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1.
Tidal variability in the water quality of an urbanized estuary 总被引:1,自引:0,他引:1
Tide and water quality data were collected concurrently in the Hackensack River estuary (HRE), a tidal tributary of the New
York-new Jersey Harbor estuary. Harmonic analyses of tidal elevation data indicate that HRE tides are predominantly semidiurnal,
though modulated by diurnal and fortnightly components. Nearly uniform tidal ranges (averaging approximately 1.6 m) were observed
at three stations within the HRE. Periodogram estimates reveal significant tidal variability for the water quality parameter
NH4−N under dry-weather conditions. Lag correlation analyses associate NH4−N concentration variations with water level fluctuations. Longitudinal profile plots for NH4−N reveal a consistent pattern of tidal translations, with peak concentrations oscillating about a major wastewater discharger.
These analyses suggest that the distribution of NH4−N concentrations in the HRE is controlled primarily by major point source loadings and horizontal advection. A simplified,
one-dimensional model is used to describe this distribution. Effects of tidal variability in masking water quality status
and waak trends are also analyzed. These analyses highlight the potential importance of short-term water quality variability
in tidal estuaries where concentration gradients are large. 相似文献
2.
The flooding-drying process over the intertidal zone of the Satilla River estuary of Georgia was examined using a three-dimensional
(3-D) primitive equations numerical model with Mellor and Yamada's (1982) level 2.5 turbulent closure scheme. The model was
forced by the semi-diurnal M2, S2, and N2 tides and freshwater discharge at the upstream end of the estuary. The intertidal salt marsh was treated using a 3-D wet-dry
point treatment technique that was developed for the σ-coordinate transformation estuary model. Good agreement was found between
model-data comparison at anchor monitoring sites and also along the estuary that suggested that the model provided a reasonable
simulation of the temporal and spatial distribution of the 3-D tidal current and salinity in the Satilla River estuary. Numerical
experiments have shown that the flooding-drying process plays a key role in the simulation of tidal currents in the main river
channel and in water transport over the estuarine-salt marsh complex. Ignoring this process could lead to a 50% under-estimation
of the amplitude of tidal currents. The model results also revealed a complex spatial structure of the residual flow in the
main channel of the river, with characteristics of multiple eddy-like cell circulations. These complicated residual currents
are formed due to tidal rectification over variable topography with superimposition of inertial effects, asymmetry of tidal
currents, and baroclinic pressure gradients. Water exchanges over the estuary-intertidal salt marsh complex are asymmetric
across the estuary, and tend to vary periodically on the northern side while quickly washing out of the marsh zone on the
southern side. Strong Stokes’ drifting velocity was predicted in the estuary, so that the Lagrangian trajectories of particles
were characterized by strong nonlinear processes that differ significantly from those estimated by the Eulerian residual currents. 相似文献
3.
R. Verney J.-C. Brun-Cottan R. Lafite J. Deloffre J. A. Taylor 《Estuaries and Coasts》2006,29(4):653-664
Tidal currents and the spatial variability of tidally-induced shear stress were studied during a tidal cycle on four intertidal
mudflats from the fluvial to the marine part of the Seine estuary. Measurements were carried out during low water discharge
(<400 m3 s−1) in neap and spring tide conditions. Turbulent kinetic energy, covariance, and logarithmic profile methods were used and
compared for the determination of shear stress. The cTKE coefficient value of 0.19 cited in the literature was confirmed. Shear stress values were shown to decrease above mudflats
from the mouth to the fluvial part of the estuary due to dissipation of the tidal energy, from 1 to 0.2 N m−2 for spring tides and 0.8 to 0.05 N m−2 for neap tides. Flood currents dominate tidally-induced shear stress in the marine and lower fluvial estuary during neap
and spring tides and in the upper fluvial part during spring tides. Ebb currents control tidally-induced shear stress in the
upper fluvial part of the estuary during neap tides. These results revealed a linear relationship between friction velocities
and current velocities. Bed roughness length values were calculated from the empirical relationship given by Mitchener and
Torfs (1996) for each site; these values are in agreement with the modes of the sediment particle-size distribution. The influence
of tidal currents on the mudflat dynamics of the Seine estuary was examined by comparing the tidally-induced bed shear stress
and the critical erosion shear stress estimated from bed sediment properties. Bed sediment resuspension induced by tidal currents
was shown to occur only in the lower part of the estuary. 相似文献
4.
