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1.
Natural Hazards - The mixing process of upstream and downstream waters in the dam break flow could generate significant ecological impact on the downstream reaches and influence the environmental... 相似文献
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Hussein A. Amery 《GeoJournal》1998,44(1):19-33
The current location of the border between Lebanon and Palestine, today's Israel, is a product of various competing forces. The Zionist Organization aspired to include the entire Galilee region up to the lower reaches of the Litani River (also known as the Kassimiyah River) within Palestine. The river itself was the desired northern border of the country. The Zionists supported their position by employing instrumental arguments that were largely related to the availability of water resources. On the other hand, residents of the upper Galilee, today's southern Lebanon, demanded that they be included with Lebanon. They used their trade links with Beirut, and cultural and familial ties with other parts of Lebanon to support their position. These instrumental and expressive arguments appear to have assisted in the demarcation of the border between Lebanon and Palestine. Currently, access to the water resources, not necessarily control over them, is likely to influence negotiations between Israel and Lebanon over the future of the Israeli-occupied security zone in southern Lebanon. 相似文献
3.
Acta Geotechnica - This paper presents an experimental investigation of the soil water retention curve (SWRC) and volume change curve over a large suction range (0–286.7 MPa), and... 相似文献
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Homogeneous single crystals of synthetic monticellite with the composition \({\text{Ca}}_{0.88}{\text{Mg}}_{1.12}{\text{SiO}}_4\) (Mtc I) were annealed in a piston-cylinder apparatus at temperatures between 1000 and \(1200\,^{\circ }\hbox {C}\), pressures of 1.0–1.4 GPa, for run durations from 10 min to 24 h and applying bulk water contents ranging from 0.0 to 0.5 wt% of the total charge. At these conditions, Mtc I breaks down to a fine-grained, symplectic intergrowth. Thereby, two types of symplectites are produced: a first symplectite type (Sy I) is represented by an aggregate of rod-shaped forsterite immersed in a matrix of monticellite with end-member composition (Mtc II), and a second symplectite type (Sy II) takes the form of a lamellar merwinite–forsterite intergrowth. Both symplectites may form simultaneously, where the formation of Sy I is favoured by the presence of water. Sy I is metastable with respect to Sy II and is successively replaced by the latter. For both symplectite types, the characteristic spacing of the symplectite phases is independent of run duration and is only weeakly influenced by the water content, but it is strongly temperature dependent. It varies from about 400 nm at \(1000\,^{\circ }\hbox {C}\) to 1200 nm at \(1100\,^{\circ }\hbox {C}\) in Sy I, and from 300 nm at \(1000\,^{\circ }\hbox {C}\) to 700 nm at \(1200\,^{\circ }\hbox {C}\) in Sy II. A thermodynamic analysis reveals that the temperature dependence of the characteristic spacing of the symplectite phases is due to a relatively high activation energy for chemical segregation by diffusion within the reaction front as compared to the activation energy for interface reactions at the reaction front. The temperature dependence of the characteristic lamellar spacing and the temperature-time dependence of overall reaction progress have potential for applications in geo-thermometry and geo-speedometry. 相似文献
6.
Groundwater recharge and evolution of water quality in China’s Jilantai Basin based on hydrogeochemical and isotopic evidence 总被引：1，自引：0，他引：1
Guoxiao Wei Fahu Chen Jinzhu Ma Yang Dong Gaofeng Zhu W. Mike Edmunds 《Environmental Earth Sciences》2014,72(9):3491-3506
We investigated major ions, stable isotopes, and radiocarbon dates in a Quaternary aquifer in semi-arid northwestern China to gain insights into groundwater recharge and evolution. Most deep and shallow groundwater in the Helan Mountains was fresh, with total dissolved solids <1,000 mg L?1 and Cl? <250 mg L?1. The relationships of major ions with Cl? suggest strong dissolution of evaporites. However, dissolution of carbonates, albite weathering, and ion exchange are also the major groundwater process in Jilantai basin. The shallow desert groundwater is enriched in δ18O and intercepts the local meteoric water line at δ18O = ?13.4 ‰, indicating that direct infiltration is a minor recharge source. The isotope compositions in intermediate confined aquifers resemble those of shallow unconfined groundwater, revealing that upward recharge from intermediate formations is a major source of shallow groundwater in the plains and desert. The estimated residence time of 10.0 kyr at one desert site, indicating that some replenishment of desert aquifers occurred in the late Pleistocene and early Holocene with a wetter and colder climate than at present. 相似文献
7.
