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1.
For the first time, the results of studying the hydrochemical characteristics of bays in the Bratsk Reservoir, subject to the effect of forest harvesting operations are given. The obtained data include the concentrations of NO3?, NO2?, NH4+, PO4-3, SiO2, phenols, oil products, and organic matter and the oxygen regime of water in the bays. The concentration and distribution in water of biogenic elements and O2-typical of wood decay processes-demonstrate the high self-purification capacity of ecosystems in the majority of bays. At the same time, water of some bays shows signs of eutrophication and high concentrations of phenols and oil products.  相似文献   

2.
The coastal water bodies that separate from White Sea water area due to Kandalaksha coast rise are examined. The hydrological and hydrochemical characteristics of these water bodies are found to notably differ from these in the bays and straits connected with them. Extreme values of water temperature and salinity were recorded. High concentrations of oxygen (>20 mg/l) were recorded in the near-surface water layers and high concentrations of hydrogen sulfide (>90 mg/l) in bottom waters. The species composition of phyto- and zooplankton was found to be poor. The characteristics of enzymatic destruction in subsurface waters of lakes are an order of magnitude greater than those in White Sea open areas.  相似文献   

3.
Runup of Tsunami Waves in U-Shaped Bays   总被引：2，自引：0，他引：2  
The problem of tsunami wave shoaling and runup in U-shaped bays (such as fjords) and underwater canyons is studied in the framework of 1D shallow water theory with the use of an assumption of the uniform current on the cross-section. The wave shoaling in bays, when the depth varies smoothly along the channel axis, is studied with the use of asymptotic approach. In this case a weak reflection provides significant shoaling effects. The existence of traveling (progressive) waves, propagating in bays, when the water depth changes significantly along the channel axis, is studied within rigorous solutions of the shallow water theory. It is shown that traveling waves do exist for certain bay bathymetry configurations and may propagate over large distances without reflection. The tsunami runup in such bays is significantly larger than for a plane beach.  相似文献   

4.
Spatial and temporal variability of heavy metals concentrations in the Ivan'kovo Reservoir bottom sediments was studied. It was found that for the period of 1983–1998, their content largely decreased in many sections of the reservoir, with the exception of individual deep-water channel stretches and certain bays. The character of vertical distribution of microelements in the bottom sediments is shown to be related to the level of contamination and character and rate of water exchange in the reservoir.  相似文献   

5.
A three-dimensional model was established to investigate water exchange in coastal waters, and applied to Qinzhou Bay(QZB) in the South China Sea. Given the strong tidal current in QZB, a half-life time was calculated for water exchange by filtering the tidal signal from the concentrations of a conservative substance. In a control run driven by the tide, without external inputs and an open boundary concentration of zero, it was estimated that the average half-life time in QZB was 54.8 d. Numerical experiments showed that wind accounted for an 11.9% reduction in the half-life time to 48.3 d. When rivers were included in the model, the half-life time decreased by 74.6% to 13.9 d. Sensitivity experiments showed that the half-life time for water exchange was greatly affected by the concentration of the conservative substance which was used at the open boundary. In response to 10,20, 30, and 40% increases in the boundary concentration, the half-life time increased to 91.5, 168.3, 186.2, and 229.1 d,respectively. Results also suggested that for coastal bays with large intertidal areas such as QZB, consideration of the wet and dry processes produced more accurate simulations of the hydrodynamics and the half-life times. Simulations, which did not incorporate wet and dry processes, were more than likely to have overestimated or underestimated the half-life times for water exchange.  相似文献   

