Occurrence of salt water above fresh water in dynamic equilibrium in a coastal groundwater flow system near De Panne, Belgium     

A. Vandenbohede  L. Lebbe 《Hydrogeology Journal》2006,14(4):462-472

A salt water lens is found above fresh water under the shore between Dunkerque (France) and Nieuwpoort (Belgium). This inverse density distribution is in a dynamic equilibrium. It develops due to the infiltration of salt water on the back shore during high tide. Under this salt water lens, water infiltrated in the adjacent dune area flows towards the sea and discharges at the seabed. This water quality distribution differs from the classic salt water wedge under fresh water described in the literature. Here, the evolution to this water quality distribution is simulated with a density dependent numerical model. A large tidal range, shore morphology and a permeable groundwater reservoir are the main conditions for the observed water quality distribution. By altering these conditions, intermediate water quality distributions between the classic salt water wedge and the one discussed here develop. Based on these simulations, it is expected that similar kinds of inverse density distribution could be present in a number of coastal areas, which have tides, a gently sloping shore and a permeable substratum.  相似文献   

Quantification of karst aquifer discharge components during storm events through end-member mixing analysis using natural chemistry and stable isotopes as tracers   总被引：1，自引：1，他引：1  

Daniel H. Doctor  E. Calvin Alexander Jr  Metka Petrič  Janja Kogovšek  Janko Urbanc  Sonja Lojen  Willibald Stichler 《Hydrogeology Journal》2006,14(7):1171-1191

Karst aquifer components that contribute to the discharge of a water supply well in the Classical Karst (Kras) region (Italy/Slovenia) were quantitatively estimated during storm events. Results show that water released from storage within the epikarst may comprise as much as two-thirds of conduit flow in a karst aquifer following rainfall. Principal components analysis (PCA) and end-member mixing analysis (EMMA) were performed using major ion chemistry and the stable isotopes of water (δ¹⁸O, δ²H) and of dissolved inorganic carbon (δ¹³C_DIC) to estimate mixing proportions among three sources: (1) allogenic river recharge, (2) autogenic recharge, and (3) an anthropogenic component stored within the epikarst. The sinking river most influences the chemical composition of the water-supply well under low-flow conditions; however, this proportion changes rapidly during recharge events. Autogenic recharge water, released from shallow storage in the epikarst, displaces the river water and is observed at the well within hours after the onset of precipitation. The autogenic recharge end member is the second largest component of the well chemistry, and its contribution increases with higher flow. An anthropogenic component derived from epikarstic storage also impacts the well under conditions of elevated hydraulic head, accounting for the majority of the chemical response at the well during the wettest conditions.  相似文献   

The changing relationship between state and church/religion in the Netherlands     

Hans Knippenberg 《GeoJournal》2006,67(4):317-330

The Netherlands is part of the historic Northwest-Southeast multi-confessional culture belt according to the comparative framework of church-state relations in Europe as recently developed by Madeley on the basis of Rokkan’s conceptual map. The aim of this paper is to describe the development of the church-state relations in the Netherlands within this historic framework of state-formation and nation-building, and to interpret recent challenges of its historic state-church model, such as secularisation, the rise of immigrant religions, and general ‘de- and re-territorialisation’ tendencies. The Netherlands developed from a relatively very tolerant polity dominated by the Calvinist Church to a ‘pillarised’ society, in which the Rome-Reformation divide (which also had a strong geographical dimension) was institutionalised in the political system. After the 1960s, very strong secularisation put this ‘pillarised’ system under severe pressure, but the remnants of this system offered a favourable opportunity structure for religious newcomers (Muslims in particular), who could establish their mosques and Muslim schools relatively easily. However, while the main Protestant churches, and even Catholic and Protestant political parties have merged, failing integration of these newcomers in Dutch society and terrorist attacks at the global level as well as in the Netherlands encouraged a new divide between Muslims and non-Muslims. The metropolitan areas in particular became the scene of this new divide.  相似文献   

Calculated Phase Relations in the System Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O with Applications to UHP Eclogites and Whiteschists   总被引：2，自引：0，他引：2  

YANG  JIAN-JUN; POWELL  ROGER 《Journal of Petrology》2006,47(10):2047-2071

Pressure–temperature grids in the system Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O and its subsystems have been calculatedin the range 15–45 kbar and 550–900°C, usingan internally consistent thermodynamic dataset and new thermodynamicmodels for amphibole, white mica, and clinopyroxene, with thesoftware THERMOCALC. Minerals considered for the grids includegarnet, omphacite, diopside, jadeite, hornblende, actinolite,glaucophane, zoisite, lawsonite, kyanite, coesite, quartz, talc,muscovite, paragonite, biotite, chlorite, and plagioclase. Compatibilitydiagrams are used to illustrate the phase relationships in thegrids. Coesite-bearing eclogites and a whiteschist from Chinaare used to demonstrate the ability of pseudosections to modelphase relationships in natural ultrahigh-pressure metamorphicrocks. Under water-saturated conditions, chlorite-bearing assemblagesin Mg- and Al-rich eclogites are stable at lower temperaturesthan in Fe-rich eclogites. The relative temperature stabilityof the three amphiboles is hornblende > actinolite > glaucophane(amphibole names used sensu lato). Talc-bearing assemblagesare stable only at low temperature and high pressure in Mg-and Al-rich eclogites. For most eclogite compositions, talccoexists with lawsonite, but not zoisite, in the stability fieldof coesite. Water content contouring of pressure–temperaturepseudosections, along with appropriate geotherms, provides newconstraints concerning dehydration of such rocks in subductingslabs. Chlorite and lawsonite are two important H₂O-carriersin subducting slabs. Depending on bulk composition and pressure–temperaturepath, amphibole may or may not be a major H₂O-carrier to depth.In most cases, dehydration to make ultrahigh-pressure eclogitestakes place gradually, with H₂O content controlled by divariantor higher variance assemblages. Therefore, fluid fluxes in subductionzones are likely to be continuous, with the rate of dehydrationchanging with changing pressure and temperature. Further, eclogitesof different bulk compositions dehydrate differently. Dehydrationof Fe-rich eclogite is nearly complete at relatively shallowdepth, whereas Mg- and Al-rich eclogites dehydrate continuouslydown to greater depth. KEY WORDS: dehydration; eclogites; phase relations; THERMOCALC; UHP metamorphism; whiteschists  相似文献   

