitude occurred during an extreme onshore storm event and surge. Morphologically, during the erosional phase, a low angled landward slope was generated as erosion of the c. 0·5 m high active seaward cliff coincided with vertical accretion of 0·07 ma?1 of relatively coarse sediment on the marsh surface immediately landward. Tidal hydrodynamics strongly influence the saltmarsh, which is confined to the upper 2·5 m of the macrotidal range (maximum c. 10·5 m). During overmarsh spring tides (maximum creek flood flow rate 0·13 ms?1, up to bankfull level), flooding begins over lower landward creek banks before submerging the higher marsh edge. During ebb tides, water trapped by this higher edge can escape seaward only via the creeks (maximum ebb velocities 2·07 ms?1 below bankfull level). Wave erosion also is limited to spring tides. Monthly mapping of the Kent Estuary channel pattern seaward of the saltmarsh showed that medium term higher erosion rates were related to the presence of a large channel, which lowered the adjacent creek base level and allowed larger waves to attack the marsh edge than when a sandbank flanked the marsh. Major River Kent channel shifts appear to initiate accretional or erosional phases of cyclic saltmarsh development.  相似文献   

5.
福建深沪湾海底古森林与全新世强古地震   总被引:2,自引:0,他引:2  
介绍了深沪湾海底古森林遗迹,指出了海底古森林与古地震的关系,给出了深沪湾全新世强古地震的依据。  相似文献   

6.
It have been measured the denitrification rates (DR) of sediment in Saginaw Bay, Lake Huron, by N2 production method. Triplicate samples of sediment core were collected at two GLERL long-term monitoring sites of the Bay in July and August of 1995. The DR are 48.81 -24.99 and 32.81-40.51 micromol N2 -2h-1 in the Inner and Outer regions of Saginaw Bay, respectively.The characters of DR in Saginaw Bay were studied also in this paper. The DR were influenced by the interactions between the Saginaw River as a main pollution source and the Lake Huron as a reservoir of high quality water. The impacts of zebra mussels (Dreissena Polymorpha) on denitrification in Saginaw Bay, Lake Huron, were discussed, Significant differences in NH4+ exchange fluxes were detected in the inner and outer bays. The molar ratios of N2:TIN were similar at both sampling sites. Measured DR were positively correlated to O2 consumption rates in the headspace. Additionally, a negative correlation between NH4+ and NO3- concentrations in the overlying water was found.  相似文献   

7.
太湖贡湖湾水生植被分布现状(2012年)   总被引:4,自引:2,他引:4  
贡湖湾是无锡和苏州两市的重要水源地,随着近些年太湖水质的急速恶化,贡湖湾蓝藻暴发现象日益严重,危及饮水安全.为提供贡湖湾水资源管理的理论依据,于2012年开展贡湖湾水生植被野外调查.对8个断面进行为期5天的调查,结果表明:(1)共记录贡湖湾水生植物20科27属34种,单子叶植物和沉水植物分别为优势分类群和生态型;(2)贡湖湾水生植被分布区面积占总水域面积的45.35%,为典型半草型湖泊;(3)共有8种水生植物群落分布,其中马来眼子菜群落分布区面积和生物量最大;(4)贡湖湾水生植被总体表现出北部无水生植被分布,东部生物量高、群落及物种组成复杂,其他区域生物量小、群落组成单一的分布格局.水质恶化和插网捕鱼对贡湖湾水生植被分布现状存在影响,过度清淤可能是造成北部水域裸露的原因.结合贡湖湾水生植被分布现状分析结果,建议在贡湖湾水生植被管理中要开展北部裸水区植被修复,促进湾口区域马来眼子菜群落生长,加强对"引江济太"工程上游来水和贡湖湾水质的监测,并注重外来入侵植物尤其是水盾草群落的监测.  相似文献   

