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1.
《Applied Geochemistry》2006,21(2):253-268
The Dalaman and Köyceğiz thermal springs are from karstic limestones belonging to Upper Cretaceous to Burdigalian Beydağları autochthon and Carboniferous to Lutetian Lycian nappes. They have measured temperatures of 24– 41 °C, specific electrical conductivities of 14,310–45,600 μS/cm, and are dominated by Na (1550–8500 mg/kg) and Cl (2725–15,320 mg/kg). The heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults. Meteoric waters and seawaters recharge the reservoir rocks, are heated at depth with increasing geothermal gradient, and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs. While thermal waters move up to the surface, they mix with different proportions of seawater and cold fresh waters. The seawater contribution to the thermal waters varies from 24% to 78%. Lake waters in the area are connected with thermal waters. Consequently, their chemical composition is influenced by the chemistry of thermal waters. Chemical equilibrium modelling based on measured outlet temperatures and measured pH shows that all the waters are oversaturated with respect to quartz and K-mica and undersaturated with respect to Al(OH)3, anorthite, gypsum, siderite and SiO2(a). Albite, alunite, aragonite, Ca-montmorillonite, calcite, chalcedony, chlorite, dolomite, Fe(OH)3(a), fluorite, gypsum, illite, K-feldspar, kaolinite and sepiolite minerals are mostly oversaturated or undersaturated. Mineral saturation studies of the thermal springs indicate that dolomite, chalcedony and quartz are most likely to cause scaling at outlet conditions. Assessments from various chemical geothermometers, and Na–K–Mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65–90 °C. The temperatures obtained from quartz, quartz-steam loss, Mg/Li geothermometers and mineral equilibrium diagrams give the most reasonable results. 相似文献
2.
《Applied Geochemistry》2006,21(11):1969-1985
Gossan Creek, a headwater stream in the SE Upsalquitch River watershed in New Brunswick, Canada, contains elevated concentrations of total Hg (HgT up to 60 μg/L). Aqueous geochemical investigations of the shallow groundwater at the headwaters of the creek confirm that the source of Hg is a contaminated groundwater plume (neutral pH with Hg and Cl concentrations up to 150 μg/L and 20 mg/L, respectively), originating from the Murray Brook mine tailings, that discharges at the headwaters of the creek. The discharge area of the contaminant plume was partially delineated based on elevated pH and Cl concentrations in the groundwater. The local groundwater outside of the plume contains much lower concentrations of Hg and Cl (<0.1 μg/L and 3.8 mg/L, respectively) and displays the chemical characteristics of an acid-sulfate weathering system, with low pH (4.1–5.5) and elevated concentrations of Cu, Zn, Pb and SO4 (up to 5400 μg Cu/L, 8700 μg Zn/L, 70 μg Pb/L and 330 mg SO4/L), derived from oxidation of sulfide minerals in the Murray Brook volcanogenic massive sulfide deposit and surrounding bedrock. The HgT mass loads measured at various hydrologic control points along the stream system indicate that 95–99% of the dissolved HgT is attenuated in the first 3–4 km from the source. Analyses of creek bed sediments for Au, Ag, Cu, Zn, Pb and Hg indicate that these metals have partitioned strongly to the sediments. Mineralogical investigations of the contaminated sediments using analytical scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), reveal discrete particles (<1–2 μm) of metacinnabar (HgS), mixed Au–Ag–Hg amalgam, Cu sulfide and Ag sulfide. 相似文献
3.
New isotopic and chemical data on the sodium bicarbonate water and associated gases from the Razdolnoe Spa located in the coastal zone of Primorsky Kray of the Russian Far East, together with previous stable isotope data (δ18O, δD, δ13C), allow elucidation of the origin and evolution of the groundwater and gases from the spa. The water is characterized by low temperature (12 °C), TDS – 2.5–6.0 g/L, high contents of B (∼5 mg/L) and F (4.5 mg/L) and low contents of Cl and SO4. Water isotopic composition indicates its essentially meteoric origin which may comply with an older groundwater that was recharged under different (colder) climatic conditions. Major components of bubbling gases are CH4 (68 vol%), N2 (28%) and CO2 (4%). The obtained values δ13C and δD for CO2 and CH4 definitely indicate the marine microbial origin of methane. Thus the high methane content in the waters relates to the biochemical processes and presence of a dispersed organic matter in the host rocks. Based on the regional hydrogeology and the geological structure of the Razdolnoe Spa, Mesozoic fractured rocks containing Na–HCO3 mineral water and gases are reservoir rocks, a chemical composition of water and gases originates in different environmental conditions. 相似文献
4.