Thermal diffusivity(D)and thermal conductivity(κ)of harzburgite and dunite from Luobusha ophiolite were simultaneously measured up to 3 GPa and 823 K using the transient plane-source method in a multi anvil apparatus.The results show that the values of D andκof both samples systematically decrease with increasing temperature and increase with increasing pressure.By combination of the thermal physical data of rocks and minerals and geophysical constraints,we performed numerical simulation on the thermal evolution of Tibet vary over depth,distance and geologic ages.The present results provide new constraints on occurrence of partial melting and its geophysical significance beneath Tibetan crust. 相似文献
8.
Zhijun Yao Jian Liu He-Qing Huang Xianfang Song Xiaohui Dong Xin Liu 《Environmental Geology》2009,57(3):551-556
The stable hydrogen and oxygen of lake, river, rain and snow waters were investigated to understand the water cycle characteristics
of the drainage basin of Manasarovar Lake in Tibet. Both δD and δ
18O of river water are larger than those of lake water and the effect of altitude on both δD and δ
18O is not very significant. This phenomenon was suggested to occur because Manasarovar basin is located in Qinghai–Tibet Plateau
which has low latitude, high altitude, abundant glaciers, thin air and intensive solar radiation, resulting in higher evaporation
in lake water. 相似文献
9.
Changes in hydraulic heads with space and time and evolution of the location of fresh water–salt water interface are important
for groundwater development in coastal aquifers. Measurements of piezometric heads at 11 well clusters consisting of three
piezometric wells of different depths with a 5-day interval for 15 months show that the piezometric heads at nearly all the
wells near the northwestern coast in Beihai decrease with increasing depth and increase with increasing distance from the
coast. Changes in piezometric heads at the wells during the measurement period were caused by seasonal precipitation and induced
by the tide. The depth of the sharp interface between fresh water–salt water can be estimated based on measurements of piezometric
heads at a piezometric well tapping at a point in the salt water zone below the interface and measurements of the water table
at the same well. The calculations of the interface for well H5 range from 40 to 80 m below sea level in the measurement period,
which are believed to be more reasonable than those estimated with the Ghyben–Herzberg relation.
An erratum to this article can be found at 相似文献
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The paper presents the results of an experimental study on the effects of the initial water content and dry density on the
soil–water retention curve and the shrinkage behavior of a compacted Lias-clay. The initial conditions after compaction (initial
water content and initial dry density) have been chosen on the basis of three Proctor tests of different compaction efforts.
According to the eight chosen initial conditions clay samples have been compacted statically. The relation between total suction
and water content was determined for the drying path starting from the initial conditions without previous saturation of the
specimens. A chilled-mirror dew-point hygrometer was used for the suction measurements. For the investigation of the shrinkage
behavior cylindrical specimens were dried to desired water contents step-by-step without previous saturation. The volume of
the specimens was measured by means of a caliper. Based on the test results the influence of different initial conditions
on the soil suction and the shrinkage behavior is analyzed. The soil–water retention curves obtained in terms of the gravimetric
water content are independent of the initial dry density. At water contents above approximately 11–12.5% a strong influence
of the compaction water content is observed. At smaller water contents, the soil–water retention curve is independent of the
compaction water content. The results of the shrinkage tests show that the influence of the compaction dry density on the
shrinkage behavior is negligible. Similar to the drying behavior of saturated samples a primary and a residual drying process
could be distinguished. The primary drying process is strongly influenced by the initial water content. In contrast, the rate
of the volume change of the residual drying process is unaffected by the initial water content. 相似文献
12.
