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1
Takahashi, H. A., T. Nakamura, H. Tsukamoto, K. Kazahaya, H. Handa, and A. Hirota. "Radiocarbon Dating of Groundwater in Granite Fractures in Abukuma Province, Northeast Japan." Radiocarbon 55, no. 2 (2013): 894–904. http://dx.doi.org/10.1017/s0033822200058057.
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Knowledge of the groundwater age is indispensable for understanding groundwater flow in crystalline rocks. The present study is the first to discuss the radiocarbon ages of groundwater in Abukuma granite, Fukushima Prefecture, northeast Japan. The vertical profiles of 14C dates and δ13C are obtained from 3 boreholes (depths of 140, 230, and 306 m). Chemical and carbon isotopic compositions suggest that dead-carbon contamination of groundwater occurred during groundwater storage in the fractures. 14C concentration was corrected by using isotopic mass balance in which dead-carbon contamination of the groundwater was considered. The 14C dates ranged from modern to ≃16 ka. The relationship between tritium and 14C data in 1 borehole suggests the simultaneous inflow of shallow groundwater to deeper levels occur for the depths between 60 and 100 m. The vertical profiles of 14C dates indicate a relatively constant age of 10–16 ka for groundwater deeper than 100 m, which may have been influenced by rapid sea-level changes after the glacial period.
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Engel, R., DJ Mcfarlane, and G. Street. "The influence of dolerite dykes on saline seeps in southwestern Australia." Soil Research 25, no. 2 (1987): 125. http://dx.doi.org/10.1071/sr9870125.
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Geophysical surveys, soil and geological mapping and hydrologic studies have been used to show an association between dolerite dykes and the occurrence of saline seeps on two catchments in southwestern Australia. The role of the dykes in the location of the saline seeps is explained and the potential contribution of routine geophysical surveys to salinity studies is highlighted. Magnetic surveys and soil and geological mapping identified dolerite dykes crossing the main drainage line of each catchment. Soil resistivity and conductivity surveys showed that these dykes are associated with saline soils. Seismic refraction surveys over these dykes indicate deeper weathering profiles. Groundwater pressures and hydraulic conductivities measured in bores across one of the weathered dykes showed that the clay saprolite formed above the dolerite is less permeable than the surrounding weathered granite. The lower permeability is probably due to the finer texture of the saprolite and/or a lower frequency of preferred flow pathways. The clay formed above the dolerite acts as a linear hydraulic barrier to lateral groundwater flow and results in the discharge of saline groundwaters into surface soils.
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Rouleau, A., and J. E. Gale. "Stochastic discrete fracture simulation of groundwater flow into an underground excavation in granite." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 24, no. 2 (1987): 99–112. http://dx.doi.org/10.1016/0148-9062(87)91929-2.
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Akanbi, Olanrewaju Akinfemiwa, and Moshood ‘Niyi Tijani. "Sustainability and Conceptual Groundwater Hydraulic Models of Basement Aquifers." Materials and Geoenvironment 66, no. 2 (2019): 87–98. http://dx.doi.org/10.2478/rmzmag-2019-0016.
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AbstractGroundwater flow of the basement terrains of the Ibarapa region was studied by carrying out pumping test and measurement of borehole inventory. The view was to identify the associated aquifer systems from the time-drawdown curves, quantify the estimable hydraulic properties and develop hypothetical models for the understanding of the groundwater flow in the area underlain by diverse crystalline bedrocks. Three aquifer types were identified namely, dual, leaky and regolith. The yield of groundwater in dual and leaky aquifers that dominated terrains underlain by amphibolite and gneisses was sustainable, but the discharge of regolith aquifers mainly associated with migmatite and granite terrains declined at late pumping stage. The transmissivities of the dual and leaky aquifers were between 2.02 and 11.65 m2/day, while those of regolith aquifers were mostly less than 1.00 m2/day. The average aquifer transmissivities in m2/day by bedrocks were: 6.85, 2.57, 0.76 and 1.72, correspondingly. The inter-relationships between transmissivities and groundwater discharge showed diverse aquifer representations, from sustainable high-yielding to unsustainable low-yielding types. Conscientious effort is, therefore, required for well construction in the area.