Streams and rivers are major exporters of C and other dissolved materials from watersheds to coastal waters. In streams and rivers, substantial amounts of terrigenous organic C is metabolized and degassed as CO2 to the atmosphere. A long-term evaluation of CO2 dynamics in streams is essential for understanding factors controlling CO2 dynamics in streams in response to changes in climate and land-use. Long-term changes in the partial pressure of CO2 (pCO2) were computed in the Anacostia River and the lower Potomac River in the Chesapeake Bay watershed. Long-term estimates were made using routine monitoring data of pH, total alkalinity, and dissolved nutrients from 1985 to 2006 at 14 stations. Longitudinal variability in pCO2 dynamics was also investigated along these rivers downstream of the urban Washington D.C. metropolitan area. Both rivers were supersaturated with CO2 with respect to atmospheric CO2 levels (392 μatm) and the highly urbanized Anacostia waters (202–9694 μatm) were more supersaturated than the Potomac waters (557–3800 μatm). Long-term variability in pCO2 values may be due to changes in river metabolism and organic matter and nutrient loadings. Both rivers exchange significant amounts of CO2 with the atmosphere (i.e., Anacostia at 0.2–72 mmol m−2 d−1 and Potomac at 0.12–24 mmol m−2 d−1), implying that waterways receiving organic matter and nutrient subsidies from urbanized landscapes have the potential to increase river metabolism and atmospheric CO2 fluxes along the freshwater–estuarine continuum. 相似文献
5.
The dissolution kinetics of carbonate rocks sampled from the Keg River Formation in Northeast British Columbia were measured at 50 bar pCO2 and 105 °C, in both natural and synthetic brines of 0.4 M ionic strength. Natural brines yielded reaction rates of −12.16 ± 0.11 mol cm−2 s−1 for Log RCa, and −12.64 ± 0.05 for Log RMg. Synthetic brine yielded faster rates of reaction than natural brines. Experiments performed on synthetic brines, spiked with 10 mmol of either Sr or Zn, suggest that enhanced reaction rates observed in synthetic brines are due to a lack of trace ion interaction with mineral surfaces. Results were interpreted within the surface complexation model framework, allowing for the discrimination of reactive surface sites, most importantly the hydration of the >MgOH surface site. Dissolution rates extrapolated from experiments predict that CO2 injected into the Keg River Formation will dissolve a very minor portion of rock in contact with affected formation waters. 相似文献
6.
《Applied Geochemistry》2005,20(10):1831-1847
The groundwater contribution into Green Lake and Black Lake (Vescovo Lakes Group), two cover collapse sinkholes in Pontina Plain (Central Italy), was estimated using water chemistry and a 222Rn budget. These data can constrain the interactions between sinkholes and deep seated fluid circulation, with a special focus on the possibility of the bedrock karst aquifer feeding the lake. The Rn budget accounted for all quantifiable surface and subsurface input and output fluxes including the flux across the sediment–water interface. The total value of groundwater discharge into Green Lake and Black Lake (∼540 ± 160 L s−1) obtained from the Rn budget is lower than, but comparable with historical data on the springs group discharge estimated in the same period of the year (800 ± 90 L s−1). Besides being an indirect test for the reliability of the Rn-budget “tool”, it confirms that both Green and Black Lake are effectively springs and not simply “water filled” sinkholes. New data on the water chemistry and the groundwater fluxes into the sinkhole area of Vescovo Lakes allows the assessment of the mechanism responsible for sinkhole formation in Pontina Plain and suggests the necessity of monitoring the changes of physical and chemical parameters of groundwater below the plain in order to mitigate the associated risk. 相似文献
7.
