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1.
A 2D depth-averaged numerical model is set up to simulate the macro-scale hydrodynamic characteristics, sediment transport patterns and morphological evolution in Hangzhou Bay, a large macro-tidal estuary on the eastern coast of China. By incorporating the shallow water equations, the suspended sediment transport equation and the mass-balance equation for sediment; short-term hydrodynamics, sediment transport and long-term morphological evolution for Hangzhou Bay are simulated and the underlying physical mechanisms are analyzed. The model reproduces the spatial distribution patterns of suspended sediment concentration (SSC) in Hangzhou Bay, characterized by three high SSC zones and two low SSC zones. It also correctly simulates the residual flow, the residual sediment transport and the sediment accumulation patterns in Hangzhou Bay. The model results are in agreement with previous studies based on field measurements. The residual flow and the residual sediment transport are landwards directed in the northern part of the bay and seawards directed in the southern part. Sediment accumulation takes place in most areas of the bay. Harmonic analysis revealed that the tide is flood-dominant in the northern part of the bay and ebb-dominant in the southern part of the bay. The strength of the flood-dominance increases landwards along the northern Hangzhou Bay. In turn sediment transport in Hangzhou Bay is controlled by this tidal asymmetry pattern. In addition, the direction of tidal propagation in the East China Sea, the presence of the archipelago in the southeast and the funnel-shaped geometry of the bay, play important roles for the patterns of sediment transport and sediment accumulation respectively.  相似文献   

2.
The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore, there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay. With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eu-trophication.  相似文献   

3.
Water from the Susquehanna River was collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl (PCB) congeners to estimate seasonal and annual riverine loads to the Chesapeake Bay. Temporal variations in the chemical loads resulted from the large changes in the water flow rates and in the particle-associated contaminant concentrations. Concentrations of PCBs and PAHs in river particles (ng/g) were twice as great as those in the northern Chesapeake Bay, indicating that the Susquehanna River is an important source of these contaminants to the bay. The river carries a majority of its hydrophobic organic contaminants (HOCs) in the particulate phase. During periods of high flow, large amounts of suspended particles in the river result in elevated HOC levels and increased loadings of these contaminants to the bay. From 1997 to 1998, 60% of the total annual HOC loading occurred in the early spring coincident with high river flows. The total PCB and PAH annual loadings from the Susquehanna River to the Chesapeake Bay were 76 and 3160 kg/year, respectively and 75% of the loaded organic contaminants were in the particulate phase. Principal component analysis of PAH and PCB congener patterns in the particles reveals that the river suspended particles were dominated by autochthonous production in the summer and by resuspended sediment and watershed erosion during the winter and early spring.  相似文献   

4.
The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore, there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay. With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.  相似文献   

5.
徐起浩 《华南地震》2006,26(1):17-27
根据琼州府志、琼山县志及一些家谱、族谱等的记载,再加上对海域中退潮后海底残留的房屋、坟墓等各种沉没于海的人类活动废墟和东寨港海域中地震地貌的发现与考察,结合本人和前人以往的研究成果,证实1605年7月13日海南岛琼山县发生的71/2级强地震导致琼州海峡东南侧与琼北陆地相连的海底及与海相连的琼北东部一些沿岸陆地大面积同震快速下沉,使得原先为陆地的东寨港、北创港和舖前港及其以北海域等地区大面积陆陷成海。这是一次生源地在与海相连的海岸带的同震海岸下沉。推断了这次地震海啸;比较了这次陆陷成海地震海啸与生源地在近海和大洋海底的地震海啸的异同;也与北美西海岸生源地在太平洋板块斜插在北美大陆板块之下形成消减带的海岸同震下沉及海啸比较了异同。最后还提出,琼州大地震陆陷成海灾害应从根本上区别通常所说的震陷灾害。  相似文献   

