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1.
Hydrogeochemical processes controlling surface water chemistry were examined in five small (<1.5 km 2) forested catchments that have contrasting bedrock lithologies of granite, and conglomerate, and are distributed in the southeast of Seto district, central Japan. Watersheds developed on these two bedrocks differ in their ability to neutralize atmospheric acid (pH ~4.5) deposition. The study was conducted to (1) characterize the hydrogeochemical processes controlling surface water chemistry, and (2) to elucidate acidification of spring and stream waters using data from three sampling campaigns conducted from August to October 2000. Stream and spring water solutes fall into two general groups according to concentration: alkaline, relatively high pH (5.2–7.7) and high cation concentrations (HCO 3 -, Cl -, base cations), and dilute, low pH (4.2–5.5) waters. Concentrations of trace metals (Al, Ba, Sr) showed a strong negative correlation with pH, suggesting the mobility of these metals in the dissolved load of catchments underlain by Tokai conglomerate. The strontium isotope ratio ( 87Sr/ 86Sr) of rock and soil, plant, precipitation, and surface water samples was used to identify different reservoirs within the ecosystem. Low Si concentrations in stream and spring waters from the conglomerate area, with a relatively high pool of SiO 2, >90 (wt%), suggest slow chemical weathering. The dissolved solute concentrations are generally of similar magnitude in stream waters within the catchments of similar bedrock lithology. The high inverse correlation ( r 2=0.72) between pH and SO 4 – concentrations and the high positive correlation ( r 2 =0.90) between Ba and SO 4 – concentrations in waters draining Tokai conglomerate suggest that barite (BaSO 4) is being dissolved in an acidic environment. The three catchments were identified as being sensitive to acidic deposition because the bedrock conglomerate provided little capacity to buffer acidic inputs. The soils from the granite area have a high cation-exchange capacity (CEC an average of 868 µmol/kg), and are nearly ten times greater than the soils from the conglomerate area. Because ion exchange, besides weathering, is the main source that counteracts soil acidification, the sensitivity to further acidification may increase. 相似文献
2.
Sitangshu Chatterjee Arnab Sarkar A. S. Deodhar B. P. Biswal A. Jaryal H. V. Mohokar U. K. Sinha Ashutosh Dash 《Environmental Earth Sciences》2017,76(2):97
Thermal waters at the Godavari valley geothermal field are located in the Khammam district of the Telangana state, India. The study area consists of several thermal water manifestations having temperature in the range 36–76 °C scattered over an area of ~35 km2. The thermal waters are Na–HCO3 type with moderate silica and TDS concentrations. In the present study, detailed geochemical (major and trace elements) and isotope hydrological investigations are carried out to understand the hydrogeochemical evolution of these thermal waters. Correlation analysis and principal component analysis (PCA) are performed to classify the thermal waters and to identify the different geochemical processes controlling the thermal water geochemistry. From correlation matrix, it is seen that TDS and EC of the thermal springs are mainly controlled by HCO3 and Na ions. In PCA, thermal waters are grouped into two distinct clusters. One cluster represents thermal waters from deeper aquifer and other one from shallow aquifer. Lithium and boron concentrations are found to be similar followed by rubidium and caesium concentrations. Different ternary plots reveal rock–water interaction to be the dominant mechanism for controlling trace element concentrations. Stable isotopes (δ18O, δ2H) data indicate the meteoric origin of the thermal waters with no appreciable oxygen-18 shift. The low tritium values of the samples originating from deeper aquifer reveal the long residence time (>50 years) of the recharging waters. XRD results of the drill core samples show that quartz constitutes the major mineral phase, whereas kaolinite, dolomite, microcline, calcite, mica, etc. are present as minor constituents. Quartz geothermometer suggests a reservoir temperature of 100 ± 20 °C which is in good agreement with the values obtained from K–Mg and Mg-corrected K–Mg–Ca geothermometers. 相似文献
3.