Natural gas reservoirs in organic-rich shales in the Appalachian and Michigan basins in the United States are currently being produced via hydraulic fracturing. Stratigraphically-equivalent shales occur in the Canadian portion of the basins in southwestern Ontario with anecdotal evidence of gas shows, yet there has been no commercial shale gas production to date. To provide baseline data in the case of future environmental issues related to hydraulic fracturing and shale gas production, such as leakage of natural gas, saline water, and/or hydraulic fracturing fluids, and to evaluate hydrogeochemical controls on natural gas accumulations in shallow groundwater in general, this study investigates the origin and distribution of natural gas and brine in shallow aquifers across southwestern Ontario. An extensive geochemical database of major ion and trace metal chemistry and methane concentrations of 1010 groundwater samples from shallow, domestic wells in bedrock and overburden aquifers throughout southwestern Ontario was utilized. In addition, select wells (n = 36) were resampled for detailed dissolved gas composition, δ13C of CH4, C2, C3, and CO2, and δD of CH4. Dissolved gases in groundwater from bedrock and overburden wells were composed primarily of CH4 (29.7–98.6 mol% of total gas volume), N2 (0.8–66.2 mol%), Ar + O2 (0.2–3.4 mol%), and CO2 (0–1.2 mol%). Ethane was detected, but only in low concentrations (<0.041 mol%), and no other higher chain hydrocarbons were present, except for one well in overburden overlying the Dundee Formation, which contained 0.81 mol% ethane and 0.21 mol% propane. The highest methane concentrations (30 to >100 in situ % saturation) were found in bedrock wells completed in the Upper Devonian Kettle Point Formation, Middle Devonian Hamilton Group and Dundee Formation, and in surficial aquifers overlying these organic-rich shale-bearing formations, indicating that bedrock geology is the primary control on methane occurrences. A few (n = 40) samples showed Na–Cl–Br evidence of brine mixing with dilute groundwater, however only one of these samples contained high (>60 in situ % saturation) CH4. The relatively low δ13C values of CH4 (−89.9‰ to −57.3‰), covariance of δD values of CH4 and H2O, positive correlation between δ13C values of CH4 and CO2, and lack of higher chain hydrocarbons (C3+) in all but one dissolved gas sample indicates that the methane in groundwater throughout the study area is primarily microbial in origin. The presence or absence of alternative electron acceptors (e.g. dissolved oxygen, Fe, NO3, SO4), in addition to organic substrates, controls the occurrence of microbial CH4 in shallow aquifers. Microbial methane has likely been accumulating in the study area, since at least the Late Pleistocene to the present, as indicated by the co-variance and range of δD values of CH4 (−314‰ to −263‰) and associated groundwater (−19‰ to −6‰ δD-H2O). 相似文献
8.
《Applied Geochemistry》2006,21(12):2188-2200
Phosphate-induced metal stabilization involving the reactive medium Apatite II™ [Ca10−xNax(PO4)6−x(CO3)x(OH)2], where x < 1, was used in a subsurface permeable reactive barrier (PRB) to treat acid mine drainage in a shallow alluvial groundwater containing elevated concentrations of Zn, Pb, Cd, Cu, SO4 and NO3. The groundwater is treated in situ before it enters the East Fork of Ninemile Creek, a tributary to the Coeur d’Alene River, Idaho. Microbially mediated SO4 reduction and the subsequent precipitation of sphalerite [ZnS] is the primary mechanism occurring for immobilization of Zn and Cd. Precipitation of pyromorphite [Pb10(PO4)6(OH,Cl)2] is the most likely mechanism for immobilization of Pb. Precipitation is occurring directly on the original Apatite II. The emplaced PRB has been operating successfully since January of 2001, and has reduced the concentrations of Cd and Pb to below detection (2 μg L−1), has reduced Zn to near background in this region (about 100 μg L−1), and has reduced SO4 by between 100 and 200 mg L−1 and NO3 to below detection (50 μg L−1). The PRB, filled with 90 tonnes of Apatite II, has removed about 4550 kg of Zn, 91 kg of Pb and 45 kg of Cd, but 90% of the immobilization is occurring in the first 20% of the barrier, wherein the reactive media now contain up to 25 wt% Zn. Field observations indicate that about 30% of the Apatite II material is spent (consumed). 相似文献
9.