Sediment transport and trapping in the Hudson River estuary 总被引:3,自引:0,他引:3
The Hudson River estuary has a pronounced turbidity maximum zone, in which rapid, short-term deposition of sediment occurs during and following the spring freshet. Water-column measurements of currents and suspended sediment were performed during the spring of 1999 to determine the rate and mechanisms of sediment transport and trapping in the estuary. The net convergence of sediment in the lower estuary was approximately 300,000 tons, consistent with an estimate based on sediment cores. The major input of sediment from the watershed occurred during the spring freshet, as expected. Unexpected, however, was that an even larger quantity of sediment was transported landward into the estuary during the 3-mo observation period. The landward movement was largely accomplished by tidal pumping (i.e., the correlation between concentration and velocity at tidal frequencies) during spring tides, when the concentrations were 5 to 10 times higher than during neap tides. The landward flux is not consistent with the long-term sediment budget, which requires a seaward flux at the mouth to account for the excess input from the watershed relative to net accumulation. The anomalous, landward transport in 1999 occurred in part because the freshet was relatively weak, and the freshet occurred during neapetides when sediment resuspension was minimal. An extreme freshet occurred during 1998, which may have provided a repository of sediment just seaward of the mouth that re-entered the estuary in 1999. The amplitude of the spring freshet and its timing with respect to the spring-neap cycle cause large interannual variations in estuarine sediment flux. These variations can result in the remobilization of previously deposited sediment, the mass of which may exceed the annual inputs from the watershed. 相似文献
5.
David A. Brock 《Estuaries and Coasts》2001,24(4):509-521
Nueces Estuary is a relatively shallow, microtidal estuary which receives inputs from a significant industrial and urban area and from a semi-arid drainage basin. Nitrogen (N) loadings were compiled using FLUX model and flow x concentration calculations for four annual periods spanning a range of inflow volumes. For each annual period, N budgets were developed, supported by water and total dissolved solids dudgets. Budget compilations include materials transported in tidal exchange with the Gulf of Mexico and with neighboring bays. Wastewater discharge contributes twice as much N to the bay than inflows from the Nueces River. Net flows and tidal entrainment of materials from neighboring bays contribute 24–32% of total loadings except during flood flows of the Nueces River. Atmospheric deposition to the estuary surface provides 8% of N loading. Despite low tidal amplitude and a restricted Gulf pass tidal entrainment losses are the main vehicle of export, except during flood flows, when net flows to the Gulf become important. The system exports much more of its total N load than would be expected from its water residence time, possibly facilitated by ship channel longitudinal transport. Denitrification accounts for 30–40% of all N lost. Uncertainties in components of the budget are estimated and included in compilations of confidence bounds for N budget components. 相似文献
6.
The estuary of Odiel and Tinto rivers, located on the southwestern coast of the Iberian Peninsula, receives acidic fluvial
water discharges with high concentrations of sulphates and heavy metals from these rivers. In addition, a big industrial complex
which efflues directly on the system is located in the same estuary. The effluents induce the presence in the estuary of high
concentrations of heavy metals and phospates (nutrients). The application of factorial analysis techniques on the nutrients
and heavy metal concentrations in 46 water samples taken from 32 different sampling stations located along the estuary, allows
three groups of elements and compounds with a distinct origin to be determinated. So, Cu and Zn have a clear fluvial provenance,
whereas PO4 and As are clearly industrial wastes and Cl, K, Ca, Li, Rb and Sr come from the sea. From the factorial analyses we can deduce
the existence of two agents controlling the behavior of the analyzed elements, which are: the tidal exchange with the open
sea and the fluvial supply.
Received: 20 November 1998 · Accepted: 11 August 1999 相似文献
7.