Antonio Cardona Carlos Gutierrez-Ojeda Manuel Martínez-Morales Gerardo Ortiz-Flores Luis González-Hita 《Environmental Earth Sciences》2018,77(23):785
The Cuatrociénegas area is useful for the investigation of the effect of groundwater extraction in the Chihuahuan freshwater xeric ecoregion. It has been investigated at this time using a selection of geochemical indicators (major, minor and trace elements) and δ34S data, to characterize the origin of groundwater, the main geochemical processes and the mineral/groundwater interactions controlling the baseline geochemistry. The area is composed of limestones of Mesozoic age, with a composite thickness of about 500 m, overlaid by basin fill (poorly consolidated young sediments). Substantial water extraction and modification of natural discharges from the area along the last century have produced a detrimental impact on ecosystem structure and function. Water–rock interactions, mixing and evaporative processes dominate the baseline groundwater quality. Natural recharge is HCO3–Ca type in equilibrium with calcite, low salinity (TDS?<?500 mg/L), Cl? lower than 11 mg/L and average Li+ concentration of 0.005 mg/L. Along the groundwater flow systems, δ34S evidence and mass transfer calculations indicate that Cretaceous gypsum dissolution and dedolomitization reactions adjust water composition to the SO4–Ca type. The increase of water–rock interaction is reflected by Cl? values increase (average 68 mg/L), TDS up to about 1500 mg/L and an average Li+ concentration of 0.063 mg/L. Calculations with chemical geothermometers indicate that temperature at depth could be at maximum of 15–20 °C higher than field-measured temperature for pozas. After groundwater is discharged to the surface, chemical evolution continues; water evaporation, CO2 degassing and precipitation of minerals such as gypsum, calcite and kaolinite represent the final processes and reactions controlling water chemical composition. 相似文献
4.
《Applied Geochemistry》1999,14(2):237-254
Two major types of groundwater can be readily distinguished in the Variscian crystalline basement of the Black Forest in S–W Germany. Saline thermal water utilized in spas has its origin in 3–4 km deep reservoirs and developed its composition by 3 component mixing of surface freshwater, saltwater (of ultimately marine origin) and a water–rock reaction component. In contrast to the thermal water, CO2-rich mineral water, tapped and bottled from many wells in the Black Forest, has low salinities but a TDS distribution similar to that of thermal water. It developed its chemical composition entirely by reaction of CO2-rich water with the gneissic or granitic aquifer rock matrix. Particularly important is the contribution of various plagioclase dissolution and weathering reactions that may, at some locations, involve precipitation and dissolution of secondary calcite. Sodium/Ca ratios of water and of rock forming plagioclase in the basement rocks suggests that plagioclase weathering is strongly incongruent. Calcium is released to the water, whereas Na remains fixed to the albite feldspar component.The major element composition of 192 water samples used in this study also indicates a clear vertical stratification of the type of water chemistry; Ca–HCO3 near the surface, Na–Ca–HCO3–SO4 at intermediate depth and Na–Ca–Cl at great depth.The mean permeability of Black Forest granite is about K=10−6 m/s; it is significantly lower in gneisses (gneiss: mean K=5×10−8 m/s) leading to focused flow through granite. Highly permeable fracture and fault zones, particularly in granite, are utilized by high-TDS saline deep groundwater as ascent channels and flow paths. Although spatially closely associated, the topography driven upwelling system of saline deep water and the near-surface flow system of CO2-rich mineral waters are hydraulically and chemically unconnected. 相似文献
5.
N. A. Kharitonova G. A. Chelnokov V. V. Kulakov N. N. Zykin 《Russian Journal of Pacific Geology》2008,2(6):535-544
This work reports new hydrochemical data on the two types of cold high p CO2 groundwaters from the Mukhen deposit (Khabarovsk district). The first type is classed with HCO3-Ca-Mg waters with a relatively low TDS (up to 1.7 g/l) and high concentrations of Fe2+, Mn2+, Ba2+, and SiO2. The second type is of HCO3-Na composition with high TDS (up to 14 g/l) and elevated Li+, B, Sr2+, Br?, and I?. New oxygen (δ18O) and hydrogen (δD) isotopic data on the waters and carbon (δ13C) isotopic data on the gas phase, together with a detailed geological and hydrogeological analysis of the study area, allowed us to decipher the origin of both the mineral waters. Based on the tritium content (3H) in the ground and surface waters of the area, the duration of the mineral water circulation was estimated. It was established that the both types of groundwaters were formed during interaction of meteoric water with bedrock under active influence of CO2, however HCO3-Na groundwaters have longer residence time than HCO3-Ca-Mg groundwaters. 相似文献
6.