Sixteen bottled waters of various Sicilian brands, 11 natural mineral waters and five normal drinking waters, were analyzed for major and trace inorganic components by ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The bottled waters represent a variety of water types with significantly different compositions in terms of salinity, major components and trace elements. Chemically, they range from Ca–HCO3 and Ca–SO4 to Na–HCO3 types. Total dissolved solids ranges from 54 to 433 mg/L, total hardness from 25 to 238 mg/L CaCO3, and measured Na content from 5.7 to 57 mg/L. According to total dissolved ions, all the bottled waters were classified as oligomineral (50 < TDS < 500 mg/L). All the bottled waters analyzed here had elemental concentrations which did not exceed the guideline and directive values, although a high concentration of Al was noted for one bottled water (O7, central Sicily) and high Rb and V in a bottled water (O1) from the Etna volcanic area. With regard to trace elements, the chemical quality of bottled waters was assessed by a metal index (MI). Chemical characteristics were compared with 10 tap water samples from private houses or public places, representative of the public water supply in Palermo, the largest and most densely populated city in Sicily. The municipal waters analyzed, belonging to HCO3-alkaline earth and Cl–SO4-alkaline earth waters, showed concentrations of chemical inorganic components well within drinking water limits. The data also indicated that the water supplied by the municipal authority is of fair quality, although fairly hard and high in Na concentration. Several considerations indicate that there is no sufficient reason to prefer bottled waters to tap waters. 相似文献
10.
《Applied Geochemistry》2006,21(8):1288-1300
Phosphate-induced metal stabilization involving the reactive medium Apatite II™ [Ca10−xNax(PO4)6−x(CO3)x(OH)2], where x < 1, was used in a subsurface permeable reactive barrier (PRB) to treat acid mine drainage in a shallow alluvial groundwater containing elevated concentrations of Zn, Pb, Cd, Cu, SO4 and NO3. The groundwater is treated in situ before it enters the East Fork of Ninemile Creek, a tributary to the Coeur d’Alene River, Idaho. Microbially mediated SO4 reduction and the subsequent precipitation of sphalerite [ZnS] is the primary mechanism occurring for immobilization of Zn and Cd. Precipitation of pyromorphite [Pb10(PO4)6(OH,Cl)2] is the most likely mechanism for immobilization of Pb. Precipitation is occurring directly on the original Apatite II. The emplaced PRB has been operating successfully since January of 2001, and has reduced the concentrations of Cd and Pb to below detection (2 μg L−1), has reduced Zn to near background in this region (about 100 μg L−1), and has reduced SO4 by between 100 and 200 mg L−1 and NO3 to below detection (50 μg L−1). The PRB, filled with 90 tonnes of Apatite II, has removed about 4550 kg of Zn, 91 kg of Pb and 45 kg of Cd, but 90% of the immobilization is occurring in the first 20% of the barrier, wherein the reactive media now contain up to 25 wt% Zn. Field observations indicate that about 30% of the Apatite II material is spent (consumed). 相似文献
11.
The linkage between the iron and the carbon cycles is of paramount importance to understand and quantify the effect of increased CO2 concentrations in natural waters on the mobility of iron and associated trace elements. In this context, we have quantified the thermodynamic stability of mixed Fe(III) hydroxo-carbonate complexes and their effect on the solubility of Fe(III) oxihydroxides. We present the results of carefully performed solubility measurements of 2-line ferrihydrite in the slightly acidic to neutral–alkaline pH ranges (3.8–8.7) under constant pCO2 varying between (0.982–98.154 kPa) at 25 °C.The outcome of the work indicates the predominance of two Fe(III) hydroxo carbonate complexes FeOHCO3 and Fe(CO3)33−, with formation constants log*β°1,1,1 = 10.76 ± 0.38 and log β°1,0,3 = 24.24 ± 0.42, respectively.The solubility constant for the ferrihydrite used in this study was determined in acid conditions (pH: 1.8–3.2) in the absence of CO2 and at T = (25 ± 1) °C, as log*Ks,0 = 1.19 ± 0.41.The relative stability of the Fe(III)-carbonate complexes in alkaline pH conditions has implications for the solubility of Fe(III) in CO2-rich environments and the subsequent mobilisation of associated trace metals that will be explored in subsequent papers. 相似文献
12.