6.
前期风场控制的太湖北部湖湾水动力及对蓝藻水华影响   总被引：7，自引：6，他引：1  
为明确前期风场对太湖北部湖湾水动力及蓝藻水华分布的影响,对2008年9月梅梁湾及贡湖湾水文、水质及气象开展了同步观测,结果表明:受前期东北风影响,梅梁湾及贡湖湾表层、中层及底层湖流流向均顺风向自湾内流向湾外,两个湖湾均不存在补偿流.表层湖流对风场变化响应敏感,而中场及底层流场对风场变化响应存在显著滞时.在偏南风作用下,梅梁湾表层湖流能快速形成顺时针环流.在偏西风作用下,贡湖湾表层湖流流向虽未发生偏转,但是湖流流速显著减小并导致流速沿水体垂向呈递增分布.观测期间水动力强度对太湖北部湖区叶绿素a浓度垂向分层及蓝藻水华水平漂移均具有重要影响.在水动力滞缓水域,蓝藻水华易在水表发生漂移堆积.在水动力强度较大水域,强烈的垂向混合作用能使蓝藻沿水深方向混合均匀,降低水华暴发风险.相对于水动力条件,营养盐对叶绿素a浓度空间分布的影响较弱.  相似文献   

7.
太湖水龄分布特征及“引江济太”工程对其的影响   总被引：1，自引：5，他引：1  
太湖作为典型的风生流湖泊,风场对水体运输和交换的过程起着重要的作用.基于环境水动力学模型EFDC源程序建立了染色剂模型以及水龄模型,借助水龄研究太湖水体的长期输运过程和更新速率特征,从而为太湖的调水工程管理提供科学依据.本文在研究春、夏、秋、冬季不同风场作用下太湖的水龄季节性分布特征的基础上,结合太湖实测风速、流量数据及"引江济太"工程调水运行的现状,着重分析了望虞河枢纽调水运行以及新沟河工程对太湖水龄分布的影响.数值试验的模拟结果表明:太湖水体交换受季风影响明显,春、夏季的水龄相对较大、水体交换较差;靠近湖流入口处的地方水龄较小,远离入口的地方水龄较大;水流流向与风向一致时水龄减小,水循环加快,反之则减慢.望虞河引水引工程能够减小贡湖及湖心区的水龄,加快贡湖湖区及湖心区的水循环;新沟河工程引水能够减小梅梁湖区的水龄,改善该湖区的水质.引水工程的实施对加快整个太湖的水循环做出重要贡献.  相似文献   

8.
Faroe Shelf Water (FSW) is the water mass that occupies the shallow parts of the Faroe Shelf, surrounding the Faroe Islands (62°N, 7°W). Intensive tidal mixing induces a high degree of homogeneity and the circulation system allows a partial isolation from surrounding waters. This water mass, therefore, supports a unique ecosystem of great importance for commercial fish stocks and studies have shown a clear dependence of the ecosystem on the physical processes that maintain this system and control the exchange between the FSW and the off-shelf waters. In order to identify and quantify these processes, a large observational dataset has been analysed and related to alternative theories. From this analysis, the extent and properties of the FSW have been quantified and the degree of stratification explained in terms of the Simpson–Hunter theory. The residual clockwise circulation system, which is responsible for the partial isolation from off-shelf waters, is shown to be mainly generated by tidal rectification. The typical exchange rate of water between the FSW and the off-shelf regimes has been determined by the use of simple models based on the heat and the salt budgets but the actual exchange rate is found to vary considerably in time and space. These results support earlier suggestions that this exchange is the main limiting factor for the phytoplankton spring bloom on the Faroe Shelf and that variations in exchange rate are responsible for the large inter-annual variation in spring bloom timing and intensity. The observations indicate that the on-shelf/off-shelf exchange intensity is not symmetrically distributed around the shelf, but rather concentrated around the narrow southern tip of the Faroe Shelf, where off-shelf waters during intensive exchange events may be imported all the way to the shore.  相似文献   

