河口冲刷时间的研究进展与问题     

王世俊  李春初  唐兆民 《台湾海峡》2004,23(1):116-122

冲刷时间是表征河口水体交换的一个非常重要的物理量．本文在回顾潮汐河口冲刷时间研究现状的基础上，分析了影响冲刷时间的主要影响因子．结论表明冲刷时间不仅是潮棱体和淡水径流量的函数，而且与河口形态、天气要素密切相关，各要素之间的非线性关系更增加了冲刷时间研究的复杂性．在今后的研究中，应以河口界面的观点，加强河口冲刷时间界面机制的研究，并注重人类活动对冲刷时间的影响．  相似文献   

The nutrient and trace metal geochemistry of a dredge plume     

John M. Tramontano  W.F. Bohlen 《Estuarine, Coastal and Shelf Science》1984,18(4):385-401

Field sampling of the dissolved and particulate material field downstream of a large volume bucket dredge operating in the lower Thames River estuary near New London, Connecticut, was conducted in order to examine the magnitude and character of the dredge-induced resuspension. These data indicate that large amounts of dissolved phosphate, ammonia, silica, manganese, copper and particulate materials are released into the water column, whereas cadmium concentrations were unaffected. Concentrations in the vicinity of the dredge exceed background levels by two to nine times for the dissolved materials and by two orders of magnitude for particulates. During the ebb cycle, downstream material concentrations decrease rapidly to background within approximately 180 m for dissolved materials and 700 m for particulates.Two mechanisms were found to control the distribution of materials downstream of the dredge: (a) physical transport, including advection, turbulent mixing and diffusion, and (b) geochemical processes (i.e. adsorption, desorption, precipitation, dissolution, etc.). The concentration of dissolved materials downstream of the dredge decrease at a first order exponential rate. The downstream distribution of the dissolved ammonia and silica was found to be consistent with the reactivity experiments (Figure 8) which predicted that PO₄ would undergo a decay in concentration in the presence of suspended sediments. Absorption of phosphate onto suspended sediments and gravitational settling of the suspended particulates were the processes. Manganese and copper underwent a dual transformation which involved an initial dissolution, followed by flocculation and possible coprecipitation as MnO₂. Cadmium concentrations in the water column were unaffected by the dredging process due to low pore water concentrations.The observed spatial distribution indicates that dredge-induced injection of dissolved and particulate materials is primarily a near field phenomenon producing relatively minor variations as compared to those caused by naturally occurring storm events. These latter systems have been shown (Tramontano, 1978; Bohlen et al., 1979) to produce estuary-wide variations in suspended materials, PO₄ and NH₄ concentrations increasing the mass of materials in suspension by at least a factor of two. This increase in total suspended load, PO₄ and NH₄, is nearly an order of magnitude larger than that produced by the dredge.  相似文献   

Occurrence and Activity of Lipolytic Bacterioneuston and Bacterioplankton in the Estuarine Lake Gardno     

Z. J. Mudryk  P. Skrczewski 《Estuarine, Coastal and Shelf Science》2000,51(6):763

The number and lipolytic activity of neustonic and planktonic bacteria inhabiting estuarine Lake Gardno were determined. Lipolytic bacteria were very numerous in investigated layers of water, accounting for 10–88% of the total number of culturable heterotrophic bacteria. Significant differences were found in the decomposition of individual lipid substrates by bacteria. The highest percentage of neustonic and planktonic strains were able to hydrolyse tributyrin and Tween 85. The least numerous bacteria group was microflora hydrolysing Tween 20 and Tween 40. The activity of lipases synthesized by bacteria from the subsurface layer was higher than that of lipases produced by bacteria isolated from the surface layers. A significant effect of salinity on the activity of lipases has been shown.  相似文献   

Columbia Bay, Alaska: an ‘upside down’ estuary     

Roy A. Walters  E. G. Josberger  C. L. Driedger 《Estuarine, Coastal and Shelf Science》1988,26(6)

Circulation and water properties within Columbia Bay, Alaska, are dominated by the effects of Columbia Glacier at the head of the Bay. The basin between the glacier terminus and the terminal moraine (sill depth of about 22 m) responds as an ‘upside down’ estuary with the subglacial discharge of freshwater entering at the bottom of the basin. The intense vertical mixing caused by the bouyant plume of freshwater creates a homogeneous water mass that exchanges with the far-field water through either a two- or a three-layer flow. In general, the glacier acts as a large heat sink and creates a water mass which is cooler than that in fjords without tidewater glaciers. The predicted retreat of Columbia Glacier would create a 40 km long fjord that has characteristics in common with other fjords in Prince William Sound.  相似文献   

A study into the export of saline water from Hervey Bay, Australia   总被引：2，自引：0，他引：2  

Joachim Ribbe 《Estuarine, Coastal and Shelf Science》2006,66(3-4):550-558

Australia's climate is one of the world's driest and locally characterised by high year-to-year rainfall variability. Due to high evaporation and low river runoff many estuaries and embayments in the region are characterised by inverse conditions with salinity increasing toward the coast and river mouths. Such conditions were also found during the first comprehensive hydrographic survey of Hervey Bay located at the east coast of Australia in early spring 2004. The survey traced a subsurface salinity maximum that was found in earlier studies within the East Australia Current, east of Hervey Bay to the shallow southwest regions of the bay. These are identified as the most likely source region for locally produced saline Hervey Bay Water. Utilising a simple box model, mean evaporation rates and historical river runoff data, it is demonstrated that inverse conditions are likely to dominate throughout the year. The negative circulation is a climatological feature of this estuary that is not limited to the dry season of the year. Due to persistent drought and declining rainfall in coastal eastern Australia, these conditions are likely to persist into the near future and need to be considered in coastal management strategies.  相似文献   