The incorporation of OH defects in quartz from the systems quartz–water, quartz–albite–water and granite–water at pressures between 5 and 25?kbar and temperatures between 800 and 1,000?°C was investigated by IR spectroscopy. The two most important OH absorption features can be assigned to hydrogarnet defects (absorption band at 3,585?cm?1) and coupled substitutions involving Al3+ (Al–H defects, absorption bands at 3,310, 3,378 and 3,430?cm?1). Al incorporation in quartz is controlled by mineral/melt partitioning (D Al Qz/Melt ?=?0.01) and exhibits a negative pressure dependence. This trend is not clearly reflected by the concentration of Al–H defects, which shows positive deviations from the theoretical 1:1 correlation of Al/H for some samples. In contrast to the Al–H defects, formation of hydrogarnet defects appears to be positively correlated to pressure and water activity, and may be used a petrological indicator. The overall water concentration exhibits only minor changes with pressure and temperature, but a clear correlation of water activity (controlled by various amounts of dissolved salts) and hydrogarnet substitution could be established. 相似文献
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Peter Birkle Bernardo Martínez García Carlos M. Milland Padrón Bruce M. Eglington 《Applied Geochemistry》2009
The chemical and isotopic characterization of formation water from 18 oil production wells, extracted from 5200 to 6100 m b.s.l. at the Jujo–Tecominoacán carbonate reservoir in SE-Mexico, and interpretations of historical production records, were undertaken to determine the origin and hydraulic behavior of deep groundwater systems. The infiltration of surface water during Late Pleistocene to Early Holocene time is suggested by 14C-concentrations from 2.15 to 31.86 pmC, and by 87Sr/86Sr-ratios for high-salinity formation water (0.70923–0.70927) that are close to the composition of Holocene to modern seawater. Prior to infiltration, the super-evaporation of seawater reached maximum TDS concentrations of 385 g/L, with lowest δ18O values characterizing the most hypersaline samples. Minor deviations of formation water and dolomite host rocks from modern and Jurassic 87Sr/86Sr-seawater composition, respectively, suggest ongoing water–rock interaction, and partial isotopic equilibration between both phases. The abundance of 14C in all sampled formation water, 87Sr/86Sr-ratios for high-salinity water close to Holocene – present seawater composition, a water salinity distribution that is independent of historic water-cut, and a total water extraction volume of 2.037 MMm3 (1/83–4/07) excludes a connate, oil-leg origin for the produced water of the Jurassic–Cretaceous mudstone-dolomite sequence. Temporal fluctuations of water chemistry in production intervals, the accelerated migration of water fronts from the reservoir flanks, and isotopic mixing trends between sampled wells confirms the existence of free aquifer water below oil horizons. Vertical and lateral hydraulic mobility has probably been accelerated by petroleum extraction. 相似文献
14.
《International Geology Review》2012,54(10):1202-1219
We report results of laser ablation inductively coupled plasma-mass spectrometry-based dating, as well as the analysis of bulk-rock major and trace elements, and Sr–Nd isotopes to address the genesis and tectonic settings of the Yanshanian granitoids in neighbouring sections of Zhejiang, Jiangxi, and Anhui provinces (the WZG region) within the Yangtze block. Geochronological results indicate that intense magmatic activity took place during Jurassic to Cretaceous time in the WZG region. Three episodes can be clearly distinguished by their bulk-rock geochemistry. (1) Early–Middle Jurassic granitoids (180–170 Ma) have high Sr and low Yb content, high ?Nd(t) and low initial 87Sr/86Sr ratios, and weakly negative Eu anomalies. These granitoids are strongly enriched with LREE, Rb, K, and Th but are depleted of HREE, Nb, and Ta. (2) Late Jurassic to Early Cretaceous granitoids (165–140 Ma) have relatively low Sr and low Yb contents, as well as low ?Nd(t) and high initial 87Sr/86Sr ratios, with characteristics similar to those of the Early–Middle Jurassic granitoids in terms of the rare earth element and trace element patterns. (3) Early Cretaceous granitoids (140–120 Ma) have extremely low Sr and high Yb concentrations, as well as high SiO2 but low MgO, CaO, and Al2O3 content, with strong negative anomalies in Eu, Ba, Sr, P, and Ti. These characteristics indicate that the WZG Jurassic granitoids were related to northwestward subduction of the Izanagi plate, whereas the Early Cretaceous granitoids formed in a within-plate extensional setting. The time of transition between the two tectonic environments can be constrained to ～140 Ma. This tectonic transition may be attributed to progressive slab roll-back of the Izanagi plate. The presence of two A-type granite belts in the WZG region probably reflects lithospheric thinning. The NE trend of the A-type granite belts indicates that this extension in Southeast China was controlled by underflow of the Izanagi plate. 相似文献
15.