We present a weathering mass balance of the presently glaciated Rhône and Oberaar catchments, located within the crystalline Aar massif (central Switzerland). Annual chemical and physical weathering fluxes are calculated from the monthly weighted means of meltwater samples taken from July, 1999 to May, 2001 and are corrected for precipitation inputs. The meltwater composition issuing from the Oberaar and Rhône catchments is dominated by calcium, which represents 81% and 55% of the total cation flux respectively (i.e. 555 and 82-96 keq km−2 yr−1). The six to seven times higher Ca2+ denudation flux from the Oberaar catchment is attributed to the presence of a strongly foliated gneissic zone. The gneissic zone has an elevated calcite content (as reflected by the 4.6 times higher calcite content of the suspended sediments from Oberaar compared to Rhône) and a higher mechanical erosion rate (resulting in a higher flux of suspended sediment). The mean flux of suspended calcite of the Oberaar meltwaters during the ablation period is 7 times greater than that of the Rhône meltwaters. Taking the suspended calcite as a proxy for the total (including sub-glacial sediments) weathering calcite surface area, it appears that the available surface area is an important factor in controlling weathering rates. However, we also observe an increased supply of protons for carbonate dissolution in the Oberaar catchment, where the sulphate denudation flux is six times greater. Carbonic acid is the second important source of protons, and we calculate that three times as much atmospheric CO2 is drawn down (short term) in the Oberaar catchment. Silica fluxes from the two catchments are comparable with each other, but are 100 kmol km2 yr−1 lower than fluxes from physically comparable, non-glaciated basins. 相似文献
7.
Sitangshu Chatterjee Uday Kumar Sinha Archana. S. Deodhar Md. Arzoo Ansari Nathu Singh Ajay Kumar Srivastava R. K. Aggarwal Ashutosh Dash 《Environmental Earth Sciences》2017,76(18):638
Uttarakhand geothermal area, located in the central belt of the Himalayan geothermal province, is one of the important high temperature geothermal fields in India. In this study, the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir. The thermal waters are mainly Ca–Mg–HCO3 type with moderate silica and TDS concentrations. Mineral saturation states calculated from PHREEQC geochemical code indicate that thermal waters are supersaturated with respect to calcite, dolomite, aragonite, chalcedony, quartz (SI > 0), and undersaturated with respect to gypsum, anhydrite, and amorphous silica (SI < 0). XRD study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters. Stable isotopes (δ18O, δ2H) data confirm the meteoric origin of the thermal waters with no oxygen-18 shift. The mixing phenomenon between thermal water with shallow ground water is substantiated using tritium (3H) and chemical data. The extent of dilution is quantified using tritium content of thermal springs and non-thermal waters. Classical geothermometers, mixing model, and multicomponent fluid geothermometry modeling (GeoT) have been applied to estimate the subsurface reservoir temperature. Among different classical geothermometers, only quartz geothermometer provide somewhat reliable estimation (96–140 °C) of the reservoir temperature. GeoT modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite, quartz, chalcedony, brucite, tridymite, cristobalite, talc, at the temperature 130 ± 5 °C which is in good agreement with the result obtained from the mixing model. 相似文献
8.
S.L. Shvartsev N.A. Kharitonova O.E. Lepokurova G.A. Chelnokov 《Russian Geology and Geophysics》2017,58(1):37-46
We present the chemical and isotope compositions of the water and gas phases of the unique Mukhen cold high-pCO2 spa. Estimated 518O, 5D, and 513Ctic values and data on geology and hydrogeology of the studied area indicate that the source of the groundwaters is meteoric waters, whereas carbon dioxide is of deep genesis and numerous regional faults are gas-feeding channels. Calculations of equilibrium reactions in the water-rock system show that the upper-aquifer waters (HCO3-Ca-Mg) with low TDS are undersaturated with carbonate minerals, montmorillonites, and aluminosilicates but are oversaturated with kaolinite, whereas the lower-aquifer waters (HCO3-Na) with high TDS are oversaturated with calcite, dolomite, and clay minerals but are undersaturated with main aluminosilicates. We propose a new concept of the formation of these groundwaters, demonstrating that long interaction between rocks and groundwaters in the presence of CO2 and considerable precipitation of secondary minerals are responsible for the high TDS of the lower-aquifer waters (up to 14 g/L) and their geochemical type (HCO3-Na) and unusual isotope composition (518O = -25.2%c, 5D = -69.0%c). 相似文献
9.