9.
The Amazon Macrotidal Mangrove Coast (AMMC) is a large (~7500 km2) contiguous mangrove fringe eastwards from the Amazon River mouth. It encompasses dozens of interconnected bays intercalated with mangrove peninsulas. Mud accumulates on the mangrove flats, whereas the bed of the bays and channels is generally sandy. In this study we investigated the circulation, sediment transport and deposition in a central site at one of these mangrove peninsulas. The study was undertaken during the dry period, when there is no influence of the Amazon River plume and minimum local freshwater inflow. Current and suspended-sediment concentration were monitored in a feeder channel on the mangrove flat along a ~1000 m section oriented along the peninsula axis. Sediment deposition was also measured on the flat. Our results show there was a strong exchange between the neighboring bays. Channel currents were flood dominant, reaching up to >1 m s−1, with residual water and sediment transport westwards. Suspended sediment concentration (SSC) in the channel was directly related to velocity magnitude, ranging between 50 and 350 mg L−1. The flat was flooded in a way that indicated the tidal wave evolves westwards, nearly parallel to the AMMC shoreline. Currents on the flats were much slower than those in the channel and showed slight ebb dominance. However, SSC was higher during the flood than ebb, clearly indicating settling during the current deceleration and limited erosion during the following ebb–flow acceleration. The net sediment transport across the section was 60 tons westwards for the period of the experiment (~4 days). The mean deposition rate was 0.006 kg m−2 s−1 (or 1.4 kg m−2 per tide), which was higher than rates from other reported assessments in mangroves. The set of results indicate very large internal sediment reworking in the AMMC. © 2019 John Wiley & Sons, Ltd.  相似文献   

10.
Tidal residual eddies and their effect on water exchange in Puget Sound   总被引：1，自引：0，他引：1  
Tidal residual eddies are one of the important hydrodynamic features in tidally dominant estuaries and coastal bays, and they could have significant effects on water exchange in a tidal system. This paper presents a modeling study of tides and tidal residual eddies in Puget Sound, a tidally dominant fjord-like estuary in the Pacific Northwest coast, using a three-dimensional finite-volume coastal ocean model. Mechanisms of vorticity generation and asymmetric distribution patterns around an island/headland were analyzed using the dynamic vorticity transfer approach and numerical experiments. Model results of Puget Sound show that a number of large twin tidal residual eddies exist in the Admiralty Inlet because of the presence of major headlands in the inlet. Simulated residual vorticities near the major headlands indicate that the clockwise tidal residual eddy (negative vorticity) is generally stronger than the anticlockwise eddy (positive vorticity) because of the effect of Coriolis force. The effect of tidal residual eddies on water exchange in Puget Sound and its subbasins was evaluated by simulations of dye transport. It was found that the strong transverse variability of residual currents in the Admiralty Inlet results in a dominant seaward transport along the eastern shore and a dominant landward transport along the western shore of the inlet. A similar transport pattern in Hood Canal is caused by the presence of tidal residual eddies near the entrance of the canal. Model results show that tidal residual currents in Whidbey Basin are small in comparison to other subbasins. A large clockwise residual circulation is formed around Vashon Island near entrance of South Sound, which can potentially constrain the water exchange between the Central Basin and South Sound.  相似文献   

11.

