Estuary mouth

The term mouth is recommended to be used either in a wide sense as a reduced version and absolute synonym if the term mouth area (in this case, the use of the term river mouth is quite necessary) or in a narrow sense as applied to the point of inflow of any watercourse to another watercourse (tributary mouth) or to a receiving basin (delta branch mouth) as well as to the outlet to the open sea from a semi-enclosed coastal water body (liman mouth, lagoon mouth, estuary mouth). 

Figure 9 Relationship between estuarine turbidity in NTU and distance from the mouth of St. Lucia Estuary, Natal, on a rising tide on 20 March 1981, showing a clear turbidity maximum 8-12 km from the estuary mouth for both near-bed (bottom) and surface (top) waters. (From Cyrus DP (1988) Turbidity and other physical factors in Natal estuarine systems. Part 1 selected estuaries. Journal of the Limnological Society of southern Africa 14(2) 60-71.)...

Although the technology required to harness tidal energy is well established, because tidal power is expensive there is only one major tidal generating station in operation in the world today. This is a 240-megawatt power plant at the mouth of the La Ranee River estuary on the northern coast of France, generating power roughly equal to the annual consumption of the nearby town of Rennes, which has a population of 200,000. 

Several studies have examined the partitioning of U on particles and colloids. Results from detailed sampling and particle separation in the Amazon estuary shows that most of the uranium at the Amazon River mouth is associated with particles (>0.4 im) and that >90% of the uranium in filtered water (<0.4 im) is transported in a colloidal phases (from a nominal molecular weight of 10 000 MW up to 0.4 im) (Swarzenski et al. 1995 Moore et al. 1996). Mixing diagrams for uranium in different size fractions in the Amazon estuary reveal that uranium in all size fractions clearly display both removal and substantial input during mixing. 

Figure 4. The uranium concentration in unfiltered water, 0.2 gm and 3 kD filtered water in river water from the Kalix River mouth and samples from the low salinity estuarine zone (0-3). Data plotted against conductivity (although the salinity scale is not defined below 2, a tentative scale is indicated). The lines represent the best fit for each fraction in the estuary. The data from the Kalix river mouth represent the river water component, which show <10% aimual variation in concentration. The analytical errors are smaller than the symbols. Data from Andersson et al. (2001). Copyright 2001 Elsevier Science.

Figure 5. The in 0.2pm and 3 kD filtered water and colloids phase (3kD - 0.2pm) and particles (>0.2 pm) as well as material from sediment traps plotted versus conductivity in the low salinity zone (0-3) of the Kalix River estuary. The stippled area marks the reported annual range in at the Kalix river mouth, which show a substantial variation compared to the uranium concentration. Data from Andersson et al. (2001). Copyright 2001 Elsevier Science.

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

The solubility of chlordecone in water is low (1--3 mg/L) and as with mirex, contamination is more likely to be associated with the particulate matter in the water rather than the water itself. Chlordecone was detected primarily in water samples collected in and around the production facility site in Hopewell, Virginia, and in adjacent waters of the James River estuary. Effluent from the Life Sciences Products Company facility contained 0.1 —1.0 mg/L (ppm) chlordecone, while water in holding ponds at the site contained 2--3 mg/L (ppm) chlordecone (Epstein 1978). Levels of chlordecone in river water in August 1975 ranged from not detectable (<50 ng/L [ppt]) in the York River and Swift Creek areas, to levels of 1--4 pg/L (ppb) in Bailey Creek which received direct effluent discharges from the Hopewell Sewage Treatment Plant. Water concentrations of up to 0.3 p g/L (ppb) were detected in the James River at the mouth of Bailey Creek and in the Appomattox... 

Sill Shallow portion of the seafloor that partially restricts water flow, usually at the mouth of a marginal sea or estuary. 

The Suwannee River was sampled at its origin at the outlet of the Okefenokee Swamp. This fulvic acid, therefore, is likely to be less degraded than a sample from the Calcasieu River that was taken near its mouth on the estuary during a warm, low-flow period in early summer. Metal-ion solubility controls and sorption on mineral surfaces in upland soils also might fractionate the fulvic acid in the Calcasieu River. In contrast, the Suwannee River mineral-soil solubility controls are less significant. 

Given such large inputs (even though their exact values must be subject to considerable variation and uncertainly), it is important to determine how much of the nutrients and other materials which enter an estuary pass through to the coastal ocean. Since it is extremely difficult to obtain direct measurements of the net transport of dissolved or particulate substances at the mouth of the estuary, the most promising... 

In their studies of metals in Chesapeake Bay, however, Bieri et al. (1982) claim that more than 60 % of both the Pb and Mn input is retained in the bed sediments. In their recent studies of heavy metals in Delaware Bay (USA), Church, Tramontano and Murray (1984 and later personal communication) calculated retention of 92 % of the Mn, 37% of the Cu and 32 % of the Cd input to that estuary. However, losses from the estuary in that analysis were based on calculations of the probable flux out of the mouth of the Bay using a layered flow model. When sediment concentrations and accumulation rates were used, only small amounts of Mn and Cd appeared to be retained in the system (Church, personal communication). At this point we are not aware of any convincing evidence that clearly contradicts the findings regarding the behavior of Pb, Cu,Mn or Cd in Narragansett Bay. Unfortunately, the number of mass balances for these elements is so small that this is not a particularly reassuring claim. 

Water samples from large rivers, estuaries, and the sea can be collected in using flasks that are hand-held (polyethylene-gloved hand, mouth down) or attached to a 3-4 m telescopic tube, from platforms with the aid of a pump, and from oar-propelled rubber dinghies, and also with special bottles for discrete depth sampling (Figure 1.7). 

Eutrophication Processes in Coastal Systems Origin and Succession of Plankton Blooms and Effects on Secondary Production in Gulf Coast Estuaries, Robert J. Livingston Handbook of Marine Mineral Deposits, David S. Cronan Handbook for Restoring Tidal Wetlands, Joy B. Zedler Intertidal Deposits River Mouths, Tidal Flats, and Coastal Lagoons, Doeke Eisma... 

Estuary Region of interaction between rivers and near-shore ocean waters, where tidal action and river flow mix fresh and salt water. Such areas include bays, mouths of rivers, salt marshes, and lagoons. These brackish water ecosystems shelter and feed marine life, birds, and wildlife. 

Figure 1.2 Classic estuarine zonation depicted from the head region, where fluvial processes dominate, to the mid- and mouth regions where tidal and wave processes are the dominant controlling physical forces, respectively. Differences in the intensity and sources of physical forcing throughout the estuary also result in the formation of distinct sediment facies. (Modified from Dalrymple et al., 1992, with permission.)...

River-dominated estuaries are formed in high river discharge regions where the valley is presently not drowned by the sea. The two subcategories are as follows (a) tidal river estuaries are associated with large rivers systems that are influenced by tidal action with the salt front usually not well developed at the mouth (b) delta-front estuaries are found in sections of deltas that are affected by tidal action and/or salt intrusion. 

Figure 2.7 Sedimentary facies in three general zones of the Ogeechee River/Ossabaw Sound estuary (USA). Fine-grained sediments predominate in the lower-energy region (stations 2, 3, and 4) as opposed to the high-energy point bars (station 5) and mouth (1) which have a higher abundance of coarse-grained sediments. (Modified from Howard et al., 1975.)...

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