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1.
Hydrochemical framework of the aquifer in and around East Kolkata Wetlands,West Bengal,India 总被引:1,自引:0,他引:1
The area lies between Hugli river in the northwest and Bidyadhari river in the east and includes the East Kolkata Wetlands.
The East Kolkata Wetlands is included in the List of Wetlands of International Importance (“Ramsar List”), as per the Convention
on Wetlands signed in Ramsar, Iran, in 1971. This wetland has been declared as a Ramsar site on the 19th August 2002 (Ramsar
site no. 1208) and therefore has acquired an international status. The area is a part of the lower deltaic plain of the Bhagirathi–Ganga
river system and is generally flat in nature. The sub-surface geology of the area is completely blanketed by the Quaternary
fluviatile sediments comprising a succession of clay, silty clay, sand and sand mixed with occasional gravel. The Quaternary
aquifer is sandwiched between two clay sequences. The confined aquifer is made up of moderately well sorted sand and reflects
fluviatile environment of deposition. The regional groundwater flow direction is from east to west. Detailed geochemical investigations
of 40 groundwater samples along with statistical analysis (for example, correlation and principal component analysis) on these
chemical data reveal: (i) four types of groundwater quality, for example, good, poor, very poor and water unsuitable for drinking
purpose, (ii) four hydrochemical facies which may be assigned to three broad types such as “fresh”, “blended”, and “brackish”
waters, (iii) the evolution of the “blended” water is possibly due to hydraulic mixing of “fresh” and “brackish” waters within
the aquifer matrix and/or in well mixing, and (iv) absence of Na–Cl facies indicates continuous flushing of the aquifer. 相似文献
2.
Tunisian Chott’s region is one of the most productive artesian basins in Tunisia. It is located in the southwestern part of
the country, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the
water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow
pattern and time of residence. The system is composed of an upper unconfined “Plio-Quaternary” aquifer with a varying thickness
of 20–200 m, an intermediate confined/unconfined “Complex Terminal” aquifer about 100 m in thickness and a deeper “Continental
Intercalaire” aquifer about 150 m in thickness separated by thick clay and marl layers. The dissolution of evaporites and
carbonates explains part of the contained Na+, Ca2+, Mg2+, K+, SO42− and Cl-, but other processes, such carbonate precipitation, also contributes to the water composition. The stable isotope composition
of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient
water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the Plio-Quaternary
aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. 相似文献
3.
The geochemical composition of the terrestrial surface (without soils) and comparison with the upper continental crust 总被引:1,自引:0,他引:1
Jens Hartmann Hans H. Dürr Nils Moosdorf Michel Meybeck Stephan Kempe 《International Journal of Earth Sciences》2012,101(1):365-376
The terrestrial surface, the “skin of the earth”, is an important interface for global (geochemical) material fluxes between
major reservoirs of the Earth system: continental and oceanic crust, ocean and atmosphere. Because of a lack in knowledge
of the geochemical composition of the terrestrial surface, it is not well understood how the geochemical evolution of the
Earth’s crust is impacted by its properties. Therefore, here a first estimate of the geochemical composition of the terrestrial
surface is provided, which can be used for further analysis. The geochemical average compositions of distinct lithological
classes are calculated based on a literature review and applied to a global lithological map. Comparison with the bulk composition
of the upper continental crust shows that the geochemical composition of the terrestrial surface (below the soil horizons)
is significantly different from the assumed average of the upper continental crust. Specifically, the elements Ca, S, C, Cl
and Mg are enriched at the terrestrial surface, while Na is depleted (and probably K). Analysis of these results provide further
evidence that chemical weathering, chemical alteration of minerals in marine settings, biogeochemical processes (e.g. sulphate
reduction in sediments and biomineralization) and evaporite deposition are important for the geochemical composition of the
terrestrial surface on geological time scales. The movement of significant amounts of carbonate to the terrestrial surface
is identified as the major process for observed Ca-differences. Because abrupt and significant changes of the carbonate abundance
on the terrestrial surface are likely influencing CO2-consumption rates by chemical weathering on geological time scales and thus the carbon cycle, refined, spatially resolved
analysis is suggested. This should include the recognition of the geochemical composition of the shelf areas, now being below
sea level. 相似文献
4.