This paper is a review of research works concerning the nutrient transportation, transformation and exchange between water, sediment and biota in the lakes from the middle and lower reaches of the Yangtze River conducted in the context of project entitled “The Processes and Mechanism of Lake Eutrophication in Middle and Lower Reaches of Yangtze River”. All the lakes from this area are shallow lakes. According to the typical lake site research, the lakes from the middle and lower reaches of Yangtze River have a higher baseline of nutrition in the history. Normally the trophic status of these lakes can be categorized into medium-trophic or eutrophic Human activities have been enhanced during the last decades, which speed up the lake eutrophic process. Lake eutrophication control needs to reduce not only the external nutrient inputs from watershed but also the internal loading from the sediments. Investigations revealed that the lake sediments in this area are considerablly high in nutrition in which at most about 30% of phosphorus exists in the form of bio-available in the sediment. The surface sediment will exert great effects on the nutrient exchange between water-sediment interface via adsorption and release of nutrient. The nutrient release from the sediment in these shallow lakes is mainly in two ways, i.e. in the undisturbed condition the nutrient is released through diffusion created by the nutrient gradient from sediment to overlying water; whereas in disturbed condition, the nutrient release is determined by the hydrodynamic forcing intensity and the sediment resuspension. Metallic elements such as the iron, manganese and aluminium and the aerobic-anaerobic ambience will affect the release of nutrients. The disturbed release will increase the total nutrients in the water column significantly in the short period. At the beginning of sediment resuspension, the dissolved nutrient concentration will increase. This increase will be damped if the ferric oxide and aluminium are rich in sediment because of the adsorption and flocculation. This means that the lakes have capability of eliminating the nutrient loadings. Investigations for the lakes from middle and down stream of Yangtze River have suggested that most lakes have the self-cleaning capability. Dredging the control of the internal loading, therefore, is only applicable to the small lakes or undisturbed bays which normally are situated nearby the city or town and rich in organic materials in the sediment. In addition, the strong reduction condition and weak aeration of these lakes and bays make these small lakes and bays release much more bio-available nutrient and without much self-eliminating capability. Moreover, eutrophication induced algal bloom in these lakes will change the pH of water, which further induces the increase in the nutrient release. In turn, the increase in nutrient release promotes the growth of phytoplankton and results in severe algal bloom. For the heavily polluted water, research suggests that the biomass of bacteria and alkaline phosphatase activity will be higher corresponding to the higher concentration of nutrients, which accelerates the nutrient recycling between water, sediment and biota. Quick recycling of nutrient, in turn, promotes the production and biomass growth of microorganism and leads to more severe eutrophication. Further research work should focus on the nutrient transformation mechanism and the effects of microbial loop on the eutrophication.

  相似文献   

12.
This paper is a review of research works concerning the nutrient transportation, transformation and exchange between water, sediment and biota in the lakes from the middle and lower reaches of the Yangtze River conducted in the context of project entitled "The Processes and Mechanism of Lake Eutrophication in Middle and Lower Reaches of Yangtze River". All the lakes from this area are shallow lakes. According to the typical lake site research, the lakes from the middle and lower reaches of Yangtze River have a higher baseline of nutrition in the history. Normally the trophic status of these lakes can be categorized into medium-trophic or eutrophic. Human activities have been enhanced during the last decades, which speed up the lake eutrophic process. Lake eutrophication control needs to reduce not only the external nutrient inputs from watershed but also the internal loading from the sediments. Investigations revealed that the lake sediments in this area are considerablly high in nutrition in which at most about 30% of phosphorus exists in the form of bio-available in the sediment. The surface sediment will exert great effects on the nutrient exchange between water-sediment interface via adsorption and release of nutrient. The nutrient release from the sediment in these shallow lakes is mainly in two ways, i.e. in the undisturbed condition the nutrient is released through diffusion created by the nutrient gradient from sediment to overlying water; whereas in disturbed condition, the nutrient release is determined by the hydrodynamic forcing intensity and the sediment resuspension. Metallic elements such as the iron, manganese and aluminium and the aerobic-anaerobic ambience will affect the release of nutrients. The disturbed release will increase the total nutrients in the water column significantly in the short period. At the beginning of sediment resuspension, the dissolved nutrient concentration will increase. This increase will be damped if the ferric oxide and aluminium are rich in sediment because of the adsorption and flocculation. This means that the lakes have capability of eliminating the nutrient loadings. Investigations for the lakes from middle and down stream of Yangtze River have suggested that most lakes have the self-cleaning capability. Dredging the control of the internal loading, therefore, is only applicable to the small lakes or undisturbed bays which normally are situated nearby the city or town and rich in organic materials in the sediment. In addition, the strong reduction condition and weak aeration of these lakes and bays make these small lakes and bays release much more bio-available nutrient and without much self-eliminating capability. Moreover, eutrophication induced algal bloom in these lakes will change the pH of water, which further induces the increase in the nutrient release. In turn, the increase in nutrient release promotes the growth of phytoplankton and results in severe algal bloom. For the heavily polluted water, research suggests that the biomass of bacteria and alkaline phosphatase activity will be higher corresponding to the higher concentration of nutrients, which accelerates the nutrient recycling between water, sediment and biota. Quick recycling of nutrient, in turn, promotes the production and biomass growth of microorganism and leads to more severe eutrophication. Further research work should focus on the nutrient transformation mechanism and the effects of microbial loop on the eutrophication.  相似文献   

