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为了解不同水位变化影响下的河水与地下水侧向交互带地球化学特征动态,以重庆市马鞍溪为研究对象,选取丰水期向枯水期过渡的10-12月为研究期,对河水、地下水及交互带的水位、水温、溶解氧(DO)、pH值、电导率(EC)进行监测,结合对水体主要离子浓度的分析。结果表明,随枯水期到来,侧向交互带水位发生较大变化,交互带与河水间的水位梯度缩小,河水入渗动力逐渐减弱。水位的变化及入渗水温的降低,使交互带微生物活动减弱,pH值上升且变幅减小,DO上升。在其影响下,交互带EC下降,变幅减小,交互带对NO3-、SO42-的净化能力降低,对Mn、Zn等重金属固定能力增强。通过分析交互带地球化学特征的变化,可推断出随马鞍溪枯水期的到来,侧向交互带边界由距河岸30~50 cm移动至距河岸30 cm以内。 相似文献
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《Applied Geochemistry》1999,14(3):333-363
The hydrochemical, radiochemical, stable isotope, 14C and dissolved noble gas composition of groundwaters has been determined along two profiles across the confined, fissured Chalk aquifer of the London Basin of southern England, and for selected sites in the adjacent Berkshire Basin. During downgradient flow in the London Basin aquifer, the groundwater chemistry is modified by water–rock interactions: congruent and incongruent reaction of the carbonate lithology resulting in enhanced Mg/Ca and Sr/Ca ratios and 13C contents with increased residence times; redox and ion exchange reactions; and towards the centre of the Basin, mixing with a residual saline connate water stored in the Chalk matrix. There is evidence from anomalous water chemistries for a component of vertical leakage from overlying Tertiary beds into the confined aquifer as a result of historical dewatering of the aquifer. Dissolved noble gas contents indicate the climate was up to 4.5°C cooler than at present during recharge of the waters now found in the centres of both Basins; stable isotope (2H and 18O) depletions correspond to this recharge temperature change. For evolved waters having δ13C > −8‰ PDB a negative linear correlation is demonstrated between derived recharge temperatures and δ13C values, which is interpreted as mixing between relatively warm, light isotopic, fracture-borne waters and cooler stored waters of the matrix having a 13C signature more or less equilibrated with the Chalk. From geochemical (14C, 4He) age estimates, the abstracted water is interpreted as being either of wholly Holocene/post-Devensian glacial origin, or an admixture of Holocene and Late Pleistocene pre-glacial (cold stage interstadial) recharge. Devensian pleniglacial stage waters of the Last Glacial Maximum are not represented. 相似文献
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Frank Dennis John N. Andrews Andrew Parker Jason Poole Manfred Wolf 《Applied Geochemistry》1997,12(6):763-773
The chemical and isotopic composition of groundwater from 52 sites in the London (U.K.) area was determined as part of a project aimed at assessing the spatial variation in the age of Chalk groundwater, and in determining the relationship between fracture and matrix groundwater in this dual porosity system.Systematic changes in groundwater chemistry take place in the downgradient direction in response to several chemical processes. These processes include early concentration by evaporation and congruent dissolution of calcite followed by widespread incongruent dissolution and ion exchange in addition to local oxidation-reduction reactions, gypsum dissolution and saline intrusion. As a result of the above processes, Chalk groundwater follows an evolutionary path from Ca bicarbonate type to Na bicarbonate type.The age of Chalk groundwater was modelled using14C, δ13C,3H, δ2H and δ180. There is a general increase in the groundwater age in a downgradient direction with the oldest water found in N central areas of the basin. Groundwater in the unconfined zones and in areas S of the Greenwich fault is almost entirely of unevolved, modem composition. Carbon-14 modelling suggests that Chalk groundwater in the S basin is generally less than 10000 a old while that in the north is generally between 10000 and 25000 a old. The presence of3H in concentrations of up to 7 TU in groundwater which yields ages of several 1000 a, however, indicates that mechanisms exist for the rapid introduction of recent groundwater to the confined aquifer. Results of palaeorecharge temperature determinations using δ2H, δ180 and noble gas analytical results suggest that significant Devensian recharge did indeed occur in the aquifer.A model of the development of the Chalk recognizes that it is a classic dual porosity aquifer in which groundwater flow occurs predominantly in the fracture system. The upper 50 m of the aquifer was flushed with fresh water during the 2–3 × 106 a of the Quaternary and therefore meteoric water largely replaced the Tertiary and Cretaceous marine water that previously saturated the system. Most processes which control the chemistry of the groundwater occur in the matrix where the surface area is exceptionally high. Although fracture flow dominates the flow regime, diffusion from the matrix into the fracture porosity controls the chemistry of Chalk groundwater. 相似文献