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MIYAKITA, Jun-ichi, and Katsuhiro FUJISAKI. "Groundwater Flow Modeling in the Granite Region. A Case Study in the Kibi Plateau, Okayama Prefecture." Journal of the Japan Society of Engineering Geology 33, no. 1 (1992): 7–16. http://dx.doi.org/10.5110/jjseg.33.7.
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Skoulikidis, Nikolaos T., Anastasia Lampou, and Sofia Laschou. "Unraveling Aquatic Quality Controls of a Nearly Undisturbed Mediterranean Island (Samothraki, Greece)." Water 12, no. 2 (2020): 473. http://dx.doi.org/10.3390/w12020473.
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Due to its rough, mountainous relief, Samothraki remains one of the last minimally disturbed islands in the Mediterranean. This paper examines the hydrogeochemical regime of the island’s surface waters as it results from geological, morphological, and hydro(geo)logical controls within a frame of minimally disturbed environmental conditions. Shallow, fractured groundwater aquifers, in combination with steep slopes and predominant weathering resistant rocks, bring about flashy stream regimes with remarkably low solute concentrations. Streams and springs revealed hydrochemical similarities. Contrary to streams chiefly draining sedimentary rocks, streams underlined by granite and ophiolite rocks do not respond hydrochemically to geochemical differences. Using ion proportions instead of concentrations, geochemical fingertips of magmatic stream basins were detected. Atmospheric inputs largely affect stream and spring composition, e.g., by 75% regarding sodium. Only 20% of dissolved oxygen and pH variance was assigned to biological activity, while nutrient levels were consistent with the undisturbed conditions of the island, except nitrate. Small mountainous springs and brooks fed by restricted, fractured groundwater aquifers with perennial flow, despite scarce summer rainfalls, may be fueled by cloud and fog condensation. High night-day stream flow differences, high atmospheric humidity predominately occurring during the night, and low stream water travel times point out toward this phenomenon.
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Ofterdinger, U. S., Ph Renard, and S. Loew. "Hydraulic subsurface measurements and hydrodynamic modelling as indicators for groundwater flow systems in the Rotondo granite, Central Alps (Switzerland)." Hydrological Processes 28, no. 2 (2012): 255–78. http://dx.doi.org/10.1002/hyp.9568.
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Ji, Sung-Hoon, Byeong-Hak Park, and Kyung-Woo Park. "Distortion of the Estimated Hydraulic Conductivity from a Hydraulic Test in Fractured Rock Due to Excessive Injection or Extraction." Water 12, no. 10 (2020): 2712. http://dx.doi.org/10.3390/w12102712.
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In this study, we discussed distortion of the estimated hydraulic conductivity from a hydraulic test due to excessive injection or extraction of groundwater by evaluating the influence of nonlinear flow. Pulse, slug, and constant head withdrawal tests with various head displacements were conducted in fractured granite rock, and the changes of representative Reynolds numbers (Re) during the tests were calculated. The Forchheimer equation and cubic law were used to evaluate the influence of nonlinear flow on the hydraulic tests, and thus the possibility of distortion of the estimated hydraulic conductivity. Our results showed that there was little possibility that nonlinear flow occurred during the pulse tests in the test zones. In the slug tests at several test zones, however, the estimated hydraulic conductivities were likely to be distorted due to nonlinear flow. Except for the test zones with low permeability, the scale effects of the estimated hydraulic conductivities from different types of tests were observed. These results indicated that the scale effect and distortion of the hydraulic parameters can be evaluated by conducting various types of hydraulic tests.
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Drake, Henrik, Ellen Kooijman, and Melanie Kielman-Schmitt. "Using 87Sr/86Sr LA-MC-ICP-MS Transects within Modern and Ancient Calcite Crystals to Determine Fluid Flow Events in Deep Granite Fractures." Geosciences 10, no. 9 (2020): 345. http://dx.doi.org/10.3390/geosciences10090345.