The Diyadin Geothermal area, located in the eastern part of Anatolia (Turkey) where there has been recent volcanic activity, is favorable for the formation of geothermal systems. Indeed, the Diyadin geothermal system is located in an active geodynamic zone, where strike-slip faults and tensional cracks have developed due to N–S regional compression. The area is characterized by closely spaced thermal and mineralized springs, with temperatures in the range 30–64 °C, and flowrates 0.5–10 L/s. Thermal spring waters are mainly of Ca(Na)-HCO3 and Ca(Mg)-SO4 types, with high salinity, while cold groundwater is mostly of Ca(Na, Mg)-HCO3 type, with lower salinity. High contents of some minor elements in thermal waters, such as F, B, Li, Rb, Sr and Cs probably derive from enhanced water–rock interaction.Thermal water samples collected from Diyadin are far from chemical equilibrium as the waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters. The temperatures of the deep geothermal reservoirs are estimated to be between 92 and 156 °C in Diyadin field, based on quartz geothermometry, while slightly lower estimates are obtained using chalcedony geothermometers. The isotopic composition of thermal water (δ18O, δ2H, δ3H) indicates their deep-circulating meteoric origin. The waters are likely to have originated from the percolation of rainwater along fractures and faults to the deep hot reservoir. Subsequent heating by conduction due to the presence of an intrusive cupola associated with the Tendurek volcano, is followed by the ascent of deep waters to the surface along faults and fractures that act as hydrothermal conduits.Modeling of the geothermal fluids indicates that the fluid is oversaturated with calcite, aragonite and dolomite, which matches travertine precipitation in the discharge area. Likewise, the fluid is oversaturated with respect to quartz, and chalcedony indicating the possibility of siliceous precipitation near the discharge areas. A conceptual hydro-geochemical model of the Diyadin thermal waters based on the isotope and chemical analytical results, has been constructed. 相似文献
13.
Measurements of low-level concentrations of halogenated volatile organic compounds (VOCs) and estimates of groundwater age interpreted from 3H/3He and SF6 data have led to an improved understanding of groundwater flow, water sources, and transit times in a karstic, fractured, carbonate-rock aquifer at the Leetown Science Center (LSC), West Virginia. The sum of the concentrations of a set of 16 predominant halogenated VOCs (TDVOC) determined by gas chromatography with electron-capture detector (GC–ECD) exceeded that possible for air–water equilibrium in 34 of the 47 samples (median TDVOC of 24,800 pg kg−1), indicating that nearly all the water sampled in the vicinity of the LSC has been affected by addition of halogenated VOCs from non-atmospheric source(s). Leakage from a landfill that was closed and sealed nearly 20 a prior to sampling was recognized and traced to areas east of the LSC using low-level detection of tetrachloroethene (PCE), methyl chloride (MeCl), methyl chloroform (MC), dichlorodifluoromethane (CFC-12), and cis-1,2-dichloroethene (cis-1,2-DCE). Chloroform (CHLF) was the predominant VOC in water from domestic wells surrounding the LSC, and was elevated in groundwater in and near the Fish Health Laboratory at the LSC, where a leak of chlorinated water occurred prior to 2006. The low-level concentrations of halogenated VOCs did not exceed human or aquatic-life health criteria, and were useful in providing an awareness of the intrinsic susceptibility of the fractured karstic groundwater system at the LSC to non-atmospheric anthropogenic inputs. The 3H/3He groundwater ages of spring discharge from the carbonate rocks showed transient behavior, with ages averaging about 2 a in 2004 following a wet climatic period (2003–2004), and ages in the range of 4–7 a in periods of more average precipitation (2008–2009). The SF6 and CFC-12 data indicate older water (model ages of 10s of years or more) in the low-permeability shale of the Martinsburg Formation located to the west of the LSC. A two-a record of specific conductance, water temperature, and discharge recorded at 30-min intervals demonstrated an approximately 3-month lag in discharge at Gray Spring. The low groundwater ages of waters from the carbonate rocks support rapid advective transport of contaminants from the LSC vicinity, yet the nearly ubiquitous occurrence of low-level concentrations of halogenated VOCs at the LSC suggests the presence of long-term persistent sources, such as seepage from the closed and sealed landfill, infiltration of VOCs that may persist locally in the epikarst, exchange with low-permeability zones in fractured rock, and upward leakage of older water that may contain elevated concentrations of halogenated VOCs from earlier land use activities. 相似文献
14.