We describe the tidal circulation of a coastal plain estuary across a flood tide delta located at its entrance. The area connects
the downstream portion of the main estuary extending 30–40 km inland to the more complex delta reach that consists of a shallow
main channel and a series of smaller side channels. The delta acts as a frictionally dominated zone that modifies the tidal
wave from a simple sinusoid to one with ebb currents that accelerate to maximum early in the tidal cycle and last more than
one-half of the tidal cycle. Along smaller side channels, the tidal currents favor stronger flood or ebb currents, depending
upon the local surrounding morphology. The phase difference between ebb currents in the small channels relative to those in
the main channel cause some of the salt to be retained thus reducing the tendency of freshwater discharge to flush salt out
of the system. This mechanism of retention differs from the selective withdrawal mechanism described for this estuary in Blanton
et al. (2000). 相似文献
8.
In the lower delta of the Paraná River, at the head of the Río de la Plata estuary (Argentina), we compared net aboveground
primary production (NAPP) and soil properties of the dominant macrophyteScirpus giganteus (Kunth) in a floating and an attached marsh community. Both marshes are tidally influenced but in different ways. The floating
marsh site is relatively isolated from tidal influences because its ability to float makes it resistant to overland flow and
to sediment inputs from the estuary. The attached marsh lacks the capacity to float and receives sediment supplies from the
estuary through overland flow. These hydrologic differences are reflected in lower mineral content in sediments of the floating
marsh. Using a leaf tagging technique, estimated NAPP was 1,109 ± 206 g m−2 yr−1 for the floating marsh and 1,866 ±258 g m−2 yr−1 for the attached marsh. We attribute the lower NAPP of the floating marsh to isolation from sediment input from overland
flow. 相似文献
9.
The Odiel-Tinto estuary is one of the most significant estuarine systems along the mesotidal Huelva Coast. The dynamics of this coastal sector are controlled by the interaction of ebb-tidal currents and the prevailing southwesterly waves. The main sediment supply is provided by an intensive west-to-east longshore current, transporting sand from Portuguese cliffs and discharge from the River Guadiana. The tidal range is mesotidal (2.0 m) and the mean significant wave height is 0.6 m with an average period of 3.6 s. This estuary mouth comprises three different barriers separated by the main estuary channel, and another marginal one that drains a significant part of the system. Saltés Island can be found between these two channels, which is composed of sandy barriers separated by muddy salt marshes that form a protected natural park. East of the main channel is Mazagón Beach, one of the most important tourist resorts on this coast. Recent papers have demonstrated that Saltés Island evolved as a chenier plain over the last 3000 years. The cause of this evolution was a special wave refraction scheme caused by two ebb-tidal delta systems located at the end of the two tidal channels. Three important harbour infrastructures have been constructed at the estuary mouth: a) a jetty at the end of Saltés Island, finished in 1977; b) a second and shorter jetty bordering the marginal channel constructed in 1984, and; c) a dock for sailing activities built on Mazagón Beach. These three structures have modified the natural dynamic scheme. The first consequence was to inhibit the functioning of the chenier plain, affecting the natural environment; the second was to intensively erode Mazagón Beach, endangering this tourist site.This paper analyses the causal relationships that exist between the harbour infrastructures and the resultant modifications. 相似文献
10.
河口地区感潮河段水动力过程复杂,为在突发水污染事故中合理制定精细化应急方案,基于环境流体水动力模型(EFDC)从水动力学角度对不同水文条件下深圳河口水域突发水污染事故的影响范围、时间及程度进行了数值模拟分析,提出了一种判断河口海湾地区主导水动力因素的分析方法。采用基于傅里叶变换的频谱分析法对事故中污染物输移扩散的主要影响因子进行了准确识别,并采用单因变量多因素方差分析法进行了印证。结果表明,潮流是感潮河段水动力过程的主要驱动因素,但在突发水污染事故中,深圳河各断面特征污染物浓度变化与陆地径流关系密切,径流是感潮河段内突发事故中特征污染物输移的主导动力因素。 相似文献
11.
