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1.
为研究淤泥质河口的水沙运动规律,建立了用于模拟淤泥质河口水沙运动的二维数学模型。该模型采用基于无结构三角网格下的有限体积法对方程组进行离散,结合Roe-MUSCL方法及时间方向的预测-校正格式,使模型在时空方向具有二阶计算精度。模型中分别采用不同方法计算粘性和非粘性泥沙的输移源项,并引入粘性泥沙的起动流速和冲刷率计算公式。采用已有的概化水槽试验数据对模型进行了初步验证。然后模拟了1995年10月小潮及大潮期间海河口的潮流运动与泥沙输移过程,计算得到的潮位、潮流速及含沙量过程与实测过程符合较好,结果表明模型能够用来模拟淤泥质河口粘性和非粘性泥沙的不平衡输移过程。同时还比较了泥沙输移源项的不同处理方式对计算结果的影响,计算表明在淤泥质河口水沙运动数学模型中必须同时考虑粘性和非粘性泥沙的输移。 相似文献
2.
为更加准确地模拟重金属随泥沙迁移的过程,避免传统模型在描述重金属的吸附解吸时只能片面地考虑简单物理过程的不足,在水沙输移模拟的基础上,同时考虑了重金属随泥沙迁移的物理和化学过程,建立了完整的水动力-泥沙-重金属迁移数学模型。模型利用泥沙颗粒表面复杂形貌与电荷的关系来修正表面络合模型并以此分析了水体中的重金属与泥沙颗粒表面基团间的化学成键作用,同时根据化学反应的不同条件,并结合床面冲淤,将床面泥沙分为有氧层和无氧层分别考虑重金属的沉积与再释放。模型模拟了水槽试验中重金属Ni随泥沙迁移的情况,计算结果与实测数据的对比表明了建立的模型可以合理地反映重金属随泥沙的迁移过程。 相似文献
3.
为更加准确地模拟重金属随泥沙迁移的过程,避免传统模型在描述重金属的吸附解吸时只能片面地考虑简单物理过程的不足,在水沙输移模拟的基础上,同时考虑了重金属随泥沙迁移的物理和化学过程,建立了完整的水动力-泥沙-重金属迁移数学模型。模型利用泥沙颗粒表面复杂形貌与电荷的关系来修正表面络合模型并以此分析了水体中的重金属与泥沙颗粒表面基团间的化学成键作用,同时根据化学反应的不同条件,并结合床面冲淤,将床面泥沙分为有氧层和无氧层分别考虑重金属的沉积与再释放。模型模拟了水槽试验中重金属Ni随泥沙迁移的情况,计算结果与实测数据的对比表明了建立的模型可以合理地反映重金属随泥沙的迁移过程。 相似文献
4.
大量重金属污染物迁移转化的现象和研究成果都表明重金属以泥沙颗粒为载体迁移转化,描述重金属在天然水体中的迁移转化必须紧紧抓住泥沙颗粒运动及重金属与泥沙之间的转化关系进行.为此在对现有的重金属迁移转化数学模型进行概括分类的基础上,根据水沙运动与污染物相互作用关系,分析了泥沙颗粒运动及重金属吸附解吸不平衡过程,并结合水沙数学模型,建立了重金属迁移转化的耦合模型.同时在模型合理性分析的基础上,对模型进行了计算分析,分析表明模型能够合理地反映重金属污染物在水体中的迁移转化过程. 相似文献
5.
生源物质作为影响水质的重要因素,其在河流中的迁移转换一直倍受关注。水沙界面物质交换过程受众多环境和水动力因素的影响,过程极其复杂,不仅影响着河流生源要素的通量演变规律,还关系到河流水环境问题。为探究水沙界面生源物质迁移转化过程及作用机制,结合国内外研究最新进展,对泥沙颗粒与生源物质的微界面作用、水沙界面对生源物质的迁移转化作用、水流条件对泥沙吸附解吸生源物质作用机理进行总结和概述,总结阐述了河流水质模型和闸坝泵条件下的水环境调控模型,最后指出平原河流水沙运动对生源物质输运作用机理及水环境调控。针对上述已有的研究成果和存在不足,对今后研究方向提出展望。 相似文献
6.