13.
Mikhailova  M. V.  Isupova  M. V. 《Water Resources》2019,46(6):825-831
Water Resources - The types and specific features of the internal and external water exchange in nontidal deltas are discussed. The results of hydraulic calculation of water exchange in the...  相似文献   

14.
目前大量景观类湖泊在人工布局下呈现形状不规整的特点,容易造成湖湾水体滞留形成死水区,水质恶化问题日益突出,本文以星湖为研究区域,建立基于环境流体生态动力学(EFDC)模型的星湖水动力—风场耦合模型,以水龄作为衡量水体交换速率的指标,设计12种工况模拟计算不同出入湖通道布局及流量配比、"引江济星"工程和风场对星湖水龄时空分布的影响.结果表明:星湖水龄存在季节性和空间性分布差异,春季主导风向与湖体流动主方向互斥,抑制了波海湖水体交换,导致水龄在春季较长,而秋季南西南季风促进中心湖等水体交换,致使水龄偏短,也反映出风向的影响存在湖区空间异质性,风向为南东南时星湖整体水龄最小;入湖口通道布局及流量配比对湖区水体交换速率存在影响,以外坑为波海湖入湖口且波海湖、中心湖、仙女湖入流比为4∶3∶3时,星湖整体水龄最小,拟建的青莲湖出水口和仙女湖出水口能有效加快青莲湖东北部和仙女湖东南部的水体交换速率;综合考虑调水引流效益、经济投资、生态开发和占地的成本,方案二为最优调水引流方案.本研究强调入湖口布局、流量大小和比例、及风场等因素对城市内湖水体置换的影响,为人为干扰下的景观湖泊的治理和管控提供科学支撑.  相似文献   

15.
Literary data have been used to assess the inflow of petroleum hydrocarbons (with river runoff, precipitation, wastewaters, sea transport, and at ice thawing) into different regions of the White Sea. The hydroecological CNPSi-model was used as an instrument to reproduce the annual dynamics of hydrocarbon concentrations at their parallel inflow and subsequent transformation in the waters of the nine White Sea regions (the bays of Kandalaksha, Onega, Dvina, and Mezen; the Solovetskie Islands; the deep-water part: Bassein, Gorlo, Voronka, and Chupa Bay). The calculations were based on normal annual values of monthly variations of water temperature, light intensity, and transparency, the morphometric parameters of the regions (water areas, mean depths, and water volumes) and water exchange between the regions and with the Barents Sea (calculated by a hydrodynamic model). The calculated concentrations of hydrocarbons, the biomasses and activity characteristics of hydrocarbon-oxidizing bacteria have been analyzed (their values were estimated for the 2-m surface water layer). The results of calculations were used to evaluate hydrocarbon balances for regions and the sea as a whole. The calculations demonstrate the balanced character of hydrocarbon fluxes, the balance discrepancy for the regions being <0.1–16.1%.  相似文献   