M.I. Leybourne R.N. Betcher W.D. McRitchie C.A. Kaszycki D.R. Boyle 《Chemical Geology》2009,260(3-4):221-233
New major, trace and isotopic geochemical results from a regional study of springs discharging from the major carbonate rock aquifer in the Interlake Region of Manitoba, Canada, are used to understand water–rock reactions, timing of recharge/discharge, tufa formation processes, and as baseline data. Spring waters are fresh with total dissolved solids (TDS) concentrations ranging from 150 to 880 mg/L. Waters discharging in the northern part of the study area have lower TDS, are dominantly Ca–Mg–HCO3 waters with low SO4 concentrations (<< 50 mg/L), and appear to have interacted primarily with Silurian carbonate lithologies. In contrast, waters in the southeastern part of the study area have higher TDS and have elevated SO4 concentrations (up to 210 mg/L). Spring waters have elevated Mg/Camolar (1.23 ± 0.23), typically greater than congruent dissolution of dolomite. Ca and Mg concentrations and Mg/Camolar indicate that groundwater residence times were sufficient to allow equilibration with bedrock dolomite lithologies; elevated tritium in northern waters indicates a significant recharge component in the 1960's and 1970's. Tufa precipitates that have formed from many of the spring waters are low-Mg calcite (MgO = 1.70 to 5.80 wt.%). Sr concentrations are variable (57 to 657 ppm) and tufa Sr/Camolar ratios appear to be entirely controlled by spring water Sr/Camolar. Empirically determined Sr distribution coefficients (DSr = 0.389 ± 0.083) indicate rapid crystallization following CO2 degassing, consistent with heavier δ13CVPDB compared to spring waters. Sulfate concentrations are generally too low for calcitization (dedolomitization) reactions driven by anhydrite dissolution to be the dominant control on the elevated groundwater Mg/Camolar, implying either extensive sulfate reduction along the flow paths (however, δ13CDIC suggests the elevated SO4 is more consistent with Fe-sulfide oxidation), or that other processes are involved. Major ion ratios suggest that the waters in the southern part of the study area are more consistent with interaction with siliciclastic rocks than with anhydrite dissolution. We suggest that calcitization (dedolomitization) reactions driven by anhydrite dissolution may not dominate all carbonate aquifers and that mixing of waters in karst conduits combined with ion exchange reactions are important controls on water chemistry in these systems. 相似文献
10.