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《Applied Geochemistry》1998,13(1):3-16
The storage of low level radioactive waste in trenches overlying an unconfined groundwater flow system in sands has generated a contaminant plume (with chemical characteristics of dilute sanitary landfill leachate) containing 14C both as dissolved inorganic and organic C. In the groundwater, dissolved organic compounds account, on average, for 22% of the total C and 10% of the 14C. Approximately 300 m from the waste management site, the groundwater discharges to the surface in a wetland containing up to 3 m of peat and an extensive tree cover. Drainage from the wetland passes through a gauged stream. Radiocarbon input to the groundwater discharge area in 1991 was determined to be between 3.3 and 4.2 GBq, based on data from a line of sampling wells along the groundwater input boundary of the wetland, with control provided by water and tritium balance data. During the 1991 study year, only 1.5–2% of both the inorganic and organic 14C inputs left the wetland in surface water drainage. Vegetation growth in the wetland during the study year contained 8–10% of the released radiocarbon. If the rate of 14C accumulation in the peat has been constant, 7–9% of the annual radiocarbon input has been retained in the organic soil. Much of this soil accumulation can be attributed to litter from standing vegetation, making distribution coefficients an inappropriate model for 14C partitioning between groundwater and soil. The plant/soil 14C concentration ratio was 24 to 33, but application of a concentration ratio to describe the transfer of radiocarbon to plants is also believed to be inappropriate. This study indicates that over 80% of the groundwater radiocarbon is rapidly lost to the atmosphere when the groundwater comes to surface, and we infer that most of the 14C accumulation in vegetation occurs by CO2 transfer from the air to the plant. 相似文献
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The stable isotopes of oxygen and hydrogen were used to determine the seasonal contributions of precipitation to groundwater
recharge at a forested catchment area in the upper North Han River basin, Korea. A comparison of the stable isotopic signatures
of groundwater and precipitation indicates that the precipitations which occurred during both the dry and rainy seasons are
the important source of groundwater recharge in this region. A stable isotopic signature shown in the stream waters at the
upstream reaches is similar to that of groundwaters, indicating that stream waters are mostly fed by groundwater discharge.
Reservoir waters in the downstream flood control dams have lower deuterium excess values or d-values compared with those of the upstream waters, indicating a secondary evaporative enrichment. These results can provide
a basis for the effective management of groundwater and stream water resources in the North Han River basin. 相似文献
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The Himalayas are one of the largest cryospheric systems outside the Polar Regions, and include more than 12,000 glaciers spread over an area of about 33,000 km2. The Himalayan glaciers and snow packs retreating at an accelerating rate, thereby creating an alarming situation for the huge population that resides in northwestern India and southeastern Pakistan, as they depend on surface water resources in the region and rivers emanating from the Himalayas. This work attempts to quantify the contribution of different sources such as glacial/ice/snow melt and groundwater discharge to the Satluj River using the stable isotopes based hydrograph separation method at Ropar (foot hill) and Yusufpur in plain of Punjab, India. A mass balance model of three-component mixing has been engaged using the values of δ18O and electrical conductivity of the river water, and its discharge fraction, to estimate the time-varying relative proportion of each component from July 2013 to January 2014. The proportion of glacier melt was found to peak up to ~?64% at Ropar and ~?15% at Yusufpur during the wet summer months. The fraction of groundwater discharge was found to vary between 10–20% at Ropar and 25–35% at Yusufpur (Punjab plain) over time. The observed trend of d-excess (deuterium excess) values of river water also suggests that the glaciers and snow packs at higher altitudes contain a significant fraction of snow derived from vapor originating in the Mediterranean region, driven by the mid-latitude westerlies known as western disturbances. 相似文献
