Investigation of hydraulics transport time scales within the Arvand River estuary,Iran          下载免费PDF全文

Amir Etemad‐Shahidi  Mostafa Pirnia  Hengameh Moshfeghi  Charles Lemckert 《水文研究》2014,28(25):6006-6015

Transport time scales are key parameters for understanding the hydrodynamic and biochemical processes within estuaries. In this study, the flushing and residence times within the Arvand River estuary have been estimated using a two‐dimensional hydrodynamic model called CE‐QUAL‐W2. The model has been calibrated and verified by two different sets of field data and using the k‐ε vertical eddy diffusivity scheme. Flushing time has been estimated using different methods such as the tidal prism and fraction of freshwater methods. Moreover, residence times have been investigated using pulse residence time, estuarine residence time and remnant function approaches. The results have shown that different methods yield different time scales, and freshwater inflow has the greatest impact upon estimation of residence time, whereas tidal circulation hardly contributes to residence time at all. It has also been shown that the neap‐spring circulation and start phase of simulations have negligible effects on the Arvand's time scales. The investigation of bathymetry showed that two sills of the estuary tend to significantly increase residence time. Understanding the applicability of these time scales and their estimation approaches helps us to evaluate the water quality management of estuaries. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

利用GIS和多维数据库技术实现长江口海域环境时空数据分析     

张勇  翟世奎 《海洋地质与第四纪地质》2009,(2)

基于GIS和多维数据库技术,依据海洋环境数据的特征,建立了长江口及邻近海域海洋环境的时空多维数据模型,研究了海洋环境数据的时空分析方法。依据2003、2004和2006年多航次的现场调查和分析数据,完善了海洋环境时空多维数据模型,对长江口海域环境时空多维海量数据进行了加工处理与可视化分析,并利用ArcGIS软件平台实现了数据的共享与发布,为岸滩蚀退的遏制和河口三角洲环境的综合治理提供了科学的数据基础。  相似文献   

The nitrogen isotopic composition of dissolved nitrate in the Yangtze River (Changjiang) estuary,China     

Xiujuan Liu  Zhiming Yu  Xiuxian Song  Xihua Cao 《Estuarine, Coastal and Shelf Science》2009

The nitrogen isotopic composition of dissolved nitrate (δ¹⁵N-NO₃⁻) in surface water of the Yangtze River estuary was determined in four seasons of 2006. δ¹⁵N-NO₃⁻ ranged from 0.4‰ to 6.5‰ and varied with seasons and geographic regions, reflecting the dynamics of nitrogen cycling in the estuarine ecosystem. δ¹⁵N-NO₃⁻ was markedly lower in February than in other seasons and exhibited conservative mixing, which was probably attributed to the NO₃⁻ being sourced from the atmospheric deposition and agricultural fertilizer. In the upper estuary, the influence of riverine inputs was important during all surveys. In the turbidity maximum zone, nitrification was found with nitrate depleted in ¹⁵N in May, whereas denitrification resulting in heavy δ¹⁵N-NO₃⁻ played an important role in August. More enriched δ¹⁵N-NO₃⁻ values coinciding with losses of nitrate concentrations based on the conservative mixing model were found in the adjacent marine area in May, and may reflect obvious phytoplankton assimilation of dissolved nitrate. In this manner, δ¹⁵N-NO₃⁻ may be a sensitive indicator of nitrogen sources and biogeochemical processing existing in this estuary in conjunction with the variations of dissolved nitrate and other environmental factors.  相似文献   

Surface evolution and carbon sequestration in disturbed and undisturbed wetland soils of the Hunter estuary,southeast Australia   总被引：2，自引：0，他引：2  

A.J. Howe  J.F. Rodríguez  P.M. Saco 《Estuarine, Coastal and Shelf Science》2009

The aim of this work was to quantify the soil carbon storage and sequestration rates of undisturbed natural wetlands and disturbed wetlands subject to restriction of tidal flow and subsequent rehabilitation in an Australian estuary. Disturbed and undisturbed estuarine wetlands of the Hunter estuary, New South Wales, Australia were selected as the study sites for this research. Vertical accretion rates of estuarine substrates were combined with soil carbon concentrations and bulk densities to determine the carbon store and carbon sequestration rates of the substrates tested. Relationships between estuary water level, soil evolution and vertical accretion were also examined. The carbon sequestration rate of undisturbed wetlands was lower (15% for mangrove and 55% for saltmarsh) than disturbed wetlands, but the carbon store was higher (65% for mangrove and 60% for saltmarsh). The increased carbon sequestration rate of the disturbed wetlands was driven by substantially higher rates of vertical accretion (95% for mangrove and 345% for saltmarsh). Estuarine wetland carbon stores were estimated at 700–1000 Gg C for the Hunter estuary and 3900–5600 Gg C for New South Wales. Vertical accretion and carbon sequestration rates of estuarine wetlands in the Hunter are at the lower end of the range reported in the literature. The comparatively high carbon sequestration rates reported for the disturbed wetlands in this study indicate that wetland rehabilitation has positive benefits for regulation of atmospheric carbon concentrations, in addition to more broadly accepted ecosystem services.  相似文献   