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The strontium isotope signature (87Sr/86Sr) of calcite precipitated in rock fractures and faults is a frequently used tool to trace paleofluid flow. However, bedrock fracture networks, such as in Precambrian cratons, have often undergone multiple fracture reactivations resulting in complex sequences of fracture mineral infillings. This includes numerous discrete calcite crystal overgrowths. Conventional 87Sr/86Sr analysis of dissolved bulk samples of such crystals is not feasible as they will result in mixed signatures of several growth zonations. In addition, the zonations are too fine-grained for sub-sampling using micro-drilling. Here, we apply high spatial resolution 87Sr/86Sr spot analysis (80 µm) in transects through zoned calcite crystals in deep Paleoproterozoic granitoid fractures using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to trace discrete signs of paleofluid flow events. We compare the outermost calcite growth zone with 87Sr/86Sr values of the present-day groundwater sampled in the same boreholes to distinguish potential modern precipitates. We then connect our results to previously reported radiometric dating and C and O isotope signatures to understand the temporal history and physicochemical evolution of fluid flow within the fractures. Comparisons of modern calcite precipitated in a borehole over a period of 17 years with modern waters prove the concept of using 87Sr/86Sr as a marker for fluid origin in this environment and for how 87Sr/86Sr changed during marine water infiltration. Intermittent calcite precipitation over very long time spans is indicated in calcite of the currently open fractures, showing an evolution of 87Sr/86Sr from ~0.705–0.707—a population dated to ~1.43 billion years—to crystal overgrowth values at ~0.715–0.717 that overlap with the present-day groundwater values. This shows that high spatial resolution Sr isotope analysis of fine-scaled growth zonation within single calcite crystals is applicable for tracing episodic fluid flow in fracture networks.
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Piggott, Andrew R., and Derek Elsworth. "Characterization of fracture aperture by inverse analysis." Canadian Geotechnical Journal 30, no. 4 (1993): 637–46. http://dx.doi.org/10.1139/t93-055.
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Formulation and application of a procedure for characterizing the spatial distribution of aperture within a single fracture in rock are discussed. A simultaneous-inversion approach is used to construct the aperture distribution that best replicates the variability apparent in measured hydraulic and electrical data. In this approach, aperture distributions are generated from a specified model, flow is simulated for each of multiple test types and configurations, the error of approximating the measured data with the simulated results is evaluated, and an optimization algorithm is used to minimize the error with respect to parameters regulating the aperture distribution. The procedure is applied to data obtained from laboratory tests conducted on a natural fracture in granite. Three aperture distributions with similar macroscopic characteristics are inferred from the data. Corroboration of these distributions is obtained from the simulation of tracer transport within the fracture and comparison of the simulated results with measured data. Key words : characterization, fractured rock, groundwater flow, contaminant transport, inverse analysis.
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Rahman, Nazrin, Edy Tonnizam Mohamad, and Rosli Saad. "Groundwater Potential Assessment Using 2-D Resistivity Method In Kluang, Johor (Malaysia)." Warta Geologi 46, no. 3 (2020): 220–24. http://dx.doi.org/10.7186/wg463202009.
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Sources of clean water are decreasing due to rapid usage, contaminated surface waters, pollution and dry season. The dependence on the existing water source is not enough to fulfil the increasing demand of population in Malaysia. In order to overcome the problem, groundwater source is the most suitable alternative. 2-D resistivity method was carried out in a granitic area of Kluang, Johor to delineate and locate groundwater resource. 5 survey lines were conducted by using ABEM SAS4000 terrameter and electrode selector which were connected to 41 electrodes through lund cables. Pole-dipole array was chosen in this study for deeper penetration. Collected data were processed by using RES2DINV software to produce inversion model which was then exported to Surfer8 software for visualisation and interpretation. The result shows that most of the study area consist of granite with different level of fracturing. Unconfined aquifer was found at depths of 0 to 50 m. Confined aquifers can be seen at two different zones. They exhibit same properties at three parallel lines, R1-R3 and show continuity between them. It is predicted that the aquifers flow in the southwest to northeast direction. The hard rock aquifers are highly recommended to be drilled as they contain a large amount of fresh water for further usage.
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Han, Qi, Anna Kelbert, and Xiangyun Hu. "An electrical conductivity model of a coastal geothermal field in southeastern China based on 3D magnetotelluric imaging." GEOPHYSICS 86, no. 4 (2021): B265—B276. http://dx.doi.org/10.1190/geo2019-0446.1.