Chemical weathering of Mg, Ca-silicates and alumino-silicates contributes significantly to the drawdown of atmospheric CO2 over long time scales. The present work focuses on how this mode of weathering may change in the presence of free-living bacteria in oligotrophic waters, which compose most of the surface freshwaters of the Earth. Forsterite (Fo90) was reacted for 1 week with a stable Escherichia coli population in water maintained at 37 °C and neutral pH in a batch reactor. Control samples with suspensions of pure olivine powders and E. coli cells in pure water were also used for reference. Olivine controls reproduce the Mg, Si and Fe release in solutions predicted from rates published in the literature with pH shifts of less than 0.5 unit. After 1 week, under abiotic conditions, weathered surfaces are enriched in Fe and Fe3+ relative to the initial composition of the mineral. Bacterial controls (without minerals) show decreasing Eh with increasing cell concentrations (−50 mV with 7 × 107 cells/mL and −160 mV with 8 × 108 cells/mL). Magnesium concentrations in bacterial control solutions are in the μg/L range and can be accounted for by the release of Mg from dead cells. More than 80% of the cells were still alive after 1 week. The solutions obtained in the experiments in which olivine reacts in the presence of cells show Mg and Si concentrations a few tens of percent lower than in the mineral control samples, with a prominent depletion of Fe(III) content of the mineral surfaces. Magnesium mass balance discounts both significant bacterial uptake and inhibition of the Mg dissolution rates as a consequence of changing pH and Eh. Coating by bacterial cell layers is also negligible. E. coli reduces the chemical weathering of olivine. This study infers that the presence of free-living Proteobacteria, a prevalent group of subsurface bacteria, should decrease the amount of riverine Mg released by chemical weathering of mafic rocks. 相似文献
15.
《Applied Geochemistry》2005,20(8):1496-1517
Chloride concentrations were as high as 230 mg/L in water from the surface discharge of long-screened production wells in Pleasant Valley, Calif., about 100 km NW of Los Angeles. Wells with the higher Cl− concentrations were near faults that bound the valley. Depending on well construction, high-Cl−water from different sources may enter a well at different depths. For example, Cl− concentration in the upper part of some wells completed in overlying aquifers influenced by irrigation return were as high as 220 mg/L, and Cl− concentrations in water sampled within wells at depths greater than 450 m were as high as 500 mg/L. These high-Cl− waters mix within the well during pumping and produce the water sampled at the surface discharge. Changes in the major ion, minor ion, trace element, and δ34S and δ13C isotopic composition of water in wells with depth were consistent with changes resulting from SO4 reduction, precipitation of calcite, and cation exchange. The chemical and isotopic composition of high-Cl− water from deep wells trends towards the composition of oil-field production water from the study area. Chloride concentrations in oil-field production water present at depths 150 m beneath freshwater aquifers were 2200 mg/L, and Cl− concentrations in underlying marine rock were as high as 4400 mg/L. High-Cl− concentrations in water from deeper parts of wells were associated with dissolved organic C composed primarily of hydrophobic neutral compounds believed to be similar to those associated with petroleum in underlying deposits. These compounds would not be apparent using traditional sampling techniques and would not be detected using analytical methods intended to measure contamination. 相似文献
16.