16.
Upwelling coastal systems can be used to understand how dissolved oxygen and biological productivity control the accumulation of redox-sensitive metals in marine sediments. The aluminium (Al), cadmium (Cd), iron (Fe), nickel (Ni), molybdenum (Mo), vanadium (V), total organic carbon (TOC), total nitrogen (TN) and total sulfur (TS) contents in surficial sediment collected from different water depths (30, 70, and 120?m) in three northern Chilean bays influenced by coastal upwelling and oxygen minimum zones (OMZs) were measured. Principal component analysis (PCA), cluster analysis, and Spearman?s rank correlation were used to identify the mechanisms responsible for the redox-sensitive metal accumulation. The content of redox-sensitive metals and organic components in sediment increased with increasing water column depth, whereas lithogenic metals decreased. In the Mejillones del Sur and Caldera bays, the enrichment factors of the redox-sensitive metals showed enrichment for all metals with depth. The Cd and V enrichments are mainly the product of biogenic flow to the seabed, and the Mo and Ni enrichments are due to preservation under low subsurface oxygen conditions. Sulfate reduction is not an important mechanism in the accumulation of redox-sensitive metals in the sediment of the three bays. The PCA showed that the behaviors of the redox-sensitive metals and organic components reflect differences in the effects of the OMZ in sediment along the coast of northern Chile, with a more intense OMZ in Mejillones del Sur bay and weaker OMZs in Caldera and Inglesa bays. However, the high degree of enrichment in redox-sensitive metals in Caldera Bay can be attributed to the intense activity of the mining industry near the bay, a situation that produces geochemical behavior similar to that observed in Mejillones del Sur Bay.  相似文献   

17.
Shallow water bays located in the western Arabian Gulf experience harsh environmental conditions. Some of these bays, including Manifa-Tanajib Bay System (MTBS), were also exposed to the 1991 oil pollution event. This study investigates the status of the macrobenthos in MTBS during 2006. This bay system is characterized by very shallow inner bays with elevated salinity and temperature compared to the rest of the bay area. As a result mainly of the hyper salinity, the inner bay communities are distinct from the outer bay communities. Overall, fairly high species richness with several rare species was observed. High Shannon-Wiener diversity values and ABC plots indicated the healthy status of the polychaete communities, while BOPA index indicated slightly polluted status in 20% of the stations. The oil sensitive amphipods were not completely re-colonized in 20% of the stations, even after 15 years of recovery from the 1991 oil spill.  相似文献   

18.
Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters.  相似文献   

19.
丹江口水库是南水北调中线工程水源地,库湾是水库型湖泊水质安全敏感区,动态调水过程库湾水质直接关系到调水安全.为探究动态调水过程中丹江口水库库湾浮游植物季节变化规律和驱动因子,2018年7月—2019年7月,从丹库入库口到渠首调水口,按季节对18个样点进行水质和浮游植物群落组成分析.从整个丹库来看,浮游植物全年总丰度变化范围为0.43×10~3～4.7× 10~6 cells/L,夏季最高,秋季最低;Shannon-Wiener指数春季最高,秋季最低.春季群落为硅藻—绿藻型,夏季为绿藻—硅藻型,秋季为蓝藻型,冬季为蓝藻—绿藻—硅藻型,秋季蓝藻相对丰度最高.位于丹库准保护区内的库湾胡寨,秋季水体电导率、总氮、总磷和叶绿素a浓度最大,蓝藻丰度最高.从入库口经库湾到调水口,浮游植物群落组成存在明显演替.从水文因子来看,秋季水库水位较高,调水流速和流量增加,线性回归分析表明,水位对ShannonWiener指数的影响最为明显,水位越高则多样性指数越低;流量和流速与Shannon-Wiener指数也呈负相关,但相关性较低.方差分解分析发现,水文因子和理化因子共同影响了浮游植物群落组成;偏Mantel分析显示3个库湾浮游植物群落组成与水温、氧化还原电位、化学需氧量、总氮和总磷浓度相关;典范对应分析也表明,总氮是影响库湾浮游植物群落组成最显著的环境因子.人类干扰活动改变了库湾水质理化性质,强干扰提高了蓝藻门丰度.因此,控制库湾人类干扰强度,尤其在水位和调水量较高的秋季,对于改善水体藻类组成、保护整个丹江口水库水质具有重要意义.  相似文献   

20.
Water Resources - Different types of transboundary water exchange in Russia are considered, including through state, administrative, and natural boundaries. The presented characteristics refer to...  相似文献   

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