Relative contributions of silicate and carbonate rocks to riverine Sr fluxes in the headwaters of the Ganges 总被引:1,自引:0,他引:1
Mike J. Bickle Hazel J. Chapman Nigel B.W. Harris Talat Ahmad 《Geochimica et cosmochimica acta》2005,69(9):2221-2240
Exhumation of the Himalayan-Tibetan orogen is implicated in the marked rise in seawater 87Sr/86Sr ratios since 40 Ma. However both silicate and carbonate rocks in the Himalaya have elevated 87Sr/86Sr ratios and there is disagreement as to how much of the 87Sr flux is derived from silicate weathering. Most previous studies have used element ratios from bedrock to constrain the proportions of silicate- and carbonate-derived Sr in river waters. Here we use arrays of water compositions sampled from the head waters of the Ganges in the Indian and Nepalese Himalaya to constrain the end-member element ratios. The compositions of tributaries draining catchments restricted to a limited range of geological units can be described by two-component mixing of silicate and carbonate-derived components and lie on a plane in multicomponent composition space. Key elemental ratios of the carbonate and silicate components are determined by the intersection of the tributary mixing plane with the planes Na = 0 for carbonate and constant Ca/Na for silicate. The fractions of Sr derived from silicate and carbonate sources are then calculated by mass-balance in Sr-Ca-Mg-Na composition space. Comparison of end-member compositions with bedrock implies that secondary calcite deposition may be important in some catchments and that dissolution of low-Mg trace calcite in silicate rocks may explain discrepancies in Sr-Ca-Na-Mg covariation. Alternatively, composition-dependent precipitation or incongruent dissolution reactions may rotate mixing trends on cation-ratio diagrams. However the calculations are not sensitive to transformations of the compositions by incongruent dissolution or precipitation processes provided that the transformed silicate and carbonate component vectors are constrained. Silicates are calculated to provide ∼50% of the dissolved Sr flux from the head waters of the Ganges assuming that discrepancies between Ca-Mg-Na covariation and the silicate rock compositions arise from addition of trace calcite. If the Ca-Mg-Na mixing plane is rotated by composition-dependent secondary calcite deposition, this estimate would be increased. Moreover, when 87Sr/86Sr ratios of the Sr inputs are considered, silicate Sr is responsible for 70 ± 16% (1σ) of the 87Sr flux forcing changes in seawater Sr-isotopic composition. Since earlier studies predict that silicate weathering generates as little as 20% of the total Sr flux in Himalayan river systems, this study demonstrates that the significance of silicate weathering can be greatly underestimated if the processes that decouple the water cation ratios from those of the source rocks are not properly evaluated. 相似文献
11.
A hydrochemical study of the Hammam Righa geothermal waters in north-central Algeria 总被引:1,自引:0,他引:1
Mohamed Belhai Yasuhiro Fujimitsu Fatima Zohra Bouchareb-Haouchine Abdelhamid Haouchine Jun Nishijima 《中国地球化学学报》2016,35(3):271-287
This study focuses on the hydrochemical characteristics of 47 water samples collected from thermal and cold springs that emerge from the Hammam Righa geothermal field, located in north-central Algeria. The aquifer that feeds these springs is mainly situated in the deeply fractured Jurassic limestone and dolomite of the Zaccar Mount. Measured discharge temperatures of the cold waters range from 16.0 to 26.5 °C and the hot waters from 32.1 to 68.2 °C. All waters exhibited a near-neutral pH of 6.0–7.6. The thermal waters had a high total dissolved solids (TDS) content of up to 2527 mg/l, while the TDS for cold waters was 659.0–852.0 mg/l. Chemical analyses suggest that two main types of water exist: hot waters in the upflow area of the Ca–Na–SO4 type (Hammam Righa) and cold waters in the recharge zone of the Ca–Na–HCO3 type (Zaccar Mount). Reservoir temperatures were estimated using silica geothermometers and fluid/mineral equilibria at 78, 92, and 95 °C for HR4, HR2, and HR1, respectively. Stable isotopic analyses of the δ18O and δD composition of the waters suggest that the thermal waters of Hammam Righa are of meteoric origin. We conclude that meteoric recharge infiltrates through the fractured dolomitic limestones of the Zaccar Mount and is conductively heated at a depth of 2.1–2.2 km. The hot waters then interact at depth with Triassic evaporites located in the hydrothermal conduit (fault), giving rise to the Ca–Na–SO4 water type. As they ascend to the surface, the thermal waters mix with shallower Mg-rich groundwater, resulting in waters that plot in the immature water field in the Na–K–Mg diagram. The mixing trend between cold groundwaters from the recharge zone area (Zaccar Mount) and hot waters in the upflow area (Hammam Righa) is apparent via a chloride-enthalpy diagram that shows a mixing ratio of 22.6 < R < 29.2 %. We summarize these results with a geothermal conceptual model of the Hammam Righa geothermal field. 相似文献
12.
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
13.
259 stream water and 21 bulk precipitation samples have been studied between April 2008 and December 2010 in order to assess baseline hydrochemical conditions in a rural area of NW Spain. Stream waters are related to five nested catchments (<10 km2) with apparent low mean residence times. Their hydrochemical characteristics are closely related to bulk precipitation although clear evidences of seasonal (flushing, dilution, sediment desorption, etc.), lithological (schist vs. granite substrate) and anthropogenic (land use, contamination) effects are also described. 相似文献
14.