8.
介绍了深沪湾沿岸地层、构造、海底古森林及晚更新世古牡蛎滩遗迹,深沪湾的地壳运动与古环境变迁;研究了海底古森林和晚更新世古牡蛎滩的成因。  相似文献   

9.
At present, there is a very limited information on the levels and distribution of dissolved metals in Manila Bay. In this study, the horizontal and vertical distribution of operationally defined species (labile, bound and total) of dissolved copper (Cu), cadmium (Cd) and zinc (Zn) were determined using differential pulse anodic and cathodic stripping voltammetry in water samples obtained from 18 stations in November 1998. In addition, the 24-h variability in the concentrations of these species at different depths in the water column was determined. These measurements were complemented by the determination of temperature, salinity, dissolved oxygen, chlorophyll a, particulate organic carbon and nutrients. Results showed that more than 50% of total dissolved copper and cadmium were labile while 50% of total dissolved zinc was organically bound. Vertical profiles showed that Cu, Cd and Zn concentrations were generally high at the surface. Zinc and cadmium were characterised by the presence of a mid-depth minimum while copper did not show any clear vertical trend.

Dissolved Cu concentrations during the spatial and diurnal samplings ranged from 0.32 to 6.95 nM and 1.52 to 45.65 nM, respectively. For Cd, the concentrations in 18 stations ranged from 0.05 to 2.92 nM, and from 0.03 to 2.42 nM over a 24-h period. Zn concentrations ranged from 2.48 to 147.43 nM and 2.87 to 88.27 nM during the spatial and diurnal samplings, respectively. The large variation in the concentration of Cu, Cd and Zn in the bay was observed to be associated with the presence of a large vertical density gradient in the water column, which appeared to limit the exchange of materials between the surface and bottom waters. Elevated levels of these metals near point sources suggest anthropogenic inputs in the bay.  相似文献   


10.
This study reports the role of waves, tide, wind and freshwater discharges over the sea level in Óbidos Lagoon, a coastal system connected to the sea through a narrow and shallow mobile inlet. To address the hydrodynamic features of this coastal system, the relative importance of different physical forcings were evaluated. For this purpose, observations together with realistic and idealized numerical modeling were used. Both model and measurements show that the lagoon sea level remains above offshore sea level during storm wave periods. Hence, a simplified inlet-lagoon idealized model was described through mathematical expressions, to understand and highlight the physical processes responsible for sea-level elevation.  相似文献   

11.
普里兹湾位于南极洲东部大陆边缘,其深部地壳结构特征对认识白垩纪冈瓦纳古陆裂解和新生代大陆边缘形成具有重要意义.本文利用重磁、多道反射地震、声纳浮标折射地震和ODP钻井数据对普里兹湾海域的深部地壳结构进行了研究.研究结果显示,普里兹凹陷表现为典型的盆地负重力异常特征,其沉积基底较深,而在四夫人浅滩为高幅重力正异常,其沉积基底普遍抬升.在大陆架中部存在SW-NE向条带状基底的抬升,且呈朝NE向逐渐变深的趋势.在中大陆架外侧,均衡残余重力异常呈V字形负异常条带状分布,其两翼分别与四夫人浅滩和弗拉姆浅滩外的大陆坡相连.该异常带在大陆架中部向陆的偏移可能是由于古大陆架边缘的地形影响,推测其与普里兹冲积扇同属于洋陆过渡带向陆的部分,在重力模拟剖面表现为地壳向海逐渐减薄.普里兹冲积扇的地壳厚度较薄,平均为6 km,最薄处可达4.6 km,并且根据洋陆过渡带向海端的位置,推测可能属于接近洋壳厚度的过渡壳.重力异常分区的走向与兰伯特地堑在普里兹湾的构造走向基本一致,可能主要反映了二叠纪—三叠纪超级地幔柱对普里兹湾的裂谷作用的影响.该区域的自由空间重力异常和均衡残余异常均表现为超过100×10-5m/s2的高幅正异常特征,可能由位于大陆架边缘的巨厚沉积体负载在高强度岩石圈之上的区域挠曲均衡作用所导致,可能与该区域第二期裂谷期之后的沉积间断以及快速进积加厚的演化过程有关.普里兹湾磁力异常的走向与重力异常明显不同,大致可分为东北高幅正异常区和西南低幅异常区.重磁异常在走向上的差异反映高磁异常主要来源于岩浆作用形成的铁镁质火成岩的影响,并且岩浆作用的时代不同于基底隆升的时代,而可能形成于前寒武纪或者南极洲和印度板块裂谷期间(白垩纪).  相似文献   

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