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Wei Xu Xiaosi Su Zhenxue Dai Fengtian Yang Pucheng Zhu Yong Huang 《Hydrogeology Journal》2017,25(7):2015-2029
Environmental tracers (such as major ions, stable and radiogenic isotopes, and heat) monitored in natural waters provide valuable information for understanding the processes of river–groundwater interactions in arid areas. An integrated framework is presented for interpreting multi-tracer data (major ions, stable isotopes (2H, 18O), the radioactive isotope 222Rn, and heat) for delineating the river–groundwater interactions in Nalenggele River basin, northwest China. Qualitative and quantitative analyses were undertaken to estimate the bidirectional water exchange associated with small-scale interactions between groundwater and surface water. Along the river stretch, groundwater and river water exchange readily. From the high mountain zone to the alluvial fan, groundwater discharge to the river is detected by tracer methods and end-member mixing models, but the river has also been identified as a losing river using discharge measurements, i.e. discharge is bidirectional. On the delta-front of the alluvial fan and in the alluvial plain, in the downstream area, the characteristics of total dissolved solids values, 222Rn concentrations and δ18O values in the surface water, and patterns derived from a heat-tracing method, indicate that groundwater discharges into the river. With the environmental tracers, the processes of river–groundwater interaction have been identified in detail for better understanding of overall hydrogeological processes and of the impacts on water allocation policies. 相似文献
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河流与地下水的脱节现象广泛存在于干旱及半干旱地区,二者间的相互作用已成为目前的研究热点。在简要分析河流与地下水关系的基础上,综述了河流与含水层之间由饱和连接,经过渡脱节,演化为完全脱节系统的物理过程及机理和脱节系统形成的必要条件。总结分析了最大渗漏量法、临界地下水位法、水位波动法等河流与地下水关系判别方法以及优缺点。讨论了非稳定演化过程中河水的入渗规律以及介质时空非均质性对脱节系统的影响。分析认为目前脱节形成机理仍不完全明晰;简便有效的判别方法还需进一步研究;介质时空非均质性对河水渗漏的影响是未来研究的重要方向。 相似文献
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The irreversible water–rock mass exchanges leading to the production of the Fiume Grande valley (Calabria, Italy) stream waters
and groundwaters, starting from local rainwaters, were simulated through reaction path modeling in reaction progress (stoichiometric)
mode. The simulations assumed bulk dissolution of a phyllitic rock and calcite and precipitation of gibbsite, kaolinite, amorphous
silica, illite, a smectite solid mixture, a hydroxide solid mixture, and a trigonal carbonate solid mixture. The analytical
contents of major and trace elements in stream waters and groundwaters were satisfactorily reproduced. However, further investigations
are necessary to clarify the fate of As in this natural systems.
相似文献
Rosanna De RosaEmail: |
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A meander lobe neck diverts stream water into a hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic processes have been well-documented in surface water–groundwater mixing zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the hyporheic zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with seasonal temperature variation. Together, the pressure and temperature data indicate that water moves across the meander neck. The inflow of stream water through the meander neck suggests that the meander system may host biogeochemical hyporheic zone processes. 相似文献
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Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.–Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0–2 m depth) to reducing (2–5 m depth) then suboxic conditions (5–7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n = 7) and sediment (n = 11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ∼700 mg kg−1) is associated with the suboxic zones mostly between 0 and 2 m depth and less frequently between 5 and 7 m depth. The As enriched zones consist of several 5–10 cm-thick dispersed layers and span a length of ∼5–15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6 ± 11.7 mg L−1) and As (118 ± 91 μg L−1, mostly as arsenite) between 2 and 5 m depth, but lower concentrations between 0 and 2 m depth (0.13 ± 0.19 mg L−1 Fe, 1 ± 1 μg L−1 As) and between 5 and 6 m depth (1.14 ± 0.45 mg L−1 Fe, 28 ± 17 μg L−1 As). Because it would take more than a few hundred years of steady groundwater discharge (∼10 m yr−1) to accumulate hundreds of mg kg−1 of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer. 相似文献
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J. A. Ramos Leal C. Noyola Medrano F. O. Tapia Silva J. T. Silva García L. R. Reyes Gutiérrez 《Hydrogeology Journal》2012,20(3):591-603