The morphotectonics of the Lower Amur region is controlled by the marginal-continental areal rifting and its interaction with
the general uplifting and moderate tectonic stacking on the margin of the “stable” continent. The marginal-continental rifts
represent an element of the general evolutionary system of forms in the continent-toocean transition zone and morphotectonically
reflect the initial stage of the thinning and transformation of the continental lithosphere. The rim of the stable continent
in the southern Far East is characterized by a complex configuration bordered by large continuous or composite scarps, which
coincide spatially with high-gradient gravity zones. 相似文献
5.
O. A. Bogatikov E. V. Sharkov A. V. Vesselovskii V. B. Mescheryakova 《Doklady Earth Sciences》2009,427(2):907-911
A geographic information system (GIS “Volcanic belts”) was used for analyzing the spatial and temporal relationship between
tectono-magmatic cycles in the Cenozoic that took place at the convergent plate boundaries, mostly in volcanic arc-back-arc
systems. The onset of back-arc basins and subaerial arc volcanism and their main evolutionary stages are shown to have occurred
about the same time. These processes are still ongoing, which is indicated by today’s active volcanoes, high heat flows, and
high deep-focus seismicity. The crust underlying both tectonic structures undergoes transformation, which results in a significant
thinning of the “granite” layer within the volcanic belts, whereas crust within the back-arc basins changes its properties
to the transitional (suboceanic) and oceanic type crusts. All processes that occur at the convergent plate boundaries can
be described within the arc-back-arc system, the principal dynamic components of which are the asthenospheric plume upwelling
above the continent edge and the oceanward-spreading plume head. This was accompanied by a gradual crustal thinning in the
back-arc region and the formation of areas with oceanic crust, as well as by involvement of crustal material, together with
rocks of the subducting slab, into subduction processes. As a result, the continental crust is removed from the tectonosphere
and stored in the “slab cemetery.” Only a minor portion of the crustal materials is returned to the surface as subduction-related
magmatism. 相似文献
6.
Relation of streams, lakes, and wetlands to groundwater flow systems 总被引:24,自引:10,他引:14
Thomas C. Winter 《Hydrogeology Journal》1999,7(1):28-45
Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all
landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts. Although
it generally is assumed that topographically high areas are groundwater recharge areas and topographically low areas are groundwater
discharge areas, this is true primarily for regional flow systems. The superposition of local flow systems associated with
surface-water bodies on this regional framework results in complex interactions between groundwater and surface water in all
landscapes, regardless of regional topographic position. Hydrologic processes associated with the surface-water bodies themselves,
such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of
surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface
water. These processes have been documented at research sites in glacial, dune, coastal, mantled karst, and riverine terrains.
Received, April 1998 · Revised, July 1998, August 1998 · Accepted, September 1998 相似文献
7.
The paper presents a generalized algorithm for the simulation of multiyear cycles in variations of the chemical composition
of lake waters with regard for the seasonal specifics of hydrogeochemical processes. Data were obtained on the behavior of
the hydrogeological system during a time span of 500–1000 years. Each of the simulated model cycles involved a successively
alternating “summer-winter” time periods. Terrestrial exchange fluxes between reservoirs, groundwater inflow, falls of atmospheric
precipitate, and the evaporation of lake water were taken into account for summer periods, whereas winter conditions were
simulated as corresponding to the development of the ice phase, the absence of water exchange fluxes, a change from oxidizing
to reducing conditions, and the burial of solid phases in the sediments. The results of our physicochemical simulations with
the use of data on the composition of natural hydrogeological systems are in good agreement with natural observations and
make it possible to realistically predict the evolution of small lakes in the Ol’khon area. 相似文献
8.