6.
Surface water samples from marinas, commercial ports and open bay areas collected from Biscayne Bay and the Miami River, Florida, USA, were analyzed for the occurrence of IRGAROL 1051 by GC/MS. The anifouling boosting herbicide was found in 80% (46/57) of the samples collected between March 1999 and September 2000. Concentrations within the bay range between non-detected (<1 ppt) and 61 ppt (ng/L) and were generally low compared with levels reported in European or Japanese waters. Aside from the elevated concentrations observed along the Miami River South Fork (61 ppt), the highest concentrations observed in the bay corresponded to marinas with high density of pleasure craft and restricted water circulation. In contrast, occurrence of IRGAROL 1051 along the commercial port or the cruise line terminal was generally lower (<1-2.2 ppt). Concentrations around Coconut Grove Marina were consistently higher (5-12 ppt) than the rest of the bay waters during the whole period of time surveyed.  相似文献   

7.
中国大陆及邻近地区上地幔顶部Sn波速度层析成像   总被引：10，自引：1，他引：9       下载免费PDF全文
利用《中国地震年报》中43646条Sn射线的走时资料,采用层析成像方法反演了中国大陆地区上地幔顶部的Sn波速度结构. 主要结果是：①全国平均Sn速度为4.55km/s,速度变化量从-0.14km/s到+0.15km/s. ②整体上中国Sn速度分布是东低西高,塔里木盆地、准噶尔盆地、吐鲁番—哈密盆地以及柴达木盆地东端、四川盆地及其南部地区等是明显的高Sn速度区,鄂尔多斯地台和台湾海峡也是Sn速度较高地区,整个华北盆地、渤海湾东部、山西北部和郯庐断裂带,Sn速度都比较低. 另外,长江中下游地区、青藏高原北部和南北地震带地区,Sn速度也较低. ③ Sn速度变化分布和构造活动、地壳厚度以及大地热流变化有关,分别求得了速度与地壳厚度和大地热流的线性回归方程. ④ Sn速度变化和Pn速度变化的区域分布总体上是吻合的.  相似文献   

8.
Polycyclic aromatic hydrocarbons (PAHs) were measured in 41 surface sediments from Narragansett Bay, RI. All the analytes generally decrease down bay from the Seekonk, Providence and Taunton Rivers at the head of the bay. Total PAHs ranged from 0.569 to 216 microg/g with 27% exceeding the effects range median (ERM) of 44.8 microg/g and 73% of the stations exceeding the effects range low (ERL) of 4.02 microg/g (Long et al., 1995). Based on principal component analysis, the major source of the contaminants in Narragansett Bay was the Providence River while the coves and Taunton River/Mt. Hope Bay appeared to only have a limited influence on the open bay. PAH source ratios indicate that creosote and/or coal may be the most significant contributor of pyrogenic high molecular weight PAHs in Narragansett Bay, along with significant contributions from diesel exhaust.  相似文献   

9.
《Continental Shelf Research》1987,7(10):1139-1159
Princess Charlotte Bay, located on the northern Great Barrier Reef, is an environment of terrigenous and carbonate deposition. The dynamics on this shelf are controlled by the Great Barrier Reef at the edge of the shelf, and the mid-shelf, shore-normal reefs. This study examines the dynamics during the dry season, with six time-series records from instrumented tripod deployments and numerous hydrographic stations.The shallow nearshore waters and the estuaries prove to be the sites where most active sediment resuspension and transport takes place. Sediment resuspension is effected primarily by waves in the nearshore, and channeling of tidal currents in the estuaries. Bedload transport did not occur during this study, mainly because current velocities were too low. Suspended particulate matter (SPM) transport in the bay is governed by tides and winds. Strong tidal flow imparts a strong offshore component to the transport, and strong southeast winds impart an alongshore component that transports SPM out of the bay to the northwest. Rattlesnake Channel, east of Princess Charlotte Bay, is another route by which SPM leaves the bay. Flow through this channel is predominantly tidal, with ebb waters (leaving Princess Charlotte Bay) carrying higher SPM concentrations than flood waters.SPM flux in the nearshore was an order of magnitude higher than at offshore stations, with highest fluxes generally occurring at times of sustained southeast winds. Transect data show that SPM drops to average bay values in water 11 m deep, indicating most SPM is transported in nearshore waters.  相似文献   

