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1.
Patrick Ollivier Christelle Claude Olivier Radakovitch Bruno Hamelin 《Marine Chemistry》2008,109(3-4):337
Submarine groundwater discharge (SGD) is now recognized as an important pathway for water and chemical species fluxes to the coastal ocean. In order to determinate SGD to the Gulf of Lion (France), we measured the activities of 226Ra and 228Ra by thermal ionization mass spectrometry (TIMS) in coastal waters and in the deep aquifer waters of the Rhone deltaic plain after pre-concentration of radium by MnO2. Compared to conventional counting techniques, TIMS requires lower quantities of water for the analyses, and leads to higher analytical precision. Radium isotopes were thus measured on 0.25–2 L water samples containing as little as 20 fg of 226Ra and 0.2–0.4 fg of 228Ra with precision equal to 2%. We demonstrate that coastal surface waters samples are enriched in 226Ra and 228Ra compared to the samples further offshore. The high precision radium measurements display a small but significant 226Ra and 228Ra enrichment within a strip of circa 30 km from the coast. Radium activities decrease beyond this region, entrained in the northern current along the shelf break or controlled by eddy diffusion. The radium excess in the first 30 km cannot be accounted for by the river nor by the early diagenesis. The primary source of the radium enrichment must therefore be ascribed to the discharge of submarine groundwater. Using a mass-balance model, we estimated the advective fluxes of 226Ra and 228Ra through SGD to be 5.2 × 1010 and 21 × 1010 dpm/d respectively. The 226Ra activities measured in the groundwater from the Rhone deltaic plain aquifer are comparable to those from other coastal groundwater studies throughout the world. By contrast, 228Ra activities are higher by up to one order of magnitude. Taking those groundwater radium activities as typical of the submarine groundwater end-member, a minimum volume of 0.24–4.5 × 1010 l/d is required to support the excess radium isotopes on the inner shelf. This has to be compared with the average rivers water runoff of 15.4 × 1010 l/d during the study period (1.6 to 29% of the river flow). 相似文献
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Coastal groundwater systems can have a considerable impact on sediment transport and foreshore evolution in the surf and swash zones. Process-based modeling of wave motion on a permeable beach taking into account wave-aquifer interactions was conducted to investigate the effects of the unconfined coastal aquifer on beach profile evolution, and wave shoaling on the water table. The simulation first dealt with wave breaking and wave runup/rundown in the surf and swash zones. Nearshore hydrodynamics and wave propagation in the cross-shore direction were simulated by solving numerically the two-dimensional Navier–Stokes equations with a k–ε turbulence closure model and the Volume-Of-Fluid technique. The hydrodynamic model was coupled to a groundwater flow model based on SEAWAT-2000, the latter describing groundwater flow in the unconfined coastal aquifer. The combined model enables the simulation of wave-induced water table fluctuations and the effects of infiltration/exfiltration on nearshore sediment transport. Numerical results of the coupled ocean/aquifer simulations were found to compare well with experimental measurements. Wave breaking and infiltration/exfiltration increase the hydraulic gradient across the beachface and enhance groundwater circulation inside the porous medium. The large hydraulic head gradient in the surf zone leads to infiltration across the beachface before the breaking point, with exfiltration taking place below the breaking point. In the swash zone, infiltration occurs at the upper part of the beach and exfiltration at the lower part. The simulations confirm that beaches with a low water table tend to be accreted while those with a high water table tend to be eroded. 相似文献