Babita Neogi Abhay Kumar Singh D. D. Pathak Aaditya Chaturvedi 《Environmental Earth Sciences》2017,76(14):489
Mine water samples collected from different mines of the North Karanpura coalfields were analysed for pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), major anions, cations and trace metals to evaluate mine water geochemistry and assess solute acquisition processes, dissolved fluxes and its suitability for domestic, industrial and irrigation uses. Mine water samples are mildly acidic to alkaline in nature. The TDS ranged from 185 to 1343 mg L?1 with an average of 601 mg L?1. Ca2+ and Mg2+ are the dominant cations, while SO4 2? and HCO3 ? are the dominant anions. A high concentration of SO4 2? and a low HCO3 ?/(HCO3 ? + SO4 2?) ratio (<0.50) in the majority of the water samples suggest that either sulphide oxidation or reactions involving both carbonic acid weathering and sulphide oxidation control solute acquisition processes. The mine water is undersaturated with respect to gypsum, halite, anhydrite, fluorite, aluminium hydroxide, alunite, amorphous silica and oversaturated with respect to goethite, ferrihydrite, quartz. About 40% of the mine water samples are oversaturated with respect to calcite, dolomite and jarosite. The water quality assessment shows that the coal mine water is not suitable for direct use for drinking and domestic purposes and needs treatment before such utilization. TDS, TH, F?, SO4 2?, Fe, Mn, Ni and Al are identified as the major objectionable parameters in these waters for drinking. The coal mine water is of good to suitable category for irrigation use. The mines of North Karanpura coalfield annually discharge 22.35 × 106 m3 of water and 18.50 × 103 tonnes of solute loads into nearby waterways. 相似文献
15.
Water–granite interaction: Clues from strontium,neodymium and rare earth elements in soil and waters
《Applied Geochemistry》2006,21(8):1432-1454
Strontium-, Nd-, and rare-earth-element-isotope data are presented from rock, weathered rock (arene) and saprolite, sediment and soil, shallow and deep groundwater (e.g. mineral-water springs), and surface waters in the Margeride massif, located in the French Massif Central. Granitoid rock and gneiss are the main lithologies encountered in the Margeride, which corresponds to a large and 5-km-deep laccolith. Compared to bedrock, the Sr isotopes in arene, regolith, sediment and soil strongly diverge with a linear increase in the 87Sr/86Sr and Rb/Sr ratios. Neodymium isotopes fluctuate least between bedrock and the weathering products. In order to characterise the theoretical Sr isotopic signature IRf(Sr) of water interacting with granite, a dissolution model was applied, based on the hypothesis that most of the Sr comes from the dissolution of plagioclase, K-feldspar and biotite. Similar to the Sr model, an approach was developed for modelling the theoretical Nd isotopic signature IRf(Nd) of water interacting with a granite, assuming that most Nd originates from dissolution of the same minerals as those that yield Sr, plus apatite. The IRf(Sr) ratio of water after equilibration with the Sr derived from minerals was calculated for the Margeride granite and compared to values measured in surface- and groundwaters. Comparison of the results shows agreement between the calculated IRf(Sr) and the observed 87Sr/86Sr ratios. When calculating the IRf(Nd) ratio of water after equilibration with the Nd derived from minerals of the Margeride granite, the results indicated good agreement with surface-water values, whereas mineralised waters analysed within the Margeride hydrosystem could not be directly linked to weathering of the granite alone. Because the recharge area of deep groundwater is located on the Margeride massif, very deep circulation involving interaction with other rocks (e.g. shales) at depths of >5 km must be considered. 相似文献
16.