《Applied Geochemistry》2006,21(4):580-613
To quantify and explain the contributions by pollution and chemical weathering to their composition, we studied the chemistries of springs and surface waters in the mountainous part of the Vouga River basin. Water samples were collected during a number of consecutive summer campaigns. Recharge rates were derived from monitored discharge rates within the basin. Very large contributions by meteoric, agricultural and domestic sources to the water chemistries were found, identified by the chloride, sulfate and nitrate concentrations: on average only 1/4 to 1/3 of the solutes could be attributed to chemical weathering. Two petrologic units characterize the river basin: granites and metasediments. The waters collected within metasediment units are distinct from those in granite terrain by a higher magnesium concentration. On that basis, it could be estimated that the Rio Vouga, when leaving the mountainous part of the basin, has for some 2/5 a signature determined by chemical weathering in the metasediments. The dominant primary minerals subject to chemical weathering are plagioclase (Pl) and biotite (in granite) or Pl and chlorite (in metasediment). Kaolinite, gibbsite and vermiculite are the major weathering products where annual precipitation (P) > 1000 mm y−1, and kaolinite, vermiculite and smectite where P was lower. Using an algorithm based on the ratio of dissolved silica to bicarbonate, the contributions of chemical weathering of primary minerals could be unraveled. The results show that in granite the export rate (as mol ha−1 y−1 wt%mineral−1) of oligoclase (Pl with An10–30) was 5.0 ± 2.6 and of biotite 3.2 ± 2.6, while in metasediment these rates for albite (Pl with An0–10) are 16.5 ± 8.9 and for chlorite are 0.5 ± 0.5. The observed decrease of dissolved silica in surface waters relative to springs was ascribed to (summer) uptake by aquatic biota. 相似文献
17.
Pristine diorite drill cores, obtained from the Äspö Hard Rock Laboratory (HRL, Sweden), were used to study the retention properties of fresh, anoxic crystalline rock material towards the redox-sensitive uranium. Batch sorption experiments and spectroscopic methods were applied for this study. The impact of various parameters, such as solid-to-liquid ratio (2–200 g/L), grain size (0.063–0.2 mm, 0.5–1 mm, 1–2 mm), temperature (room temperature and 10 °C), contact time (5–108 days), initial U(VI) concentration (3 × 10−9 to 6 × 10−5 M), and background electrolyte (synthetic Äspö groundwater and 0.1 M NaClO4) on the U(VI) sorption onto anoxic diorite was studied under anoxic conditions (N2). Comparatively, U(VI) sorption onto oxidized diorite material was studied under ambient atmosphere (pCO2 = 10−3.5 atm). Conventional distribution coefficients, Kd, and surface area normalized distribution coefficients, Ka, were determined. The Kd value for the U(VI) sorption onto anoxic diorite in synthetic Äspö groundwater under anoxic conditions by investigating the sorption isotherm amounts to 3.8 ± 0.6 L/kg which corresponds to Ka = 0.0030 ± 0.0005 cm (grain size 1–2 mm). This indicates a weak U sorption onto diorite which can be attributed to the occurrence of the neutral complex Ca2UO2(CO3)3(aq) in solution. This complex was verified as predominating U species in synthetic Äspö groundwater by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Compared to U sorption at room temperature under anoxic conditions, U sorption is further reduced at decreased temperature (10 °C) and under ambient atmosphere. The U species in aqueous solution as well as sorbed on diorite were studied by in situ time-resolved attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. A predominant sorbing species containing a UO2(CO3)34− moiety was identified. The extent of U sorption onto diorite was found to depend more on the low sorption affinity of the Ca2UO2(CO3)3(aq) complex than on reduction processes of uranium. 相似文献
18.