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地下水监测及数理分析是地下水动态研究的主要方法。但目前海岸带地区多以陆域地下水监测为主,海域部分尤其具有多层含水层系统的海底地下水缺少直接监测数据。本研究通过海域钻孔ZK03与ZK08实时监测不同层位海底地下水动态以及海洋潮汐变化,结合其地层结构和沉积演化背景,分析莱州湾海底地下水动态特征并揭示其影响机制。研究结果表明,莱州湾海底地下水动态具有周期性和分层性特征;全新世含水层与海水关系密切,其海水入侵界面垂向上厚10 m左右。海底地下水分层与沉积地层划分大致相同,其动态特征是在地层结构及沉积演化环境影响下,降水、径流及潮汐驱动不同层深地下水间或地下水与海水间混合作用的结果。本文初步构建了海底地下水分布模式,探讨区域地下水与海水的相互作用关系。莱州湾海底地下水动态研究对于深入分析海(咸)水界面变化机制及探索海底地下水排泄具有推动作用。 相似文献
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利用三门湾海岸带最近施工完成的水文地质孔、工程地质孔和地下水碳（14C）测年以及前人的分析研究资料,对三门湾海岸带第四系分布、第四系承压含水层富水性和咸淡水资源分布、承压水年龄和可更新能力进行了深入研究。三门湾海岸带蛇盘滩涂围垦区第一承压含水层（组）富水性较好,绝大部分地区为淡水;宁海县长街镇区域承压水淡水资源总体呈“人”字型分布,北部的大湖?车岙港区域淡水主要分布在第一承压含水层（组）中,在大湖?下洋涂区域淡水主要分布在第二承压含水层（组）中。三门湾海岸带第四系承压水年龄普遍较老。蛇盘滩涂围垦区第一承压含水层地下水年龄为21 642～22 012 cal a BP,未受到后期海侵作用影响;长街下洋涂滩涂围垦区第二承压含水层地下水的年龄为35 052～45 439 cal a BP,部分地段受到后期海侵影响。在目前未开采利用条件下,承压水补给条件差、水资源更新性差。对于拟作为应急供水水源地靶区,应加强地下水资源管理。 相似文献
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Priyantha Ranjan So Kazama Masaki Sawamoto Ahmad Sana 《Ocean & Coastal Management》2009,52(3-4):197-206
This paper presents a simplified approach to assess the effects of global warming on global coastal groundwater resources over the next century based on the smallest but necessary number of elements such as rainfall, temperature, hydraulic conductivity of the aquifers, and population changes regarding the consumption of groundwater. The positive aspect in this approach is that there is availability of the above elements in the majority of the planet. Methodology includes a sharp interface concept model and simplified estimation of groundwater recharge using limited climate data. The evaluation shows that the future climate changes would decrease fresh groundwater resources in Central American, South American, South African and Australian regions whereas most of the areas in Asia, except South-East Asia. Combinations of fresh groundwater loss and global population are considered to state the vulnerability of future fresh groundwater supply. Vulnerability assessment shows that South Asia, Central America, North Africa and the Sahara, South Africa and the Middle East countries are highly vulnerable whereas, Northern Europe, Western part of South America, New Zealand and Japan are less vulnerable with respect to future fresh groundwater supply. Further, this paper highlights the necessity Integrated Coastal Management (ICM) practices in these vulnerable coastal regions to ensure the sustainable development in coastal regions. 相似文献
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邱汉学 《中国海洋大学学报(自然科学版)》1993,(Z1)
研究青岛地区玄武岩地质、水文地质条件,提出玄武岩地下水及其含水层(体)的开发途径:干旱年份尽可能多开采地下水,丰水年份人工回灌以增加水资源可利用量。人工回灌的水源可利用大沽河弃水,通过现有井、钻孔及地下隧道进行。 相似文献
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Salinity in a shallow estuary is affected by upland freshwater inputs (surface runoff, stream/canal flows, groundwater), atmospheric processes (precipitation, evaporation), marine connectivity, and wind patterns. In Everglades National Park (ENP) in South Florida, the unique Everglades ecosystem exists as an interconnected system of fresh, brackish, and salt water marshes, mangroves, and open water. For this effort a coastal aquifer conceptual model of the Everglades hydrologic system was used with traditional correlation and regression hydrologic techniques to create a series of multiple linear regression (MLR) salinity models from observed hydrologic, marine, and weather data. The 37 ENP MLR salinity models cover most of the estuarine areas of ENP and produce daily salinity simulations that are capable of estimating 65–80% of the daily variability in salinity depending upon the model. The Root Mean Squared Error is typically about 2–4 salinity units, and there is little bias in the predictions. However, the absolute error of a model prediction in the nearshore embayments and the mangrove zone of Florida Bay may be relatively large for a particular daily simulation during the seasonal transitions. Comparisons show that the models group regionally by similar independent variables and salinity regimes. The MLR salinity models have approximately the same expected range of simulation accuracy and error as higher spatial resolution salinity models. 相似文献