Aquifer systems present intrinsic properties such as vulnerability, which is identified as the potential risk of groundwater pollution by contaminants generated by human activity. When there are surface sources of pollution, usually there is a direct relationship between high vulnerability and decreased water quality. Nevertheless, this relationship is not observed in all aquifers and so the causative circumstances of inconsistencies between aquifer vulnerability and water quality have been investigated. This work addresses the vulnerability assessment of the Chapala Marsh area, Mexico, using SINTACS analysis. The Chapala Marsh aquifer is characterized by a granular structure and a fractured recharge zone; there are natural and anthropogenic sources of pollution. The results show discrepancies between the vulnerability indices and groundwater quality, as indicated by the existence of vulnerable areas with good water quality and vice versa. This is because the SINTACS method works well when contaminants have only vertical movement. For scenarios with lateral movement of contaminants, the method of geographic weighted regression (GWR) is used to model the influence of potential sources of contaminants on the water quality. 相似文献
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Geochemical investigation of groundwater in a Granitic Island: a case study from Kinmen Island,Taiwan 总被引:1,自引:0,他引:1
Tai-Sheng Liou Hsueh-Yu Lu Cheng-Kuo Lin Wayne Lin Yu-Te Chang Jeng-Ming Chien Wen-Fu Chen 《Environmental Geology》2009,58(7):1575-1585
Kinmen Island is principally composed of low permeable granitoid and covered by a very thin sedimentary layer. Both surface
and groundwater resources are limited and water demand is increasing with time. The groundwater in the granitoid has been
surveyed as an alternative water source for daily use. Two to five highly fractured zones in the granitoid aquifer for each
site were first determined by geochemical well logging. Accordingly, ten samples were collected from three sites. Using environmental
isotopes and geochemical modeling, geochemical processes occurring due to water–rock interaction in the granitoid aquifer
can be quantitatively interpreted. The stable isotopes of oxygen and hydrogen in groundwaters cluster along Taiwan’s local
meteoric waterline, indicating evaporation does not have considerable effect on groundwaters. Given such a high evaporation
rate for Kinmen Island, this result implies that infiltration rate of groundwater is high enough to reduce retention time
through a well-developed fracture zone. NetpathXL is employed for inverse geochemical modeling. Results determine gypsum as
being the major source of sulfate for deep groundwaters. The contribution from pyrite is minor. In addition, the weathering
of albite to kaolinite is the dominant water–rock interaction characterizing geochemical compositions of deep groundwater
in Kinmen Island. 相似文献
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《Applied Geochemistry》1987,2(1):81-91
Calcite is a common fracture inflilling mineral in the Grenville gneisses of the Chalk River area, Ontario, Canada. It exhibits a variety of occurrences and textures which suggests calcite has precipitated under different hydrogeochemical conditions that may be identified through a detailed chemical and isotopic investigation of the calcite and associated infilling minerals.The δ18O of these calcites range over 20%. but the δ13C varies over a narrow range of 5%.. None of the calcites analyzed is in isotopic equilibrium with both the δ18O and δ13C of the present day ground water. The lightest δ18O calcites (near 0%. SMOW) are present in sealed fractures and are sometimes associated with laumontite. This suggests that these light calcites formed from hydrothermal solutions (at temperatures less than about 300°C) shortly after the period of metamorphism that formed the gneisses. This interpretation is supported by relatively unradiogenic87Sr/86Sr ratios near 0.709 and δ13C values of −5 to −6%..Most of the Chalk River calcites, however, are considerably heavier in18O and lighter in13C than the hydrothermal end member. This may be the result of low temperature recrystallization of the hydrothermal calcites by meteoric waters under variable water/rock ratios. The13C contents and87Sr/86Sr ratios of these younger, low temperature calcites appear to be partially buffered by the isotopic composition of the original hydrothermal calcite.Pyrite is often associated with the fracture calcites. These pyrites display a wide range in δ34S values of about 70%., which suggests that sulphide precipitation occurred under semi-closed conditions. These data indicate that fracture permeability has been a major control on the isotopic composition of fracture minerals since formation of the gneiss. 相似文献