Hydrochemistry and Classification of Groundwater Resources of Ishwardi Municipal Area,Pabna District,Bangladesh 总被引:2,自引:0,他引:2
Golzar Hossain M. Farhad Howladar Lutfun Nessa Syed Samsuddin Ahmed Chowdhury Quamruzzaman 《Geotechnical and Geological Engineering》2010,28(5):671-679
The chemical property of groundwater depends largely on the mineralogical composition of the rocks through which the water
has moved and the rate of movement and these characteristics of surface water depend on organic and inorganic reactions, industrial
effluents, rainfall and temperature etc. The underground water tends to contain more dissolved materials than those in surface
water because of their more intimate and longer contact with organic materials of soil and rock particles. The groundwater
of the studied area is dominant of alkaline earth’s (Ca2+ and Mg2+) and weak acids (HCO3
−) which may be classified as Magnesium-Bicarbonate and Calcium Carbonate types. Genetically, the groundwater of the area belongs
to both “Normal Chloride” “Normal Sulphate” and “Normal Carbonate” to “Super Carbonate” group. Based on EC, SAR and RC, the
groundwater of the area varies from good–excellent quality for irrigation purposes with low alkali hazard and medium salinity
hazard. 相似文献
9.
In this work some examples of “twisting” of the Earth in the geologic past are given: displacement of the northern parts of
the global submeridional structures to the west relative to their southern parts; the rotation of the “geodynamic pair” of
Siberia-Laurentia in the Proterozoic; sinistral displacement of the Northern Hemisphere relative to the Southern Hemisphere
after the collapse of the last Pangaea; the equatorial rotation of the continental plates; oblique orientation of the global
network of planetary fracturing; an inclination of the axis of submeridional compression; sinistral “beveling”; the dextral
“twisting” of Venus. All these examples confirm the idea of possible sinistral “twisting” of the Earth that has been proposed
by many authors. The cause of such “twisting” is unclear, although it is likely connected with the Earth’s rotation around
its axis. Some of these examples show that many paleomagnetic reconstructions can be usefully discussed in a tectonophysical
aspect. Moreover, in connection with this data, the development of a new scientific field, called “paleomagnetic tectonophysics”, is possible. 相似文献
10.
Crustal Composition of China Continent Constrained from Heat Flow Data and Helium Isotope Ratio of Underground Fluid 总被引:2,自引:1,他引:2
Based on conservation of energy principle and heat flow data in China continent, the upper limit of 1.3 μW/m3 heat production is obtained for continental crust in China. Furthermore, using the data of heat flow and helium isotope ratio of underground fluid, the heat productions of different tectonic units in China continent are estimated in range of 0.58–1.12 μW/m3 with a median of 0.85 μW/m3. Accordingly, the contents of U, Th and K2O in China crust are in ranges of 0.83–1.76 μg/g, 3.16–6.69 μg/g, and 1.0%–2.12%, respectively. These results indicate that the abundance of radioactive elements in the crust of China continent is much higher than that of Archean crust; and this fact implies China’s continental crust is much evolved in chemical composition. Meanwhile, significant lateral variation of crustal composition is also exhibited among different tectonic units in China continent. The crust of eastern China is much enriched in incompatible elements such as U, Th and K than that of western China; and the crust of orogenic belts is more enriched than that of platform regions. It can also be inferred that the crusts of eastern China and orogenic belts are much felsic than those of western China and platform regions, respectively, derived from the positive correlation between the heat production and SiO2 content of bulk crust. This deduction is consistent with the results derived from the crustal seismic velocity data in China. According to the facts of the lower seismic velocity of China than the average value of global crust, and the higher heat production of China continent compared with global crust composition models published by previous studies, it is deduced that the average composition models of global continent crust by Rudnick and Fountain (1995), Rudnick and Gao (2003), Weaver and Tarney (1984), Shaw et al. (1986), and Wedepohl (1995) overestimate the abundance of incompatible elements such as U, Th and K of continental crust. 相似文献
11.
Fragments of continental structures in the Indian Ocean 总被引:2,自引:0,他引:2
Yu. M. Pushcharovsky 《Geotectonics》2014,48(1):1-4
Fragments of continental structures (microcontinents) composed of sialic rocks are widespread in the Indian Ocean, where they are located in its African, Australian, and Indian margins. The origin of these fragments is related to splitting off from continent margins along faults and further seaward motion driven by the tectonic flow of mantle masses. 相似文献
12.