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Field observation was conducted to monitor phosphate concentrations in groundwater and seawater mixing at two sandy beaches in Futtsu and Miura in Tokyo Bay, Japan. Dissolved phosphate concentrations were measured along transects from fresh groundwater aquifer to seawater adjacent the beaches. The concentrations were often high (up to 46 µM) in fresh groundwater samples (Cl– < 0.2). Coastal seawater, on the other hand, exhibited low phosphate concentrations (1.5 µM or less). Along the transects, phosphate generally displayed non-conservative behavior during mixing of fresh and saline waters in the aquifer; concentrations as high as 100 µM were found around the upper limit of seawater intrusion (Cl– = 2). Laboratory experiments were executed to identify the processes that control the phosphate behavior in the mixing processes. The results revealed that adsorption-desorption processes by the aquifer sand particles could significantly control the phosphate concentrations in the groundwater. Furthermore, the adsorption and/or desorption was found to be a function of salinity; the equilibrium concentration of dissolved phosphate in slurry of sand and water was the highest in freshwater and decreased considerably in saline water. The extreme concentration of phosphate may be caused by release from sand particles coinciding with the rapid change in salinity with tide. 相似文献
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基于SPOT6遥感影像的滩涂湿地入侵种互花米草植株高度的反演研究 总被引：1，自引：0，他引：1
本文以SPOT6 高空间分辨率遥感影像为数据源,通过植被覆盖度和地上生物量两个参数进行滩涂湿地入侵种互花米草植株高度的估算研究。结果表明,三沙湾滩涂湿地互花米草植株高度平均值为2.04 m,以1~2 m和2~3 m植株为主要分布高度,分布面积分别为6.83 km2和10.31 km2,占研究区互花米草总面积的33.83%和51.06%,小于1 m和大于3 m的互花米草仅占9.26%和5.84%。估算值与真实值之间的均方根误差为0.204,绝对误差为0.04~0.37 m。该方法是对高空间分辨率光学影像应用研究的重要尝试,其反演方法具有较好的可行性,可较为准确的获取滩涂湿地植株高度信息。 相似文献
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Estimating submarine groundwater discharge at a subtropical river estuary along the Beibu Gulf,China
In certain regions,submarine groundwater discharge(SGD) into the ocean plays a significant role in coastal material fluxes and their biogeochemical cycle;therefore,the impact of SGD on the ecosystem cannot be ignored.In this study,SGD was estimated using naturally occurring radium isotopes(~(223)Ra and ~(224)Ra) in a subtropical estuary along the Beibu Gulf,China.The results showed that the Ra activities of submarine groundwater were approximately 10 times higher than those of surface water.By assuming a steady state and using an Ra mass balance model,the SGD flux in May 2018 was estimated to be 5.98×10~6 m~3/d and 3.60×10~6 m~3/d based on ~(224)Ra and ~(223)Ra,respectively.At the same time,the activities of Ra isotopes fluctuated within a tidal cycle;that is,a lower activity was observed at high tide and a higher activity was seen at low tide.Based on these variations,the average tidal pumping fluxes of SGD were 1.15×10~6 m~3/d and 2.44×10~6 m~3/d with ~(224)Ra and ~(223)Ra,respectively.Tidaldriven SGD accounts for 24%-51% of the total SGD.Therefore,tidal pumping is an important driving force of the SGD in the Dafengjiang River(DFJR) Estuary.Furthermore,the SGD of the DFJR Estuary in the coastal zone contributes significantly to the seawater composition of the Beibu Gulf and the material exchange between land and sea. 相似文献
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莱州湾南岸海水入侵变化趋势及成因分析 总被引：3，自引：2，他引：1
为了探讨滨海经济快速发展形势下莱州湾南岸海水入侵范围变化及其控制因素,利用2011—2015年4月份(枯水期)莱州湾南岸地下水潜水层TDS(可溶性固体总量)、Cl–质量浓度连续监测数据,结合历史资料,分析莱州湾南岸海水入侵分布特征。结果表明,近5年来研究区地下水Cl–质量浓度均值为13.4 g/L,呈由岸向内陆快速减小趋势;研究区海水入侵呈带状分布,2015年入侵线向内陆伸入超过45 km,入侵范围较1980年向陆扩张约11~30 km。通过对比分析得出,研究区年均降雨量、地下水位埋深及地下水超采面积与海水入侵面积呈显著线性相关,发现持续干旱气候、地下淡水超采是导致海水入侵扩张的主要因素,卤水开发、海水养殖及莱州湾沿岸河流拦蓄工程进一步导致海水入侵的加剧。 相似文献