构建起双向耦合的液固两相流动旋涡动力学模型与数值方法;应用离散涡方法,计算非定常不稳定水流场;采用Lagrange方法模拟颗粒运动,颗粒对流体的反作用通过修正涡泡运动速度来实现。利用所建模型,计算了两种St数的泥沙粒子在圆柱绕流场中的运动。结果证明了液固两相流动中颗粒运动与旋涡存在着明确的相关结构:(1)当水沙混合物中的泥沙颗粒碰上旋涡时,泥沙颗粒被卷入旋涡中,被卷入旋涡中的泥沙颗粒在运动过程中始终分布于旋涡区;(2)均匀水沙混合物绕圆柱流动,由于流体流过圆柱时产生剧烈分离流动,使得在尾迹流内中等St数 (St～o (1))的泥沙颗粒从均匀水沙混合物中分离出来而往旋涡区聚集。 相似文献
7.
8.
目前"井孔-含水层"系统处理的三种主要方法:基于线汇理论的井孔模拟、高渗透系数法和渗流-管流耦合模型,评述了各种方法的优缺点,重点指出了传统线源(汇)法理论上的缺陷及实际应用中的局限性。概括了MODFLOW,TOUGH2,FEFLOW等地下水数值模拟软件对井孔含水层模拟的方法;应加强井周小尺度水流水质的精细研究,并研究井周水流运动对水质的作用,以及对大尺度地下水模拟的影响。 相似文献
9.
秦皇岛市洋河、戴河滨海平原海水入侵的控制与治理 总被引：5，自引：0，他引：5
秦皇岛市洋河,戴河冲洪积平原,近20年来抽取地下水量迅速增加,80年代初形成了低于海平面的降落漏斗,造成海水从海岸线向内陆和从河流下游河床向两侧同时侵入孔隙含水层。由于水质恶化,北戴河区水源地面临报废的危险。为了保护和开发淡水资源,控制海水入侵,必须对地下水的水质和水量进行综合评价。采用水动力弥散型地下水水质模型来描述滨海含水层中海水和淡水的运动,把氯离子作为水质模型的变量。在水量模型中采用孔隙压力代替水头作为变量。数学模型用有限单元法求解。模拟面积约180km2,剖分为321个单元,184个结点。作为水文地质实体的模型,它被用来模拟和预报不同降水量年份的地下水水位和水质。计算结果表明,如果保持目前的地下水开采量,海水入侵还会深入。为了控制和治理海水入侵,本文探讨了可行措施。根据数学模型模拟的结果,在洋河下游人海口修建防潮闸,同时加强滨海含水层的管理,具有较好的经济效益和环境效益。 相似文献
10.
河流泥沙模拟技术进展与展望 总被引：4，自引：1，他引：4
本文系统总结了河流模拟技术的发展过程和研究成果。河流模拟技术包括河流实体模型和泥沙数学模型两部分。在实体模型方面,已建立了一整套河工模型的相似理论、设计方法和试验技术,在模型变态、模型沙选择、高含沙水流模拟、模型测验等方面取得了重要的研究成果,并解决了大量的工程泥沙问题。在数学模型方面,建立了一维、二维和三维泥沙数学模型,并随着泥沙基本理论研究的不断深入与广泛的工程应用,在计算模式、数值计算方法、计算结果的后处理、参数选择、高含沙水流问题处理等方面均取得了重要进展。本文还展望了河流模拟技术今后的发展方向。 相似文献
11.
Estuaries receive large quantities of suspended sediments following the first major storm of the water year. The first-flush events transport the majority of suspended sediments in any given year, and because of their relative freshness in the hydrologic system, these sediments may carry a significant amount of the sediment-associated pesticide load transported into estuaries. To characterize sediment-associated pesticides during a first-flush event, water and suspended sediment samples were collected at the head of the San Francisco Bay during the peak in suspended sediment concentration that followed the first major storm of the 1996 hydrologic year. Samples were analyzed for a variety of parameters as well as 19 pesticides and degradation products that span a wide range of hydrophobicity. Tidal mixing at the head of the estuary mixed relatively fresh suspended sediment transported down the rivers with suspended sediments in estuary waters. Segregation of the samples into groups with similar degrees of mixing between river and estuary water revealed that transport of suspended sediments from the Sacramento-San Joaquin drainage basin strongly influenced the concentration and distribution of sediment-associated pesticides entering the San Francisco Bay. The less-mixed suspended sediment contained a different distribution of pesticides than the sediments exposed to greater mixing. Temporal trends were evident in pesticide content after samples were segregated according to mixing history. These results indicate sampling strategies that collect at a low frequency or do not compare samples with similar mixing histories will not elucidate basin processes. Despite the considerable influence of mixing, a large number of pesticides were found associated with the suspended sediments. Few pesticides were found in the concurrent water samples and in concentrations much lower than predicted from equilibrium partitioning between the aqueous and sedimentary phases. The observed sediment-associated pesticide concentrations may reflect disequilibria between sedimentary and aqueous phases resulting from long equilibration times at locations where pesticides were applied, and relatively short transit times over which re-equilibration may occur. 相似文献
12.