13.
Hydrochemical signatures of deep groundwater circulation in a part of the Himalayan foreland basin 总被引:2,自引:1,他引:1
Groundwater samples were analyzed from 71 springs and wells as part of a larger study in a region of compressional tectonic
regime. The study site covers the Peshawar basin and surroundings in the Himalayan foreland of Pakistan. The northern portion
is mountainous and the water table is discontinuous in different intermontane valleys, with abundant springs (with normal
and anomalous temperatures and composition). The southern part is divided into isolated basins with a number of drilled (“deep”)
and dug (“shallow”) wells. Hydrochemical signatures of elevated strontium (Sr), SiO2, boron (B)—and the geothermometric signatures—all indicate a deep circulation of the emerging groundwater. Moreover, for
several of the sample sites, water chemical compositions, measured spring and water well temperatures, and reservoir temperatures
calculated for spring waters, all point to origin from deep horizons within the basin. Remarkable proximity of all the thermal
and hydrochemical anomalies to major faults suggests that the waters ascended along these faults from greater depths. The
area is a natural western extension of the Himalayan Geothermal Belt described in earlier literature for the eastern and central
Himalayas. 相似文献
14.
Silvana Arreghini Laura de Cabo Rafael Seoane Nicolás Tomazin Roberto Serafini Alicia Fabrizio de Iorio 《GeoJournal》2007,70(4):281-288
The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at identifying the dynamics of
water quality in an area with low or “background” concentrations of pollutants within the Reconquista River system in order
to better define levels of pollution in the main system. In order to describe the dynamics of water quality in the background
area, we propose a methodology based on flow estimation with the instantaneous unit hydrograph model and on measurements of
physical and chemical water variables under different hydrological conditions. Because of high dissolved oxygen and low ammonium
and o-phosphate concentrations, the Arroyo Durazno, a tributary stream of the Reconquista River, is defined as a background area. When a storm event begins, the concentration
of nitrates and the electrical conductivity diminish. An increase in dissolved organic carbon suggests an important input
of carbon from hillslope runoff. The proportion of fulvic and humic acids also increases. On the receding limb of the hydrograph,
nitrate concentration was lower than during maximum flow and organic carbon concentration remained high. This behavior, known
as the “flushing effect”, suggests that the soluble material accumulated in the drainage area during dry periods is transported
to the stream by leaching or “lixiviation” and surface runoff, thus raising solute concentrations during the first few hours
of the storm. Water quality changes rapidly, even in background areas, due to its dependence on the flow. The methodology
followed in this paper can also be applied to other basins with similar characteristics. Due to the difficulty in defining
baseline areas for surface waters, a knowledge of background water quality and its dynamics is essential for understanding
pollution trends and anthropogenic impacts on rivers. 相似文献
15.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
16.
A. V. Chuguevskii F. V. Sukhorukov M. S. Mel’gunov I. V. Makarova A. T. Titov 《Doklady Earth Sciences》2010,430(1):51-53
The radioisotope compositions, structure, and behavior of “hot” particles under the natural conditions of the Yenisei River
in the nearby influence zone of Krasnoyarsk mining and chemical combine were examined in this study. By the composition of
gamma-radiating isotopes, all particles are divided into three groups: mono-isotopic, bi-isotopic and poly-isotopic. Mono-isotopic
“hot” particles, containing only 60Co were discovered for the first time. Transuranium elements (241Am and 243Cm) were revealed in poly-isotopic particles. Investigation of poly-isotopic particles by means of a scan electron microscope
showed that the presence of UO2 together with the lack of activation of 152Eu testifies to the reactor origin of this particle. Experiments showed that in natural conditions “hot” particles under the
influence of filtrating water and moisture of pore solutions are gradually dissolved and radionuclides are repeatedly drawn
into migration. 相似文献
17.