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近岸地下水排泄是近海稀土元素的重要来源,目前对地下水中稀土元素的地球化学行为的认识还十分有限。本文通过现场调查和模拟计算对山东大沽河流域地下水中溶解态稀土元素的分布、影响因素及络合形态进行了研究。结果表明：稀土元素在地下水中的分布具有较大的空间差异,pH和铁锰氧化物/氢氧化物的还原性溶解是影响稀土元素含量的重要因素。稀土元素的络合形态以LnCO+3和Ln(CO3)-2为主,但是在硫酸根含量较高的情况下,轻稀土较中稀土和重稀土更易于形成LnSO+4。大沽河流域地下水表现为重稀土富集,含水层中负电荷颗粒物对LnCO+3的优先吸附可能是富集的原因。受周边炼油厂影响,所有样品中的La均表现为正异常,人为源La在地下淡水和再循环海水中所占比例分别为34%~75%和42%~57%。 相似文献
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P.P. Povinec J. de Oliveira E.S. Braga J.-F. Comanducci J. Gastaud M. Groening I. Levy-Palomo U. Morgenstern Z. Top 《Estuarine, Coastal and Shelf Science》2008
Stable isotopes, tritium, radium isotopes, radon, trace elements and nutrients data were collected during two sampling campaigns in the Ubatuba coastal area (south-eastern Brazil) with the aim of investigating submarine groundwater discharge (SGD) in the region. The isotopic composition (δD, δ18O, 3H) of submarine waters was characterised by significant variability and heavy isotope enrichment. The stable isotopes and tritium data showed good separation of groundwater and seawater groups. The contribution of groundwater in submarine waters varied from a few % to 17%. Spatial distribution of 222Rn activity concentration in surface seawater revealed changes between 50 and 200 Bq m−3 which were in opposite relationship with observed salinities. Time series measurements of 222Rn activity concentration in Flamengo Bay (from 1 to 5 kBq m−3), obtained by in situ underwater gamma-spectrometry showed a negative correlation between the 222Rn activity concentration and tide/salinity. This may be caused by sea level changes as tide effects induce variations of hydraulic gradients, which increase 222Rn concentration during lower sea level, and opposite, during high tides where the 222Rn activity concentration is smaller. The estimated SGD fluxes varied during 22–26 November between 8 and 40 cm d−1, with an average value of 21 cm d−1 (the unit is cm3/cm2 per day). The radium isotopes and nutrient data showed scattered distributions with offshore distance and salinity, which implies that in a complex coast with many small bays and islands, the area has been influenced by local currents and groundwater–seawater mixing. SGD in the Ubatuba area is fed by coastal contaminated groundwater and re-circulated seawater (with small admixtures of groundwater), which claims for potential environmental concern with implications on the management of freshwater resources in the region. 相似文献
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The article deals with deposits exposed in sections along the rivers of the Caspian lowland and on the eastern slope of the Ergenei. The conclusion is made about the lagoonal origin of chocolate clays lying on high-capacity subaerial and alluvial–deltaic deposits. The impact of the Caspian Sea level rise on coastal processes is examined. Taking into account the regularities in the behavior of the coastal zone during sea level rise, subaerial deposits with such thickness in the outcrops could not have been preserved during the early Khvalynian transgression from –100 m. Another curve of Caspian Sea level fluctuations is proposed, where there is no deep Atelian regression between the Khazarian and Khvalynian transgressions. It is concluded that the Khazarian transgression was one of the largest in the history of the Caspian Sea. Its level was slightly less than that of the Khvalynian transgression. The rise of the level of the latter began not from –100 m, but from about 5–15 m; i.e., this transgression was in fact an oscillation of the Caspian Sea against its gradual regression after the Khazarian transgression. Sea level oscillations contributed to the formation of lagoonal-transgressive terraces, in which chocolate clays accumulated.