Water samples from precipitation, glacier melt, snow melt, glacial lake, streams and karst springs were collected across SE
of Kashmir Valley, to understand the hydrogeochemical processes governing the evolution of the water in a natural and non-industrial
area of western Himalayas. The time series data on solute chemistry suggest that the hydrochemical processes controlling the
chemistry of spring waters is more complex than the surface water. This is attributed to more time available for infiltrating
water to interact with the diverse host lithology. Total dissolved solids (TDS), in general, increases with decrease in altitude.
However, high TDS of some streams at higher altitudes and low TDS of some springs at lower altitudes indicated contribution
of high TDS waters from glacial lakes and low TDS waters from streams, respectively. The results show that some karst springs
are recharged by surface water; Achabalnag by the Bringi stream and Andernag and Martandnag by the Liddar stream. Calcite
dissolution, dedolomitization and silicate weathering were found to be the main processes controlling the chemistry of the
spring waters and calcite dissolution as the dominant process in controlling the chemistry of the surface waters. The spring
waters were undersaturated with respect to calcite and dolomite in most of the seasons except in November, which is attributed
to the replenishment of the CO2 by recharging waters during most of the seasons. 相似文献
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Huang Jinbai Wen Jiawei Hinokidani Osamu Yasuda Hiroshi 《Environmental Earth Sciences》2014,72(9):3623-3633
The objectives of this study were to examine the runoff characteristics and to estimate water budget at the wind–water erosion crisscross region on the Loess Plateau of China. A small catchment known as Liudaogou that has representative meteorological and hydrological conditions of the wind–water erosion crisscross region was chosen as the study location. A numerical model for rainfall-runoff was developed and verified; rainfall-runoff calculation for 5 years (2005–2009) was performed. The observed data and numerical result of the surface runoff were used for evaluating runoff characteristics and estimating the annual water budget. Runoff rate was proportional to average intensity of rain. Even though rainfall duration was for few minutes, surface runoff was generated by intensity of more than 2.6 mm × 5 min?1, when rainfall duration exceeded 10 h; surface runoff was generated by an intensity of 0.6 mm × 5 min?1, while annual runoff rate was 10–15 %. The unit area of 1 km2 was adopted as the index area for estimating annual water budget. Runoff, evapotranspiration, variation of water storage, and habitant water consumption accounted for 20.4, 75.6, 0, and 4 % of the total annual precipitation, respectively. Results of this study provide the basis for further research on hydrology, water resources, and sustainable water development and utilization at the wind–water erosion crisscross region on the northern Loess Plateau where annual water resources are relatively deficient. 相似文献
18.
As one of the largest copper–molybdenum (Cu–Mo) mines in the world, the Erdenet Mine in Mongolia has been active since 1978 and is expected to continue operations for at least another 30 years. In this study, the potential impacts of mining activities on the soil and water environments have been evaluated. Water samples showed high concentrations of sulfate, calcium, magnesium, Mo, and arsenic, and high pH values in the order of high to low as follows: tailing water > Khangal River > groundwater. Statistical analysis and the δ2H and δ18O values of water samples indicate that the tailing water directly affects the stream water and indirectly affects groundwater through recharge processes. Soil and stream sediments are highly contaminated with Cu and Mo, which are major elements of ore minerals. Based on the contamination factor (CF), the pollution load index (PLI), and the degree of contamination (Cd), soil appears to be less contaminated than stream sediments. The soil particle size is similar to that of tailing materials, but stream sediments have much coarser particles, implying that the materials have different origins. Contamination levels in stream sediments display a tendency to decrease with distance from the mine, but no such changes are found in soil. Consequently, soil contamination by metals is attributable to wind-blown dusts from the tailing materials, and stream sediment contamination is caused by discharges from uncontained subgrade ore stock materials. Considering the evident impact on the soil and water environment, and the human health risk from the Erdenet Mine, measures to mitigate its environmental impact should be taken immediately including source control, the establishment of a systematic and continuous monitoring system, and a comprehensive risk assessment. 相似文献
19.