Calculated Phase Relations in the System NCKFMASH (Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O) for High-Pressure Metapelites   总被引：5，自引：0，他引：5  

WEI  CHUNJING; POWELL  ROGER 《Journal of Petrology》2006,47(2):385-408

Petrogenetic grids in the system NCKFMASH (Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O)and the subsystems NCKMASH and NCKFASH calculated with the softwareTHERMOCALC 3.1 are presented for the P–T range 7–30kbar and 450–680°C, for assemblages involving garnet,chloritoid, biotite, carpholite, talc, chlorite, kyanite, staurolite,paragonite, glaucophane, jadeite, omphacite, diopsidic pyroxene,plagioclase, zoisite and lawsonite, with phengite, quartz/coesiteand H₂O in excess. These grids, together with calculated compatibilitydiagrams and P–T and T–X_Ca and P–X_Ca pseudosectionsfor different bulk-rock compositions, show that incorporationof Ca into the NKFMASH system leads to many of the NKFMASH invariantequilibria moving to lower pressure and/or lower temperature,which results, in most cases, in the stability of jadeite andgarnet being enlarged, but in the reduction of stability ofglaucophane, plagioclase and AFM phases. The effect of Ca onthe stability of paragonite is dependent on mineral assemblageat different P–T conditions. The calculated NCKFMASH diagramsare powerful in delineating the phase equilibria and P–Tconditions of natural pelitic assemblages. Moreover, contoursof the calculated phengite Si isopleths in P–T and P–X_Capseudosections confirm that phengite barometry in NCKFMASH isstrongly dependent on mineral assemblage. KEY WORDS: phase relations; metapelites; NCKFMASH; THERMOCALC; phengite geobarometry  相似文献   

利用LPAC图分析北半球夏半年环流季节转换及异常     

蔡新玲王盘兴  杜继稳刘子臣 《南京气象学院学报》2005,28(5):710-716

用NCEP／NCAR再分析月平均风、压场资料得到1958—1997年5—10月月际场的局地型相似系数（LPAC）。多年平均LPAC表明了对流层和平流层低层印度夏季风环流的建立、东亚夏季风环流的北进和南亚高压上高原的过程，这些区域LPAC值较同纬度非季风区明显偏低。在平流层中层，夏季型环流表现出纬向对称性和由高纬向低纬的传播特征。对东亚LPAC气候变率时空剖面及3个涝年LPAC异常的分析反映出环流型季节转变异常及其与东亚月降水异常的关系。  相似文献   

面状目标之间空间拓扑关系的组合式分类   总被引：3，自引：0，他引：3  

郭庆胜  丁虹  刘浩  刘小利 《武汉大学学报(信息科学版)》2005,30(8):728-731

在空间目标拓扑关系组合式描述的基础上,分析了基本空间拓扑关系的组合方法,并根据基本空间拓扑关系,提出了面状目标之间空间拓扑关系的两种分类体系,详细绘制了相应的空间拓扑关系图。  相似文献   

新疆冰雹天气过程的基本特征   总被引：5，自引：0，他引：5  

王旭  马禹 《沙漠与绿洲气象(新疆气象)》2002,25(1):10-11,14

通过对新疆39a冰雹天气资料的普查，得到76次系统性冰雹天气过程和1279次局地冰雹天气过程，局地冰雹天气的发生远远多于系统性雹天气。冰雹天气过程与地形密切相关，主要发生在山区，冰雹天气以1天为主，多发生于夏季，系统性冰雹天气均由中尺度高压造成。  相似文献   

一次秋季局地强降水过程分析     

覃昌柳  黎惠金 《气象研究与应用》2002,23(4):27-29

对常规气象要素、卫星云图和T106物理量诊断产品进行分析,得出2001年10月2～3日发生在桂东南局地强降水成因及中尺度系统特征。  相似文献   

Estimation of azimuth and slowness of tele-seismic signals recorded by a local seismic network     

靳平  潘常周 《地震学报(英文版)》2002,15(6):646-655

Introduction The azimuth and slowness are two major features of seismic signals. The accurate estimation of them is quite important for both phase identification and event location. Generally, there are two types of seismic stations, i.e. 3-component stations (3C) and arrays. To estimate the two direc-tional parameters, the polarization analysis (Jurkevics, 1988) is commonly used for 3C stations and the frequency-wavenumber spectrum analysis ( f-k) (Capon, 1969; Kvaerna, Doornbos, 1986) is …  相似文献