M. Saeedi Sh. Daneshvar A. R. Karbassi 《International Journal of Environmental Science and Technology》2004,1(2):135-140
Riverine sediments and suspended matters have been subjected to several bench scale tests for the evaluation of adsorption potential of heavy metals. For this purpose water, sediment and suspended particulate matters of Tadjan River (southern part of the Caspian Sea) were collected. In the vicinity of the river many polluting sources were recognized; for instance, pulp and paper mill, dairy factory and municipal sewage that can introduce various amounts of heavy metals into the river water. Bottom sediments and suspended particulate matters have been individually subjected to adsorption tests. The results of analysis showed that riverine bottom sediments have greater potential for adsorbing heavy metals than suspended matters. However the trend of adsorption in both sediments and suspended matters are similar. Maximum adsorption capacity of heavy metals (in terms of mg of metal per kg of sediments and suspended matters) by sediments and suspended matters are as: Sediments: Cu (2200)> Mn (2000)> Ni (1400)> Zn (320) Suspended matters: Cu (2100)> Ni (1500)> Mn (1200)> Zn (310) Further, results revealed that increasing concentration of metals would cause desorbing Cadmium from both sediments and suspended matters. 相似文献
13.
Suspended-sediment and water samples were collected from San Francisco Bay in 1991 during low river discharge and after spring rains. All samples were analyzed for organophosphate, carbamate, and organochlorine pesticides; petroleum hydrocarbons; biomarkers; and polynuclear aromatic hydrocarbons. The objectives were to determine the concentrations of these contaminants in water and suspended sediment during two different hydrologic conditions and to determine partition coefficients of the contaminants between water and sediment. Concentrations of hydrophobic contaminants, such as polynuclear aromatic hydrocarbons, varied with location of sample collection, riverine discharge, and tidal cycle. Concentrations of hydrophobic contaminants in suspended sediments were highest during low river discharge but became diluted as agricultural soils entered the bay after spring rains. Polynuclear aromatic hydrocarbons defined as dissolved in the water column were not detected. The concentrations sorbed on suspended sediments were variable and were dependent on sediment transport patterns in the bay. In contrast, the relatively hydrophilic organophosphate pesticides, such as chlorpyrifos and diazinon, has a more uniform concentration in suspended sediment. These pesticides were detected only after spring rains. Most of the measured diazinon, at least 98% for all samples, was in the dissolved phase. Measured partition coefficients for diazinon generally were uniform, which suggests that suspended-sediment concentrations were close to equilibrium with dissolved concentrations. The concentration of diazinon sorbed to suspended sediments, at any given sampling site, was driven primarily by the more abundant solution concentration. The concentrations of diazinon sorbed to suspended sediments, therefore, were independent of the patterns of sediment movement. 相似文献
14.
Sediments from the Mackenzie Valley — two suspended and one river bottom — were analyzed for major and minor elements, mineralogy,
particle size, and ability to release trace metals when subjected to mild leaching.
Copper and zinc in suspended sediments and cadmium in bottom sediment occurred largely (70 to 84 percent for Cu, 72 to 98
percent for Zn, 75 to 81 percent for Cd) in a form that could not easily be separated from the sediments by 0.1M HC1 and EDTA
solutions. Cadmium was present in suspended sediments in low concentrations, and was present totally in sorbed leachable form.
Iron, manganese, cobalt and chromium were separable from the particulate phase by mild leaching. It was found that approximately
70 hours were required for an apparent steady state concentration to be attained in such leachings.
Reaction of these sediments with Beaufort Sea water (salinity 22.3 parts per thousand) indicated that both iron and manganese
were released from sediments to sea water to a very small degree. Copper, lead, and zinc, however, were absorbed by sediments
from sea water. 相似文献
15.
Lake Houston is a man-made reservoir located northeast of Houston, Texas. The purpose of this investigation was to document
suspended sediment transport, sedimentation, and resuspension in the lake with a view towards estimating the influence of
sedimentation on water quality. Sediment traps were placed in strategic locations in the lake to collect suspended sediments.
Samples were analyzed for bulk density, grain size, organic carbon, and a number of trace elements. These data were analyzed
along with meteorological data to examine those factors which regulate suspended sediment input and dispersal, and the role
of suspended sediments in controlling water quality within the lake.
Sediment input to the lake depends primarily on the intensity of rainfall in the watershed. Sediment movement within the lake
is strongly influenced by wave activity, which resuspends sediments from shallow areas, and by wind-driven circulation. The
increased residence time of suspended sediments due to resuspension allows greater decomposition of organic matter and the
release of several trace elements from sediments to the water column.