相似文献18.
Results are reported herein of an open channel flow laboratory based study of the development of ripples on a fine silica sand bed, and under non-uniform turbulent subcritical flow conditions. The hydraulic model used included a diverging channel, which resulted in a variation of hydraulic and sediment transport parameters along the channel. Sediment supply limitation occurred during experimentation, impacting bed form development. The overall aim of this study was to improve the understanding and modelling capability of the development of bed forms under limited sediment supply and non-uniform flow conditions. In particular, the applicability of an existing empirical model capable of predicting ripple development was tested for the conditions of this study, using measured ripple dimensions. The ripple height and length results were extracted from detailed bed profile records, obtained using an acoustic Doppler probe traversed longitudinally over the sediment bed, at various experimentation time intervals. It was found that the non-uniform flow conditions affected the development rate of the bed forms, while sediment supply limitation impacted their steady state dimensions. The measured steady state ripple dimensions were lower, on average, than the corresponding equilibrium dimensions predicted using existing empirical equations. Non-uniform flow also caused the simultaneous occurrence of bed forms at different stages of development along the hydraulic model, where 3D and 2D ripples and incipient bed forms were recorded. Such a scenario can occur in estuarine and coastal flows, due to changing hydraulic conditions and/or a limitation of sediment supply. The ripple development model tested was verified for the conditions of this study, with its accuracy being shown to depend on an accurate determination of steady state parameters. 相似文献
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G. Gnanachandrasamy T. Ramkumar S. Venkatramanan S. Y. Chung S. Vasudevan 《Marine Geophysical Researches》2016,37(2):113-126
We use electrical resistivity data arrayed in a 2715 km2 region with 30 locations to identify the saline water intrusion zone in part of Cauvery deltaic region, offshore Eastern India. From this dataset we are able to derive information on groundwater quality, thickness of aquifer zone, structural and stratigraphic conditions relevant to groundwater conditions, and permeability of aquifer systems. A total of 30 vertical electrode soundings (VES) were carried out by Schlumberger electrode arrangement to indicate complete lithology of this region using curve matching techniques. The electrical soundings exhibited that H and HK type curves were suitable for 16 shallow locations, and QH, KQ, K, KH, QQ, and HA curves were fit for other location. Low resistivity values suggested that saline water intrusion occurred in this region. According to final GIS map, most of the region was severely affected by seawater intrusion due to the use of over-exploitation of groundwater.The deteriorated groundwater resources in this coastal region should raise environmental and health concerns. 相似文献
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Response of Coastal Groundwater Table to Offshore Storms 总被引：1，自引：0，他引：1
Large groundwater table fluctuations were observed in a coastal aquifer during an offshore storm. The storm induced significant changes of the mean shoreline elevation, characterized by a pulse-like oscillation. This pulse propagated in the aquifer, resulting in the water table fluctuations. A general analytical solution is derived to quantify this new mechanism of water table fluctuation. The solution is applied to field observations and is found to be able to predict reasonably well the observed storm-induced water table fluctuations. Based on the analytical solution, the damping characteristics and phase shift of the oscillation as it propagates inland are examined. 相似文献