10.
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11.
Horizontal and vertical distributions of organochlorine compounds (OCs) were determined in sediments from Masan Bay. The concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), HCB, hexachlorocyclohexanes (HCHs) and chlordane related compounds (CHLs) in sediments were in the range of 1.24-41.4, 0.28-89.2, 0.02-0.59, nd-1.03, and nd-2.56 ng/g, respectively. The spatial distribution of OCs showed a negative gradient from the inner of the bay to outer part of the bay, indicating that the source of OCs was probably located inside the bay. Compositional pattern of PCB congeners showed a relatively high concentration of high-chlorinated congeners in the inner part of the bay and a relatively low concentration of low-chlorinated congeners in the outer part. In sediment core from Masan Bay maximum concentrations of PCBs and DDTs are observed in the subsurface samples and correspond to an age of early 1980s and late 1960s. The concentration profiles of PCBs and DDTs in sediments of Masan Bay appear to correspond to use of PCBs and DDTs in Korea.  相似文献   

12.
Previous studies of weathering generally started with geochemistry[1—8] and mineralogy[9—12], and have been focused on chemical weathering rates[1—3], removability-enrichment of elements[3—6] during chemical weathering, and the age of weathering profi…  相似文献   

13.
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   

14.
The response of the density-driven circulation in the Chesapeake Bay to wind forcing was studied with numerical experiments. A model of the bay with realistic bathymetry was first applied to produce the density-driven flow under average river discharge and tidal forcing. Subsequently, four spatially uniform wind fields (northeasterly, northwesterly, southwesterly, and southeasterly) were imposed to examine the resulting cross-estuary structure of salinity and flow fields. In general, northeasterly and northwesterly winds intensified the density-driven circulation in the upper and middle reaches of the bay, whereas southeasterly and southwesterly winds weakened it. The response was different in the lower bay, where downwind flow from the upper and middle reaches of the bay competed with onshore/offshore coastal flows. Wind remote effects were dominant, over local effects, on volume transports through the bay entrance. However, local effects were more influential in establishing the sea-level slopes that drove subtidal flows and salinity fields in most of the bay. The effect of vertical stratification on wind-induced flows was also investigated by switching it off. The absence of stratification allowed development of Ekman layers that reached depths of the same order as the water depth. Consequently, bathymetric effects became influential on the homogeneous flow structure causing the wind-induced flow inside the bay to show a marked transverse structure: downwind over the shallow areas and upwind in the channels. In the presence of stratification, Ekman layers became shallower and the wind-induced currents showed weaker transverse structure than those that developed in the absence of stratification. In essence, the wind-driven flows were horizontally sheared under weak stratification and vertically sheared under stratified conditions.  相似文献   

15.
Murchison Bay is a shallow embayment in the north-western part of Lake Victoria, strongly influenced by urban pollution from the Ugandan capital Kampala. Two stations, representing the semi-enclosed innermost part of the bay and the wider outer part of the bay, were sampled in the period from April 2003 to March 2004, in order to assess the phytoplankton community and the nutrient status in the bay. Murchison Bay was highly eutrophic with average concentrations (n=25) of total phosphorous >90 μg L−1 and total nitrogen >1100 μg L−1 in the inner part of the bay. The phytoplankton community was dominated by a variety of cyanobacterial species and diatoms. Cyanobacteria were dominant in the whole bay, whereas diatoms were more abundant in the outer part of the bay. Moreover, the proportion of N-fixing species like Anabaena sp. was higher in the outer part of the bay, whereas species like Microcystis sp. were more abundant in the inner part of the bay. The phytoplankton community, especially in the outer part of the bay, may be influenced by light limitation. Low NO3-N concentrations in the bay may also indicate a possible N-limitation, thus favouring growth of N-fixing cyanobacteria. The open bay is, however, a complex system, and additional environmental factors and loss processes most likely affect the phytoplankton community.  相似文献   