Nutrient flux in the Rhode River: Tidal exchange of nutrients by brackish marshes     

Thomas E. Jordan  David L. Correll  Dennis F. Whigham 《Estuarine, Coastal and Shelf Science》1983,17(6):651-667

Tidal exchanges of nitrogen, phosphorus, and organic carbon by a high and a low elevation marsh in the Rhode River estuary were measured throughout the year. Both marshes tended to import particulate matter and export dissolved matter, although they differed in the fluxes of certain nutrients. Compared with tidal exchanges, bulk precipitation was a major source of ammonia and nitrate and a minor source of other nutrients. There was a net retention of nutrients by the portion of the Rhode River that included both marshes and a mudflat. However, the marshes accounted for only 10% of the phosphorus retention and 1% of the nitrogen retention while they released organic carbon amounting to 20% of the retention. This suggests that the mudflat acted as a sink for nutrients. The primary role of the marshes seems to be transformation of particulate to dissolved nutrients rather than nutrient retention or release.  相似文献   

Behaviour of colloidal trace metals (Cu, Pb and Cd) in estuarine waters: An approach using frontal ultrafiltration (UF) and stripping chronopotentiometric methods (SCP)     

Matthieu Waeles  Virginie Tanguy  Gaëtane Lespes  Ricardo D. Riso 《Estuarine, Coastal and Shelf Science》2008,80(4):538-544

The frontal cascade ultrafiltration (UF) technique in conjunction with stripping chronopotentiometry (SCP) has been evaluated for determining the colloidal distribution of Cu, Pb and Cd in estuarine waters. Metallic concentrations in seven size fractions (0.45 μm–0.22 μm; 0.22 μm–300 kDa; 300–50 kDa; 50–30 kDa; 30–10 kDa; 10–5 kDa; <5 kDa) were determined with the aim to investigate their changes along the salinity gradient of the Penzé system (NW France). These data, completed by analysis of the total dissolved metals at 10 stations over the whole freshwater–seawater mixing zone, provided some insights in the removal and addition processes that affect Cu, Pb and Cd in estuaries.  相似文献   

Habitat changes in coastal wetlands associated to hydrological changes in the watershed     

M.F. Carreño  M.A. Esteve  J. MartinezJ.A. Palazón  M.T. Pardo 《Estuarine, Coastal and Shelf Science》2008

In recent decades wetlands associated with the Mar Menor lagoon (SE Spain) have undergone several hydrological and biological changes as a consequence of increased water inputs from agricultural drainage off the watershed. Changes in the vegetal communities were studied by means of supervised classification of Landsat images, and TM and ETM+ sensors during the period 1984–2000, and a series of land cover maps was created. Changes in the wetland area during this period were analysed and a good fit was found with the total area of irrigated lands in the watershed. The series of land cover maps also allowed the study of the internal composition of the vegetal communities in each wetland. Important changes were detected, with an expansion of reedbeds and a significant reduction in the area occupied by priority habitats according to the Habitats Directive.  相似文献   

Dynamics of evapotranspiration from a riparian pond complex in the Western Boreal Forest,Alberta, Canada     

R. M. Petrone  U. Silins  K. J. Devito 《水文研究》2007,21(11):1391-1401

The relative contributions to total actual evapotranspiration (AET) from pond and riparian areas in a pond‐wetland complex in the Western Boreal Plain (WBP) of northern Alberta are measured using the Bowen ratio energy balance technique. Measurements show that a pond typical of the WBP evaporates at a rate more than twice that of the adjacent riparian peatland. Relating the actual to potential evapotranspiration over both surfaces yields Priestley–Taylor α coefficients of 0·69 and 1·11 for the peatland and pond respectively. Further results demonstrate that the sheltering and turbulent influences of the adjacent forested areas must be considered in the processes governing the permanence of WBP ponds. That is, forestry practices may inadvertently enhance the evaporative losses from the ponds, over and above the controls exerted by the regional climate. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

黄河三角洲滨海湿地健康条件评价概念模型   总被引：3，自引：0，他引：3  

叶思源  SMITH Gregory Jame  高茂生  丁喜桂  刘强 《地质论评》2009,55(4):545-551

滨海湿地健康与生物学特征主要取决于区域上的水文与盐度体制以及景观尺度上的土地利用现状。然而,由于滨海湿地条件评价的指标和标准并不十分清楚,因此,对滨海湿地系统条件进行评价,目前仍是环境科学的难点。中国地质调查局（CGS）青岛海洋地质研究所与美国地质调查局湿地研究中心合作先后为美国密西西比河下游生态环境及中国黄河三角洲（YRD）滨海湿地评价建立了概念模型。本文将陈述YRD湿地评价的概念模型。此模型的建立在于确定滨海湿地当前的条件和随时间改善或退化的过程,以及确定优先管理的区域。CGS项目之所以选取YRD作为滨海湿地的研究对象主要是因为它具有重要的生态意义。由于上游来水减少或黄河断流,该区湿地生境十分脆弱。本文提出此概念模型可为今后湿地条件评价指标确定、调查研究活动和数据采集提供指导。通过该模型的构建,使环境变化可用具体指标来度量,从而服务于滨海湿地生态系统的保护与管理活动。  相似文献