Mercury in the Tinto-Odiel Estuarine System (Gulf of Cádiz, Spain): Sources and Dispersion 总被引:1,自引:0,他引:1
The Tinto and Odiel are small rivers draining one of the largest sulphide deposits in the world. As a result of these deposits and a large industrial complex, the adjacent marine area receives a high amount of metal input. Mercury distribution in the Tinto-Odiel estuary, the Huelva Ría and the Gulf of Cádiz was assessed in water and suspended particulatematter (SPM) and sediments. In the rivers and estuaries, dissolved (HgD)and particulate (HgP) mercury showed wide variations (13 to 200 pM and0.3 to 330 nmol g-1 respectively) depending on the presence or notof sulphidic waters, phosphogypsum deposits, detrital pyrite and oxyhydroxides.In the Ría, concentrations were lower than 10 pM and 4.5 nmol g-1 for HgD and HgP respectively. In surface waters of the Gulf of Cádiz, the average HgD concentration (pm standard deviation) was 2.9 pm 0.9 pM, which is similar to that of North Atlantic Central Waters. The surface sediments collected in the rivers, the Ría and the Gulf showed systematically enriched mercury compared to pre-industrial levels. Vertical mercury profiles in dated sediment cores were typical of anthropogenically influenced environments starting in the early Roman age. These distribution features suggest that most of the Hg discharged by the Huelva Ría is trapped in the sediments of the Gulf of Cádiz. 相似文献
12.
Frank Jordan 《Estuaries and Coasts》2002,25(2):288-295
I examined the relative importance of beds of tapegrass (Vallisneria americana) and adjacent unvegetated habitats to juvenile and adult (6–35 mm standard length) rainwater killifish (Lucania parva) over a large spatial scale within the St. Johns River estuary, Florida. Abundance of rainwater killifish did not differ between oligohaline and tidal freshwater portions of the estuary and this species was relatively rare at opposite ends of the St. Johns River estuary. The presence of rainwater killifish at a given site was determined in part by large-scale variation in environmental factors such as habitat complexity and salinity. When present at a site, rainwater killifish were found almost exclusively in structurally complex beds of tapegrass. Behavioral observations in the laboratory indicated that rainwater killifish preferred vegetated over unvegetated habitats in the absence of both potential prey and predators and that use of vegetated habitats increased further upon addition of predatory largemouth bass (Micropterus salmoides). A laboratory predation experiment indicated that survival of rainwater killifish exposed to largemouth bass was significantly higher in vegetation than over open sand. Strong preferences for structurally complex vegetation likely reflect an evolved or learned behavioral response to risk of predation and help explain habitat use of rainwater killifish in the St. Johns River estuary. 相似文献
13.
An ephemeral estuarine turbidity maximum (ETM) occurs at high water in the macrotidal Taf estuary (SW Wales, United Kingdom).
A new mechanism of ETM formation, due to resuspension and advection of material by flood tidal currents, is observed that
differs from classical mechanisms of gravitational circulation and tidal pumping. The flood tide advances across intertidal
sand flats in the main body of the estuary, progressively entraining material from the rippled sands. Resuspension creates,
a turbid front that has suspended sediment concentrations (SSC) of about 4,000 mg I−1 by the time it reaches its landward limit which is also the landward limit of salt penetration. This turbid body constitutes
the ETM. Deposition occurs at high slack water but the ETM retains SSC values up to 800 mg I−1, 1–2 orders of magnitude greater than ambient SSC values in the river and estuarine waters on either side. The ETM retreats
down the estuary during the ebb; some material is deposited thinly across emergent intertidal flats and some is flushed out
of the estuary. A new ETM is generated by the next flood tide. Both location and SSC of the ETM scale on Q/R3 where Q is tidal range and R is river discharge. The greatest expression of the ETM occurs when a spring tide coincides with
low river discharge. It does not form during high river discharge conditions and is poorly developed on neap tides. Particles
in the ETM have effective densities (120–160 kg m−3) that are 3–4 times less than those in the main part of the estuary at high water. High chlorophyll concentrations in the
ETM suggest that flocs probably originate from biological production in the estuary, including production on the intertidal
sand flats. 相似文献
14.
The Mfolozi Estuary on the KwaZulu-Natal coast of South Africa is the most turbid estuary in Natal due to poor catchment
management, leading to large quantities of suspended particulate matter (SPM) entering the estuary from the Mfolozi River.