16.
This study evaluates the magnitude and extension of the impact produced by the discharge of inert allochthonous materials, including clays and particulate iron, on macrobenthic soft-bottom assemblages in the subtidal zone of a coastal bay in north-central Chile. An average of 118 Ton h(-1) of finely divided solids were discharged into the rocky intertidal zone of the bay for a period of over 16 years, producing continuous turbidity in the water column and sedimentation in the subtidal zone. Data obtained four months before cessation of the discharge showed that the macrofauna present at 20 and 50 m depth in the bay suffered an important decrease in abundance and species richness, low diversity/high dominance, and deep changes in community structure related to the discharge. The faunal assemblages present at 110 m depth did not show effects from the discharge, suggesting that the impact was limited to the inner part of the bay. The impoverished faunal aggregates at 20 and 50 m depth showed exclusive domination by the Lumbrineris bifilaris (polychaete)-Diastylis tongoyensis (cumacean) association, representing a simple trophic guild of deposit feeders. The complete absence of opportunistic species such as capitellid, spionid, and/or cirratulid polychaetes may be associated with the turbidity and sedimentation levels in the bay.  相似文献   

17.
The distribution of polycyclic aromatic hydrocarbons (PAHs) has been investigated in the surface and core sediments from Masan Bay, Korea. Total PAHs in the surface sediments ranged from 207 to 2670 ng/g dry weight with a mean value of 680 ng/g. Qualitative similarity and quantitative difference between inner and outer bay indicate that the main sources of PAHs are located in the inner bay and outer bay is also affected by the same sources. Vertical distribution of PAHs revealed that three distinctive stages could be differentiated with the help of PCA analysis. The highest concentration (industrialization stage) appeared between late 1950s and 1980, which was 10 years later than other developed countries. A strong pyrolytic source fingerprint has been detected with slight influence of petrogenic sources, and diagenetic PAH, perylene also contributed. Total organic carbon normalized PAHs (sum of 13 PAHs, 8.85-88.0 microg/g OC) were under the threshold effects concentration (TEC, 290 microg/g OC).  相似文献   

18.
A 2D Hydrodynamic-Particle Analysis model was applied to the Gulf of Kachchh (GoK) to estimate the residence time of pollutants. The tidal currents in the Gulf have a strong E-W component, which prevents the material in the north being transported towards south. In the regions situated very close to the open boundary, where the GoK waters exchange freely with the northern Arabian Sea, dilution takes place rapidly with the incoming waters and hence, the residence time is on the order of 1 day. Influence of eddies and a dynamic barrier across the Sikka-Mundra section on the residence time is apparent. Eastern GoK shows a relatively large residence time, on the order of 2-4 days, warranting caution while releasing industrial wastes in the northeastern Gulf. The region around location-5 behaves like a bay; the dissolved matter gets trapped in this bay and the residence time increases by 3-4 days.  相似文献   

19.
Three sediment cores were collected from the top to the mouth of Quanzhou Bay, Southeast China, in order to establish sources and historical trends of organochlorine pesticides (OCPs) in the region. The spatial distribution of OCPs in surface sediments implies that Quanzhou Bay received the contamination inputs not only from rivers near the shore, but also from outside the bay. The variation profiles of concentrations clearly showed that OCPs were widely used between 1960s and 1980s in China. A recent increasing trend was found in all cores despite their ban in China in 1983. Different ratios of (DDD+DDE)/DDTs indicated that DDTs at the top of the bay were mainly derived from long-term weather soils, while DDTs near the mouth of the bay were mainly derived from fresh inputs from outside the bay. Higher percentage of gamma-HCH in HCHs deposited after 1990 implies that lindane may have been used recently around Quanzhou Bay.  相似文献   

20.
The concentrations of airborne fission products were observed to be air mass dependent during a cruise of the USNSHayes from Norfolk, Va to Athens, Greece in May–June 1977. Minimum concentrations of fission products, radon, and CCN (cloud condensation nuclei) were measured in maritime air which had previously transited northern North America. Higher fission products, radon, and CCN concentrations were measured in recent, continental air traceable to mid North America or central Europe. These data are consistent with either entrainment by strong winds of previously precipitated fission products (the continental effect) or greater transfer of fission products from the stratosphere to low levels by tropospheric folding.  相似文献   

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