广西廉州湾和三娘湾表层水体中多环芳烃的时空分布与来源解析     

王伟权  张瑞杰  余克服  王英辉  潘长桂  曾维斌 《热带地理》2019,39(3):337-346

以16种优控多环芳烃（PAHs）为研究对象，分别于2017年夏季（8月）和冬季（12月）采集广西廉州湾和三娘湾的河口和海岸带14个站位的表层海水样品，利用固相萃取、气相色谱-质谱联用仪对其进行分析，探讨其时空分布、组成和来源，并评价其生态风险。结果表明：廉州湾和三娘湾河口及海岸带水体中多环芳烃单体的平均质量浓度总体上与其溶解度和极性呈正相关关系，即以2~3环芳烃为主，4~6环芳烃检出率和质量浓度均较低。PAHs总质量浓度（∑16PAHs）在夏季河口水体（72.71 ng/L）明显高于海岸带水体（56.28 ng/L）（t检验，p＜0.01），冬季河口（106.67 ng/L）与海岸带（92.43 ng/L）差异不显著（t检验，p＞0.05）。冬季河口和海岸带PAHs质量浓度均明显高于夏季。大风江和南流江PAHs的入海通量达525.3 kg/a，夏秋季占85%以上，反映了雨季河流对海岸带具有明显的影响。南流江PAHs入海通量占2条河流总量的87%以上，对廉州湾和三娘湾的影响最大。运用同分异构体比值和主成分分析方法对海水中PAHs进行来源解析，结果表明：夏季主要为燃烧源和石油源的混合来源，冬季主要为燃烧源。与其他国家或地区相比，廉州湾和三娘湾海水中PAHs质量浓度处于较低水平。生态风险评价结果显示廉州湾和三娘湾表层海水中的PAH风险较小。  相似文献   

渤海3个河口区底栖硅藻群落的时空变化特征   总被引：1，自引：0，他引：1  

王珊珊  刘东艳  王玉珏  袁子能 《海洋学报》2020,42(8):101-114

底栖硅藻是河口泥滩系统中的重要初级生产者，其群落结构的时空变化可显著影响到河口底栖动物生产力。本研究选取渤海区域的大辽河口、汉沽河口和黄河口为研究对象，分析了泥滩中底栖硅藻群落结构的季节变化特征(2014?2016年)与空间差异，并探讨了环境因素的影响作用。结果表明，3个河口区底栖硅藻多样性和生物量高峰均出现在秋季，优势种存在显著季节演替特征；在空间上，大辽河口和汉沽河口的底栖硅藻生物量显著高于黄河口。底栖硅藻群落结构与多种环境因子的相关性分析表明，温度和营养盐浓度变化对底栖硅藻群落的季节性特征影响显著；河口沉积物的粒径、潮差与径流量可能是造成底栖硅藻群落空间差异的重要因素，黄河口较低的底栖硅藻生物量显著受限于较粗的沉积物粒径和显著的磷限制。  相似文献   

A siltation simulation and desiltation measurement study downstream of the Suzhou Creek Sluice,China     

季永兴  杨绯  张汉云  卢永金 《中国海洋工程》2013,27(6):781-793

The Suzhou Creek Sluice is currently the largest underwater plain gate in the world, with a single span of 100 m. It is located in a tidal estuary at the junction of the Huangpu River and Suzhou Creek in Shanghai, China. In this study, physical and 2D vertical mathematical models were used to investigate and distinguish the mechanism of siltation downstream of an underwater plain gate from that of other gates types. According to quantitative data obtained by site investigation and the application of the physical hydrodynamic models, it was found that the characteristics of the tidal estuary as well as the fact that the sluice span is equal to the creek width are the major reasons contributing to siltation. A possible desiltation treatment system is proposed for the underwater plain gate. The system includes selection of a suitable location that allows the determination of a reasonable top elevation of the sluice floor, reserving sufficient space under the gate to accommodate siltation, setting up a mechanical desiltation system, and flushing silt along with overflow over the top of the gate. Furthermore, on-site hydraulic silt flushing experiments and a topography survey were conducted. These results showed that the measurement system is effective, and by maintaining this scheduled operation once a month, the downstream riverbed has been maintained in a good condition.  相似文献   