《Geodinamica Acta》2002,15(4):209-231
Along the Periadriatic Lineament in the Alps and the Sava–Vardar Zone of the Dinarides and Hellenides, Paleogene magmatic associations form a continuous belt, about 1700 km long. The following magmatic associations occur: (1) Eocene granitoids; (2) Oligocene granitoids including tonalites; (3) Oligocene shoshonite and calc-alkaline volcanics with lamprophyres; (4) Egerian–Eggenburgian (Chattian) calc-alkaline volcanics and granitoids. All of these magmatic associations are constrained by radiometric ages, which indicate that the magmatic activity was mainly restricted to the time span between 55 and 29 Ma. These igneous rocks form, both at surface and in the subsurface, the distinct linear Periadriatic–Sava–Vardar magmatic belt, with three strikes that are controlled by the indentation of Apulia and Moesia and accompanying strike-slip faulting. The geology, seismicity, seismic tomography and magnetic anomalies within this belt suggest that it has been generated in the African–Eurasian suture zone. Based on published analytical data, the petrology, major and trace element contents and Sr, Nd and O isotopic composition of each magmatic association are briefly defined. These data show that Eocene and Oligocene magmatic associations of the Late Paleogene Periadriatic–Sava–Vardar magmatic belt originated along a consuming plate margin. Based on isotopic systems, two main rock groups can be distinguished: (1) 87Sr/86Sr = 0.7036–0.7080 and δ18O = 5.9–7.2‰, indicating basaltic partial melts derived from a continental mantle–lithosphere, and (2) 87Sr/86Sr = 0.7090–72131 and δ18O = 7.3–11.5‰, indicating crustal assimilation and melting. The mantle sources for the primary basalt melts are metasomatized garnet peridotites and/or spinel lherzolites and phlogopite lherzolites of upper mantle wedge origin. The geodynamic evolution of the plutonic and volcanic associations of the Periadriatic–Sava–Vardar magmatic belt was related to the Africa–Eurasia suture zone that was dominated by break-off of the subducted lithospheric slab of Mesozoic oceanic crust, at depths of 90–100 km. This is indicated by their contemporaneity along the 1700 km long belt. 相似文献
20.
U–Pb–Hf of detrital zircons from diverse Cambrian units in Morocco and Sardinia were investigated in order to clarify the sandstone provenance and how it evolved with time, to assess whether the detrital spectra mirror basement crustal composition and whether they are a reliable pointer on the ancestry of peri-Gondwanan terranes. Coupled with Hf isotopes, the detrital age spectra allow a unique perspective on crustal growth and recycling in North Africa, much of which is concealed below Phanerozoic sediments.In Morocco, the detrital signal of Lower Cambrian arkose records local crustal evolution dominated by Ediacaran (0.54–0.63 Ga) and Late-Paleoproterozoic (1.9–2.2 Ga; Eburnian) igneous activity. A preponderance of the Neoproterozoic detrital zircons possess positive εHf(t) values and their respective Hf model ages (TDM) concentrate at 1.15 Ga. In contrast, rather than by Ediacaran, the Neoproterozoic detrital signal from the Moroccan Middle Cambrian quartz-rich sandstone is dominated by Cryogenian-aged detrital zircons peaking at 0.65 Ga alongside a noteworthy early Tonian (0.95 Ga) peak; a few Stenian-age (1.0–1.1 Ga) detrital zircons are also distinguished. The majority of the Neoproterozoic zircons displays negative εHf(t), indicating the provenance migrated onto distal Pan-African terranes dominated by crustal reworking. Terranes such as the Tuareg Shield were a likely provenance. The detrital signal of quartz–arenites from the Lower and Middle Cambrian of SW Sardinia resembles the Moroccan Middle Cambrian, but 1.0–1.1 Ga as well as ~ 2.5 Ga detrital zircons are more common. Therefore, Cambrian Sardinia may have been fed from different sources possibly located farther to the east along the north Gondwana margin. 1.0–1.1 Ga detrital zircons abundant in Sardinia generally display negative εHf(t) values while 0.99–0.95 Ga detrital zircons (abundant in Morocco) possess positive εHf(t), attesting for two petrologically-different Grenvillian sources. A paucity of detrital zircons younger than 0.6 Ga is a remarkable feature of the detrital spectra of the Moroccan and Sardinian quartz-rich sandstones. It indicates that late Cadomian orogens fringing the northern margin of North Africa were low-lying by the time the Cambrian platform was deposited. About a quarter of the Neoproterozoic-aged detrital zircons in the quartz-rich sandstones of Morocco (and a double proportion in Sardinia) display positive εHf(t) values indicating considerable juvenile crust addition in North Africa, likely via island arc magmatism. A substantial fraction of the remaining Neoproterozoic zircons which possess negative εHf(t) values bears evidence for mixing of old crust with juvenile magmas, implying crustal growth in an Andean-type setting was also significant in this region. 相似文献