《Chemie der Erde / Geochemistry》2016,76(1):63-75
Geothermal resources are very rich in Yunnan, China. However, source of dissolved solutes in geothermal water and chemical evolution processes remain unclear. Geochemical and isotopic studies on geothermal springs and river waters were conducted in different petrological-tectonic units of western Yunnan, China. Geothermal waters contain Ca–HCO3, Na–HCO3, and Na (Ca)–SO4 type, and demonstrate strong rock-related trace elemental distributions. Enhanced water–rock interaction increases the concentration of major and trace elements of geothermal waters. The chemical compositions of geothermal waters in the Rehai geothermal field are very complicated and different because of the magma chamber developed at the shallow depth in this area. In this geothermal field, neutral-alkaline geothermal waters with high Cl, B, Li, Rb Cs, As, Sb, and Tl contents and acid–sulfate waters with high Al, Mn, Fe, and Pb contents are both controlled by magma degassing and water–rock interaction. Geothermal waters from metamorphic, granite, and sedimentary regions (except in the Rehai area) exhibit varying B contents ranging from 3.31 mg/L to 4.49 mg/L, 0.23 mg/L to 1.24 mg/L, and <0.07 mg/L, respectively, and their corresponding δ11B values range from −4.95‰ to −9.45‰, −2.57‰ to −8.85‰, and −4.02‰ to +0.06‰. The B contents of these geothermal waters are mainly controlled by leaching host rocks in the reservoir, and their δ11B values usually decrease and achieve further equilibrium with its surrounding rocks, which can also be proven by the positive δ18O-shift. In addition to fluid–rock reactions, the geothermal waters from Rehai hot springs exhibit higher δ11B values (−3.43‰ to +1.54‰) than those yielded from other areas because mixing with the magmatic fluids from the shallow magma. The highest δ11B of steam–heated waters (pH 3.25) from the Zhenzhu spring in Rehai is caused by the fractionation induced by pH and the phase separation of coexisting steam and fluids. Given the strong water–rock interaction, some geothermal springs in western Yunnan show reservoir temperatures higher than 180 °C, which demonstrate potential for electricity generation and direct-use applications. The most potential geothermal field in western Yunnan is located in the Rehai area because of the heat transfer from the shallow magma chamber. 相似文献
19.
《Applied Geochemistry》2006,21(9):1522-1538
Factors controlling the chemical composition of water interacting with finely-crushed kimberlite have been investigated by sampling pore waters from processed kimberlite fines stored in a containment facility. Discharge water from the diamond recovery plant and surface water from the containment facility, which acts as plant intake water, were also sampled. All waters sampled are pH-neutral, enriched in SO4, Mg, Ca, and K, and low in Fe. Pore-water samples, representing the most concentrated waters, are characterized by the highest SO4 (up to 4080 mg l−1), Mg (up to 870 mg l−1), and Ca (up to 473 mg l−1). The water discharged from the processing plant has higher concentrations of all major dissolved constituents than the intake water. The dominant minerals present in the processed fines and the kimberlite ore are serpentine and olivine, with small amounts of Ca sulphate and Fe sulphide restricted to mud xenoclasts. Reaction and inverse modeling suggest that much of the water-rock interaction takes place within the plant and involves the dissolution of chrysotile and Ca sulphate, and precipitation of silica and Mg carbonate. Evapoconcentration also appears to be a significant process affecting pore water composition in the containment facility. The reaction proposed to be occurring during ore processing involves the dissolution of CO2(g) and may represent an opportunity to sequester atmospheric CO2 through mineral carbonation. 相似文献
20.
Recent studies have documented the expulsion of methane and oil to the Albian paleoseabed in the Basque-Cantabrian Basin. They interpret that hydrocarbon generation and expulsion were triggered by seismically recorded magmatic intrusions which metamorphosed organic-rich host sediments. An outcrop within the basin was selected to investigate organic matter evolution and sediment degassing due to an igneous body. This intrusion is a 5 m thick Late Albian basaltic sill that intruded mudstones of the Black Flysch Group, near Gorliz (north Iberia). Vitrinite and bitumen reflectance profiles and metamorphic mineral distribution in the overburden indicate that the sill produced a thermal effect that increases toward the intrusion, defining a 2 m thick (minimum) contact aureole.Geochemical profiles of TOC, S1, S2, HI and PC show a gradual decrease toward the sill indicating organic carbon loss and increase in the thermal maturity of the organic matter in the same direction. Concordantly, gas chromatograms show a loss of n-alkanes and a predominance of the shorter chain length homologues adjacent to the sill. Tmax and PI (S1/S1 + S2) values increase toward the sill which suggests an increase in the thermal stress and in the extent of kerogen pyrolysis, respectively.Organic carbon loss in the aureole was the result of carbon devolatilization and formation of CO2 and CH4 gases. The newly formed CO2 reacted with pore waters to precipitate 13C depleted carbonate minerals in the aureole and in sill fractures. CH4 escaped from the aureole via hydrofractures to the paleoseabed, where methane-derived authigenic carbonates were formed. 相似文献