Virtually all samples from sediment traps suspended between 1 and 5 m above the lake bottom contain medium to coarse silt,
and even some very fine sand-sized material. This implies that circulation in Lake Houston is periodically intense enough
to transport this size material in suspension. During winter, northerly winds with sustained velocities of greater than 5
m/sec provide the most suitable condition for rapid (<1 d) transport of suspended sediment down the length of the lake.
Fluctuations in current velocities and the subsequent suspension/deposition of particles may explain variations in the abundance
of coliform bacteria in Lake Houston. 相似文献
16.
A. L. Ramanathan P. Vaithiyanathan V. Subramanian B. K. Das 《Estuaries and Coasts》1993,16(3):459-474
Major ion chemistry of water and elemental geochemistry of suspended and surficial sediments collected from the Cauvery Estuary were studied to understand the geochemical processes in this tropical estuarine system. Specific conductance (EC), total dissolved solids (TDS), and total suspended matter (TSM) increased conservatively with increasing chlorinity. In general, SO4 2?, Na, K, Ca, and Mg showed an increasing trend while H4SiO4 and PO4 3? showed a decreasing trend toward the sea. Additional removal mechanisms operating for these ions in the Cauvery Estuary have been identified based on observed concentrations. Factor analysis pointed out the sources contributing to the observed trends in estuarine water chemistry. POC and PON decreased toward the high chlorinity zone. TSM in the Cauvery Estuary were mostly of inorganic nature. Stable carbon isotope values showed that the carbon was equally of marine and terrestrial origin and helped to delineate the contribution of river water and seawater. The ? mean size (a logarithmic grain size scale commonly used by sedimentologists) indicated that the surficial sediments were primarily comprised of coarse and silt, whereas suspended sediments were principally silt and clay. Suspended sediments were enriched in clays compared to surficial sediments. Quartz and feldspar were abundant among detritals while chlorite, kaolinite, and montmorillonite were dominant among clays. Silicon was the most abundant element in the sediments followed by Al, Ca, Na, K, Fe, Mn, and P. Heavy metals were enriched in the suspended sediments compared to the surficial bottom sediments as follows: Fe = 3.5, Mn = 7.4, Pb = 1.1, Zn = 15.2, Cu = 7.4, and Cr = 4.0. The levels of Cd, Cr, Zn, and Fe increased up the middle reaches and then decreased toward the sea due to urban effluent and fertilizer input. Size fractionation studies indicated that the metal concentration in the finer fraction was 50% higher by mass than the coarse silt and fine silt fractions. Chemical fractionation studies showed that the abundance of metals were in the order of residual > organic/sulfide > carbonate > Fe/Mn oxide > exchangeable fractions. 相似文献
17.
《Applied Geochemistry》2001,16(1):95-108
Bottom sediments and suspended matter from the shelf and slope areas off northeastern Taiwan were analyzed for sterol, n-alkanol and n-alkane compositions. The Σ(algal sterols/cholesterol) ratios (mean±1σ) were 1.00±0.31 (n=7) for the shelf sediments, 3.29±0.61 (n=7) for the slope sediments, and 1.54±0.19 (n=3) for the suspended matter. The much higher proportion of cholesterol in the shelf sediments is most likely derived from mollusks in the relict sediments. An additional sterol source for the shelf sediments probably is suspended matter in the water column although the shelf has no apparent sedimentation. Results from phytol and n-alkanols suggest recent inputs of lipids from the water column to the shelf. The stanol/stenol ratios are lower for the older shelf sediments than for the younger slope sediments. 相似文献
18.
V. N. Lukashin 《Geochemistry International》2008,46(7):711-723
This paper reports the results of a geochemical study of suspended particulate matter and particle fluxes in the Norwegian Sea above the Bear Island slope. The concentrations of suspended particles and the main components of suspended matter were determined in the euphotic, intermediate (“clean water”), and bottom nepheloid layers. It was shown that biogenic components are predominant in the water above the nepheloid layer, whereas the suspended matter of the nepheloid layer is formed by the resuspension of the lithogenic components of bottom sediments. The chemical compositions of suspended matter and material collected in sediment traps are identical. 相似文献
19.
Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry
and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO3 is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering
aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO4 and PO4 at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica,
relatively high (Na+K)/TZ+ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering
of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season,
reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive
correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite
is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water
favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher
than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting
that there is no pollution from these metals in Damodar River sediments.
Received: 21 January 1998 · Accepted: 4 May 1998 相似文献