This paper quantities some of the solute and sediment dynamics in the Mfolozi Estuary where the main documented environmental
concern is the periodic input of SPM from the Mfolozi Estuary to the St. Lucia system, causing reduction of light penetration
and endangering biological productivity in this important nature reserve. Synoptic water level results have allowed reach
mean bed shear stresses and velocities to be calculated for an observed neap tidal cycle. Results indicate that ebb velocities
dominate the sediment transport processes in the estuary when fluvial input in the Mfolozi River is of the order of 15–20
m3 s–1. Observed and predicted flood tide velocities are too low (<0.35 m s–1) to suspend and transport significant amounts of SPM. Observed results indicate that although the SPM load entering the estuary
is dominantly from the Mfolozi River, the Msunduzi River flow plays a major role in the composition of the estuary's salinity
and velocity fields. It is calculated that the Mfolozi Estuary would fill with sediment in 1.3 years if it was cut off from
the sea. The major fluvial flood events help maintain the estuary by periodically pushing sediment seawards (spit progrades
seawards 5 m yr–1) and scouring and maintaining the main flow channel in the estuary. During low fluvial flow conditions, tidal flow velocities
will become the dominant control on sediment transport in the estuary. Interchange of SPM between the St. Lucia and Mfolozi
estuaries under present conditions is complicated by the strong transverse velocity shear between the two systems at their
combined mouth. This is creating a salinity-maintained axial convergence front that suppresses mixing of solutes and SPM between
the systems for up to 10 h of the tidal cycle during observed conditions.
Received: 22 May 1995 · Accepted: 31 July 1995 相似文献
15.
J. O. Blanton A. J. Garrett J. S. Bollinger D. W. Hayes L. D. Koffman J. Amft 《Estuaries and Coasts》2009,32(3):573-592
In late December 1991, an accidental release of 5,700 CI of tritiated water (HTO) from the Savannah River Site was transported
via site streams into the Savannah River where it was carried downstream to the coastal zone. HTO released into a semitropical
Georgia estuary was forced into the tidal marshes surrounding the estuary as well as discharged directly into the Atlantic
Ocean. The spreading of HTO was studied with a 3D hydrodynamic model (ALGE) that includes flooding and draining of intertidal
areas. Comparisons of model simulations to measured HTO concentration showed that ALGE simulated well the general increase
and decrease of HTO as its plume passed a given area. The “sheet flow” approximation for marsh and small tidal creek flow
largely compensated for lack of model resolution and accurate bathymetry in areas with numerous small to medium-sized tidal
creeks. The water volume of the unresolved tidal creeks had to be accounted for in the simulations by increasing the initial
water depth over the marshes. ALGE and a simple box model both reproduced the trapping of HTO in intertidal areas. The time
scale over which intertidal areas import and export HTO back to the tidal channels varies between 10 and 30 days. 相似文献
16.
Quarterly field sampling was conducted to characterize variations in water column and sediment nutrients in a eutrophic southern
California estuary with a history of frequent macroalgal blooms. Water column and sediment nutrient measures demonstrated
that Upper Newport Bay (UNB) is a highly enriched estuary. High nitrate (NO3
−) loads from the river entered the estuary at all sampling times with a rainy season (winter) maximum estimated at 2,419 mol
h−1. This resulted in water NO3
− concentration in the estuary near the river mouth at least one order of magnitude above all other sampling locations during
every seasons; maximum mean water NO3
− concentration was 800 μM during springer 1997. Phosphorus (P)-loading was high year round (5.7–90.4 mol h−1) with no seasonal pattern. Sediment nitrogen (N)-content showed a seasonal pattern with a spring maximum declining through
fall. sediment and water nutrients, as well as percent cover of three dominant macroalgae, varied between the main channel
and tidal creeks. During all seasons, water column NO3
− concentrations were higher in the main channel than in tidal creeks while tidal creeks had higher levels of sediment total
Kjeldhal nitrogen (TKN) and P. During each of the four sampling periods, percent cover ofEntermorpha intestinalis andCeramium spp. was higher in tidal creeks than in the main channel, while percent cover ofUlva expansa was always higher in the main channel. Decreases in sediment N in both creek and channel habitats were concurrent with increases
in macroalgal cover, possibly reflecting use of stored sediment TKN by macroalgae. Our data suggest a shift in primary nutrient
sources for macroalgae in UNB from riverine input during winter and spring to recycling from sediments duirng summer and fall. 相似文献
17.