The evolution of terrestrial planets (the Earth, Venus, Mars, Mercury, and Moon) was proved to have proceeded according to
similar scenarios. The primordial crusts of the Earth, Moon, and, perhaps, other terrestrial planets started to develop during
the solidification of their global magmatic “oceans”, a process that propagated from below upward due to the difference in
the adiabatic gradient and the melting point gradient. Consequently, the lowest melting components were “forced” toward the
surfaces of the planets in the process of crystallization differentiation. These primordial crusts are preserved within ancient
continents and have largely predetermined their inner structure and composition. Early tectono-magmatic activity at terrestrial
planets was related to the ascent of mantle plumes of the first generation, which consisted of mantle material depleted during
the development of the primordial crusts. Intermediate evolutionary stages of the Earth, Moon, and other terrestrial planets
were marked by an irreversible change related to the origin of the liquid essentially iron cores of these planets. This process
induced the ascent of mantle superplumes of the second generation (thermochemical), whose material was enriched in Fe, Ti,
incompatible elements, and fluid components. The heads of these superplumes spread laterally at shallower depths and triggered
significant transformations of the upper shells of the planets and the gradual replacement of their primordial crusts of continental
type by secondary basaltic crusts. The change in the character of the tectono-magmatic activity was associated with modifications
in the environment at the surface of the Earth, Mars, and Venus. The origin of thermochemical mantle plumes testifies that
the tectono-magmatic process involved then material of principally different type, which had been previously “conserved” at
deep portions of the planets. This was possible only if (1) the planetary bodies initially had a heterogeneous inner structure
(with an iron core and silicate mantle made up of chondritic material); and (2) the planetary bodies were heated from their
peripheral toward central portions due to the passage of a “thermal wave”, with the simultaneous cooling of the outer shells.
The examples of the Earth and Moon demonstrate that the passage of such a “wave” through the silicate mantles of the planets
was associated with the generation of mantle plumes of the first generation. When the “wave” reached the cores, whose composition
was close to the low-temperature Fe + FeS eutectic, these cores started to melt and gave rise to superplumes of the second
generation. The “waves” are thought to have been induced by the acceleration of the rotation of these newly formed planets
due to the decrease of their radii because of the compaction of their material. When this process was completed, the rotation
of the planets stabilized, and the planets entered their second evolutionary stage. It is demonstrated that terrestrial planets
are spontaneously evolving systems, whose evolution was accompanied by the irreversible changes in their tectono-magmatic
processes. The evolution of most of these planets (except the Earth) is now completed, so that they “dead” planetary bodies. 相似文献
18.
黄河源区水环境变化及黄河出现冬季断流的原因 总被引:12,自引:0,他引:12
自1954年有水文观测资料以来,黄河曾在青海省玛多县黄河沿水文站发生过3次断流。本文在分析黄河源区水环境特征及其影响因素的基础上指出,鄂陵湖、扎陵湖的环湖融区调节能力低,当遇到连续干旱、冬季其调节水量不足以维系黄河径流时便会发生断流,这是断流的主因。湖水位降低、开采沙金、过度放牧等自然和人为因素也会对黄河发生断流产生影响。鄂陵湖口附近黄河上修建的水电站开始蓄水,提高了两湖及环湖融区的调节能力,今后黄河冬季出现断流的可能性将大为降低。 相似文献
19.
Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin 总被引:1,自引:1,他引:0
Hans-Jürgen Gawlick Wolfgang Frisch Lirim Hoxha Paulian Dumitrica Leopold Krystyn Richard Lein Sigrid Missoni Felix Schlagintweit 《International Journal of Earth Sciences》2008,97(4):865-881
The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We
dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites,
pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary
cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic
radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment
during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of
the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic
Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides
and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present
position by far-distance west-directed thrusting. 相似文献
20.
A. M. Nikanorov 《Doklady Earth Sciences》2009,429(2):1559-1561
This report gives the conceptual approaches to the development of the theory of the formation of natural water composition
in view of the primary properties of aquatic ecosystems: the “principle of uncertainty” in the estimation of the conditions,
the “continuity” of the changes proceeding, and the “plurality” of water’s natural structure and components (biotic and abiotic),
as well as their interaction processes. The importance and features of each of these basical criteria for characterizing the
conditions of an aquatic ecosystems are substantiated in theory. 相似文献