H. Ferchichi M. F. Ben Hamouda B. Farhat A. Ben Mammou 《International Journal of Environmental Science and Technology》2018,15(11):2473-2492
The integration of the statistical approaches and GIS tools with the hydrogeological and geological contexts allowed the assessment of the processes that cause groundwater quality deterioration in the great important deltaic aquifer in the northeastern Tunisia (Medjerda Lower Valley Aquifer). The spatial variation of the groundwater parameters and the molar ratio (Cl?/Br?) were also used to determine the possible impacts from seawater intrusion and from the septic tank leachate. Sixty shallow groundwater samples were collected in 2014 and analyzed for major and trace ions over an area of about 1090 km2 to determine the suitability for drinking or agricultural purposes. The total dissolved solids (TDS) content ranges from 1005 to 19,254 mgl?1 with a mean value of 3477.18 mgl?1. The chemistry is dominated by the sodium–chloride waters (55%). Mapping of TDS, Cl?, Na+, SO42? and NO3? using kriging method shows a clear increase in salinity toward the coastline accompanied by Na+ and Cl? increase which may be related to seawater intrusion and halite dissolution. Locally, higher nitrate concentration is related to the agricultural activities inducing contribution of chemical fertilizers and irrigation with treated wastewater. The saturation indices indicate that all carbonate minerals tend to reach saturation equilibrium confirming water–rock interactions, while evaporitic minerals are still in sub-saturation state and may increase the salinity of the groundwater. The principal component analysis proves the occurrence of groundwater contamination principally by seawater intrusion in the factor I (74.15%) and secondary by an anthropogenic source in the factor II (10.35%). 相似文献
17.
CS Suma K Srinivasamoorthy K Saravanan S Gopinath R Prakash A Faizal Khan 《Arabian Journal of Geosciences》2016,9(18):703
An attempt has been made in Chinnar sub basin of Dharmapuri district, South India to isolate the geochemistry of uranium occurrences in groundwater. The geology of the area is mainly of charnockite and granite gneiss. Groundwater samples were collected for two different seasons post and pre monsoon in two different litho units (granite gneiss and charnockite) and analysed for major, minor and uranium concentrations. Higher uranium (18.45 μg L?1) has been recorded during pre monsoon season in granite gneiss with increasing pH. The saturation index calculation for the groundwater isolated minerals like uaraninite, coffinite, haiweeite and soddyite to be precipitating and uranium oxides like UO2.25, UO2.25beta, UO2.33beta as oversaturated. The Eh-pH diagram attempted represents solubility of uraninite within the pH range of 6.0 to 8.0. The study isolate uranium in groundwater of the study area is controlled by the presence of (U4O9) uranium oxide. 相似文献
18.
The chemical composition of water sampled in a 700 m deep underground barite-fluorite mine in the crystalline basement of the Black Forest area (SW Germany) varies systematically with depth and the length of flow paths trough, the fracture porosity of the gneiss matrix. Calcium and sulfate increase as a result of a combined sulfide oxidation and plagioclase alteration reaction. The gneiss contains andesine–plagioclase (An20–An40) and is rich in primary sulfide. As an effect of Ca and SO4 release by the prime water–rock reaction, dissolved oxygen decreases and the waters become more reduced. The waters have Cl/Br mass ratios of about 50, which is very close to that of experimentally leached gneiss powders indicating that the rock matrix is the source of the halogens. The waters are undersaturated with respect to calcite in the upper parts of the mine. With increasing reaction progress, calcite saturation is reached and carbonate forms as a reaction product of the prime reaction that also controls the partial pressure of CO2 to progressively lower values. The chemical evolution of groundwater in fractured basement of the Clara mine suggests that the partial pressure of CO2 is an internally buffered parameter rather than a controlling external variable. 相似文献
19.