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Karima Haddou Amina Bendaoud Nouria Belaidi Amina Taleb 《Environmental Earth Sciences》2018,77(13):520
Very few studies have evaluated the role of the hyporheic zone (HZ) in aquatic ecosystem functioning or the factors driving hyporheic exchange flows on a large scale, especially in a semi-arid environment such as the Tafna watershed in Algeria. To understand this role through time and space, hydrogeochemical parameters, particularly nitrate concentrations (NO3–N), were measured monthly between February 2013 and April 2014 in surface water (SW), interstitial water (IW) and groundwater (GW) along a 170-km stretch from the river’s source to the outlet into the main stream of the Tafna River and its Isser and Chouly tributaries. The significant longitudinal evolution of NO3–N in the HZ was related to stream order and distance from the source. Moreover, the study indicated a significant difference between nitrate concentrations in the riffles (R) and pools (P) of the Tafna wadi. Principal component analysis (PCA) revealed the considerable impact of agriculture on nitrate concentrations. This study indicated on a large scale that nitrate-rich HZ contributed to increasing surface nitrate concentrations in upwelling sites and could be an important nitrate source for downstream SW, particularly during low-water (LW) periods when the Tafna can run dry on the surface. Thus, these results underline the importance of hyporheic zones functioning to the water quality of the watershed (process of enrichment and retention of nitrogen). 相似文献
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Fluid-assisted zircon and monazite growth within a shear zone: a case study from Finnmark,Arctic Norway 总被引:1,自引:0,他引:1
Christopher L. Kirkland Martin J. Whitehouse Trond Slagstad 《Contributions to Mineralogy and Petrology》2009,158(5):637-657
The U–Pb ages, REE content, and oxygen isotopic composition of zircon rims developed within a major shear zone in the Kalak
Nappe Complex (KNC), Arctic Norway have been determined along with the age of monazite crystals. Different generations of
granitic veins have been distinguished based on both field criteria and monazite ages of 446 ± 3 and 424 ± 3 Ma. Within each
of these veins, inherited zircon cores are mantled by homogeneous low CL-response zircon rims which yield a range of concordant
U–Pb dates of ca. 470–360 Ma. Significant numbers of zircon rims coincide with the timing of monazite crystallization. The
zircon rims have moderate light REE enrichment compared to cores, distinctive (Sm/La)
n
values of less than 12, and La between 0.3 and 10 ppm. This indicates free elemental exchange between newly formed zircon
rims and the surrounding matrix. The rims have calculated accumulated alpha-radiation dosages corresponding with a crystalline
structure and δ18O values of 1‰. This implies rim crystallization directly from a zirconium-saturated hydrothermal fluid which was modified
by some silicate melt. Growth of the zircon rims was prolonged and locally variable due to preferential fluid flow. A third
type of zircon can be recognized, forming both rims and cores, with high alpha-radiation doses, and significant enrichment
in La, Pr, and Eu. These are interpreted as low-temperature hydrothermally altered metamict zircons. The high volatile input
and partial melting in the shear zone favoured prolonged zircon rim growth due to its ability to easily nucleate on inherited
seeds. On the other hand, monazite, susceptible to dissolution and re-growth, crystallized in brief episodes, as has been
predicted from theoretical phase diagrams. From a regional perspective, these results elucidate cryptic Ar–Ar cooling ages,
providing the first record of a Late Ordovician heating and cooling phase within the KNC prior to the climactic Scandian collision. 相似文献
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A lumped-parameter model of groundwater balance is proposed that permits an estimate of discharge variability in comparison
with the variability of recharge, by taking into account the influence of aquifer parameters. Recharge–discharge relationships
are analysed with the model for cases of deterministic and stochastic recharge time-series variations. The model is applied
to study the temporal variability of groundwater discharge in a river valley in the territory of Tajikistan, an independent
republic in Central Asia.
Received, April 1996 Revised, August 1997 Accepted, March 1998 相似文献