Artificial mouth opening fosters anoxic conditions that kill small estuarine fish     

Alistair Becker  Laurie J.B. Laurenson  Kylie Bishop   《Estuarine, Coastal and Shelf Science》2009,82(4):566-572

Fish kills are not uncommon within estuaries in many regions of the world. In seasonally open systems, which are common in temperate areas, they are often associated with mouth openings. Such a kill occurred in July 2005 in the Surrey Estuary following a closed mouth period of seven months resulting in the loss of many thousands of fish. At the time the fish community within the estuary was under investigation which provided comprehensive data of this population prior to the kill. Monthly water quality monitoring was also being conducted prior to the kill and also carried out on a daily basis following the mouth opening. The Surrey was stratified during the closed mouth phase, isolated waters below the halocline had stagnated and become anoxic. As a result only waters above the halocline contained oxygen concentrations capable of sustaining most fish. It appears that if a mouth opening happens under low flow conditions, a shearing effect occurs within the water column where surface waters flow out to sea leaving deeper waters behind. This resulted in only anoxic waters being present for in excess of six days and was responsible for the fish kill. Fish sampling of the Surrey Estuary was conducted three and six months following the kill and those data were compared to that collected in the 12 months prior to the event. Three months after the kill few fish were collected within the estuary and included marine opportunists near the mouth and estuarine resident species in the far upper reaches of the system. However six months following the kill large numbers of estuarine resident species were collected throughout the Surrey Estuary. As many species were euryhaline, it is believed that some individuals migrated into freshwater reaches of the Surrey to escape the anoxic conditions within the estuary. As conditions improved they recolonised the Surrey Estuary. The high fecundity and rapid growth of these small, short lived species probably aided in their re-establishing populations within the estuary. It is clear from this research that artificial openings of estuaries should be avoided during low flow periods when oxygen concentrations are low. It also appears that many of the small estuarine resident species common in seasonally open estuaries are capable of recolonising estuaries following fish kills. The effects on larger, longer lived resident species are not known but likely to be more detrimental due to longer time required for them to reach sexual maturity.  相似文献   

Feeding ecology and ontogenic diet shifts of juvenile fish species in an inverse estuary: The Sine-Saloum,Senegal     

Ndombour Gning  Guy Vidy  Omar Thiom Thiaw 《Estuarine, Coastal and Shelf Science》2008

We examined the diet of juvenile fish of four species – Eucinostomus melanopterus (Gerreidae), Ethmalosa fimbriata (Clupeidae), Monodactylus sebae (Monodactylidae), and Sarotherodon melanotheron (Cichlidae) – between their appearance on the nursery ground and the end of the recruitment season, when they began to shift to deeper parts of the estuary. Fish were collected from the Sine-Saloum, an inverse estuary in Senegal, West Africa. Sampling was conducted at six sites located along the salinity gradient. The study was conducted in the context of an inverse estuary where increasing salinity leads to the disappearance of mangroves.  相似文献   

Influence of halophytes and metal contamination on salt marsh macro-benthic communities     

C. Vinagre  H.N. Cabral  I. Caador 《Estuarine, Coastal and Shelf Science》2008,76(4):715-722

Since an important fraction of the organic matter produced by salt marshes is decomposed in situ, macro-benthic communities are particularly exposed to the trace metals retained by these systems. Yet, few studies have investigated the macro-benthic communities using the between-root sediment habitat of the salt marsh halophytes (salt-tolerant plants), or the effect of trace metal pollution on its population dynamics. In the present study, samples were collected in vegetated and unvegetated sediment, in three salt marshes in the Tagus estuary, for trace metal concentration determination in the sediment and in the halophytes roots, grain size determination and macro-benthic organism identification. Data analysis revealed that the distribution of macro-benthic organisms is mainly determined by metal contamination, metal type and by the presence/absence of halophytes, not by the halophyte species. Five different associations were identified: resistant organisms were associated with the highest concentrations of lead (sediment); tolerant organisms with zinc, copper (sediment and roots) and lead (roots); cadmium in the sediment with a lack of macro-benthic life; sensitive organisms with low levels of metals except for cadmium in the roots; and macro-benthos typical of intertidal mudflats with unvegetated areas with low metal contamination.  相似文献