Reconciling the elemental and Sr isotope composition of Himalayan weathering fluxes: insights from the carbonate geochemistry of stream waters 总被引:3,自引:0,他引:3
Determining the relative proportions of silicate vs. carbonate weathering in the Himalaya is important for understanding atmospheric CO2 consumption rates and the temporal evolution of seawater Sr. However, recent studies have shown that major element mass-balance equations attribute less CO2 consumption to silicate weathering than methods utilizing Ca/Sr and 87Sr/86Sr mixing equations. To investigate this problem, we compiled literature data providing elemental and 87Sr/86Sr analyses for stream waters and bedrock from tributary watersheds throughout the Himalaya Mountains. In addition, carbonate system parameters (PCO2, mineral saturation states) were evaluated for a selected suite of stream waters. The apparent discrepancy between the dominant weathering source of dissolved major elements vs. Sr can be reconciled in terms of carbonate mineral equilibria. Himalayan streams are predominantly Ca2+-Mg2+-HCO3− waters derived from calcite and dolomite dissolution, and mass-balance calculations demonstrate that carbonate weathering contributes ∼87% and ∼76% of the dissolved Ca2+ and Sr2+, respectively. However, calculated Ca/Sr ratios for the carbonate weathering flux are much lower than values observed in carbonate bedrock, suggesting that these divalent cations do not behave conservatively during stream mixing over large temperature and PCO2 gradients in the Himalaya.The state of calcite and dolomite saturation was evaluated across these gradients, and the data show that upon descending through the Himalaya, ∼50% of the streams evaluated become highly supersaturated with respect to calcite as waters warm and degas CO2. Stream water Ca/Mg and Ca/Sr ratios decrease as the degree of supersaturation with respect to calcite increases, and Mg2+, Ca2+, and HCO3− mass balances support interpretations of preferential Ca2+ removal by calcite precipitation. On the basis of patterns of saturation state and PCO2 changes, calcite precipitation was estimated to remove up to ∼70% of the Ca2+ originally derived from carbonate weathering. Accounting for the nonconservative behavior of Ca2+ during riverine transport brings the Ca/Sr and 87Sr/86Sr composition of the carbonate weathering flux into agreement with the composition of carbonate bedrock, thereby permitting consistency between elemental and Sr isotope approaches to partitioning stream water solute sources. These results resolve the dissolved Sr2+ budget and suggest that the conventional application of two-component Ca/Sr and 87Sr/86Sr mixing equations has overestimated silicate-derived Sr2+ and HCO3− fluxes from the Himalaya. In addition, these findings demonstrate that integrating stream water carbonate mineral equilibria, divalent cation compositional trends, and Sr isotope inventories provides a powerful approach for examining weathering fluxes. 相似文献
20.
The relative contributions of dolomite to calcite weathering related to riverine fluxes are investigated on a highly resolved spatial scale in the diverse watersheds of Slovenia, which previous work has shown have some of the highest carbonate-weathering intensities in the world and suggests that dolomite weathering is favored over limestone weathering in mixed carbonate watersheds. The forested Sava and So?a River watersheds of Slovenia with their headwaters in the Julian Alps drain alpine regions with thin soils (<30 cm) and dinaric karst regions with thicker soils (0 to greater than 70 cm) all developed over bedded Mesozoic carbonates (limestone and dolomite), and siliclastic sediments is the ideal location for examining temperate zone carbonate weathering. This study extends previous work, presenting geochemical data on source springs and documenting downstream geochemical fluctuations within tributaries of the Sava and So?a Rivers. More refined sampling strategies of springs and discrete drainages permit directly linking the stream Mg2+/Ca2+ ratios to the local bedrock lithology and the HCO3 ? concentrations to the relative soil depths of the tributary drainages. Due to differences in carbonate source lithologies of springs and tributary streams, calcite and dolomite weathering end members can be identified. The Mg2+/Ca2+ ratio of the main channel of the Sava River indicates that the HCO3 ? concentration can be attributed to nearly equal proportions by mass of dolomite relative to calcite mineral weathering (e.g., Mg2+/Ca2+ mole ratio of 0.33). The HCO3 ? concentration and pCO2 values increase as soil thickness and alluvium increase for discrete spring samples, which are near equilibrium with respect to calcite. Typically, this results in approximately 1.5 meq/l increase in HCO3 ? from the alpine to the dinaric karst regions. Streams in general do not change in HCO3 ?, Mg2+/Ca2+, or Mg2+/HCO3 ? concentrations down course, but warming and degassing of CO2 produce high degrees of supersaturation with respect to calcite. Carbonate-weathering intensity (mmol/km2-s) is highest within the alpine regions where stream discharge values range widely to extreme values during spring snowmelt. Overall, the elemental fluxes of HCO3 ?, Ca2+, and Mg2+ from the tributary watersheds are proportional to the total water flux because carbonates dissolve rapidly to near equilibrium. Importantly, dolomite weathers preferentially over calcite except for pure limestone catchments. 相似文献