Phillipe Monbet 《Estuaries and Coasts》2004,27(3):448-459
Cadmium (Cd) variations were investigated over an annual cycle (12 surveys between February 1998–January 1999) in the Morlaix
estuary (Brittany, France) in both the water column and the benthic compartment in relation to hydrological conditions. The
drainage basin of the Morlaix River estuary is predominantly agricultural in character. Dissolved Cd concentrations in the
water column varied from 0.04 to 0.48 nM. Particulate Cd concentrations ranged from 1 to 64 nmol g−1. These concentrations reach levels commonly observed in estuaries affected by heavy industrial activities. Extensive agricultural
activities in the drainage basin may be responsible for Cd levels above pristine conditions. Metal concentrations varied significantly
over the seasonal cycle and the dissolved fraction exhibited high values in summer months. Particulate concentrations were
always lowest during this season. In the benthic compartment, Cd concentrations in surface sediment varied from 0.4 to 5.0
nmol g−1 and from 0.2 to 5.0 nM in porewaters. Concentrations in sediment were slightly affected by Cd contamination and temporal
changes were important over the seasonal cycle. The variations seem to be controlled by the succession of sedimentation and
erosion processes, which are tightly linked to seasonal changes in river discharge. A box model was constructed based on known
Cd sources and sinks in the estuary. Cd is chiefly brought into the estuary by the Morlaix River and accumulates within the
estuary. The accumulation within the estuary represents from 6.3 to 7.2 kg yr−1. 相似文献
18.
Mudflats and associated mangroves are most important ecosystems of tropical coastal regions. Mangroves play a very important role in maintaining the environmental balance; thus in addition to mangrove reforestation and restoration, afforestation has also been practiced. We studied distribution of sediment components (sand, silt, clay) organic carbon (OC), heavy metals (Fe, Mn, Cu, Zn, Cr and Co) and pH in six cores collected from one of the largest mudflats of Mandovi estuary, west coast of India. The temporal distribution patterns of these proxies suggested that past changes in tidal energy conditions, fresh water inflow and anthropogenic activities over the last few decades, together helped in development of a middle tidal flat in this estuary. In cores collected from the mangroves, trapping and deposition of finer particles and organic matter were enhanced by a complex aerial mangrove root system in recent years. Mangroves were, therefore, suggested to enhance the buildup of mudflats in Mandovi estuary. Cores collected from mudflats also exhibited higher deposition of finer particles and organic matter (except MF2) in recent years, suggesting maturity and greater stability of the entire mudflat in recent years. Middle tidal flats (mudflats) of Mandovi estuary may, therefore, prove to be suitable substrates for mangrove proliferation in the near future. Finer sediments deposited mainly from mining activities in recent years exhibited lower pH and higher metal content. Organisms dwelling in these recently deposited sediments are, therefore, at higher risk of bioaccumulation and metal toxicity. 相似文献
19.
Groundwater pollution by Cystine manufacturing industrial effluent around the factory 总被引:1,自引:0,他引:1
The pollution potential of Cystine industrial effluents on groundwater pollution is assessed. The results indicate that the
Cystine industrial effluent which is partially treated and stored in lagoons contains a high concentration of inorganic solids
and soluble organics. The percolation of these effluents caused groundwater pollution impairing the water quality.
Received: 20 April 1999 · Accepted: 7 June 1999 相似文献
20.
Heavy metals on tidal flats in the Yangtze Estuary, China 总被引:7,自引:0,他引:7
Five short cores were used to examine heavy metals on tidal flats in the Yangtze Estuary, China. Statistically insignificant
trends in lead-210 and most metals with core depth are primarily due to high sedimentation rates. Metal contents are correlated
with percent aluminum, which reflects the clay contents in the sediment, and they are also affected by proximity to sewage
outlets and local industry. National standards for copper are exceeded in four cores, zinc in one core, and arsenic in all
cores. Heavy metal contents are generally lower on the Yangtze tidal flats compared to most other estuaries because high sediment
loads dilute metal inputs.
Received: 1 June 1999 · Accepted: 15 August 2000 相似文献