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The hydrology and geology of the Xinzhou geothermal field in South China and its surrounding area have been well studied. Previous studies have indicated that mantle heat, granite radioactive heat, and partial melting are the likely key thermal sources. However, neither the geometry of the geothermal reservoir nor the groundwater circulation pattern has been fully characterized. Toward that aim, a grid of magnetotelluric (MT) data has been acquired to reveal the subsurface distribution of electrical conductivity and to detect the geothermal reservoir. An analysis of the phase tensors suggests that 3D MT inversion is essential for accurate interpretation of the data. We perform a 3D full-impedance MT inversion and observe pronounced low electrical conductivity zones in the inverse model. We interpret these materials as widely developed granites that form the bedrock, which is cut by a crisscross of faults. The cracks in the bedrock provide pathways for the vertical and lateral movement of the hydrothermal fluid. The geothermal reservoir appears as a prominent high electrical conductivity anomaly beneath the hot spring. A northwest-dipping zone of enhanced electrical conductivity reaching approximately 6–7 km in depth is found in the southeast part of the study area, and it is interpreted as the geothermal reservoir recharge channel. We develop an inferred underground fluid circulation model, informed by the electrical conductivity of the area, in combination with hydrologic data. We suggest that the water supply of the Xinzhou geothermal field mainly comes from meteoric water, which is mixed with the invading seawater and shallow cold groundwater as it rises along the fault. The results of our MT study confirm earlier inferences that the Xinzhou geothermal field belongs to an intraplate deep-circulation type originated from the mantle heat flow.
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Jeje, Julius Olatunji, Muritala Oluwaseun Arowolo, and Adeniyi Ayokunle Sodipo. "Application of Natural Radionuclide in the Subsurface Hydrogeology of Selected Two Local Governments in South Western Nigeria." East African Journal of Engineering 2, no. 1 (2020): 14–22. http://dx.doi.org/10.37284/eaje.2.1.148.
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This research investigated the use of radioactive isotopes to study the underground water characteristics of Ife South and Ife North Local governments area of Osun state in Southwestern Nigeria. The study aimed to determine the origin of water, the flow paths, residence time, and prediction of the geological formation of the study area. Twelve water samples were collected from the two local governments using standard methods for isotope study. Uranium 234U and 238U were analyzed for water samples using a gamma-ray spectrometer with Caesium Iodide (CsI) scintillation detector and physical analyses such as pH, electrical conductivity, total dissolved solids, and temperature were also determined. The specific activity of 238U ranged between 27.44±0.55 to 36.89±1.70 Bq/kg; activity ratio of water samples from the two LGA ranged from 0.83 to 1.07 with average activity ratio of 0.901. All the sample locations have an activity ratio of less than 1.00 except two locations in Ife South LGA (Ooni 1 and 2); a 234U value of 30.386747 Bq/kg was taken as constant. Ife North and Ife South have an average EC, turbidity, TDS, residence time of 493.3 (µs/cm), and 686.6 (µs/cm); 1.2 NTU and 3.33 NTU; 108.67 mg/l and 523.33 mg/l; 2.889 ma and 2.784 ma respectively. In conclusion, the groundwater of the two LGA originate from the same source and are in the oxidation state; aquifers within Ife North and Ife South are separated with a barrier; hence its groundwater does not flow through one another. The residence time of groundwater in the two LGA is over 2.8 ma; Ooni 1 and 2 area is underlain by rocks rich in Uranium (granite), rocks underlying Ife South is younger to Ife North, Ife North is underlying by old weathered rocks (sedimentary rocks).
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Šanda, Martin, and Milena Císlerová. "Transforming Hydrographs in the Hillslope Subsurface." Journal of Hydrology and Hydromechanics 57, no. 4 (2009): 264–75. http://dx.doi.org/10.2478/v10098-009-0023-z.
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Transforming Hydrographs in the Hillslope SubsurfaceTo reveal and evaluate the mechanism of transforming rainfall into runoff in the region, where the subsurface flow plays a dominant role in the runoff formation, a continuous hydrological and climatic data monitoring has been set-up in the experimental catchment Uhlířská (the Jizera Mountains, CR). The soil profile (Dystric Cambisol), formed on the weathered granite bedrock, is shallow and highly heterogeneous. Beside a standard catchment data observation a hillslope transect was instrumented to control the flow dynamics in the soil profile. From three soil horizons, the subsurface outflow is recorded in the subsurface trench. Adjacent to the trench the soil water suction is scanned by triplets of automatic tensiometers. Within the soil profile the unsaturated regime prevails, nevertheless the soil keeps almost saturated. Nearly simultaneous reaction of suction on a rainfall in all soil horizons implies a rapid vertical flow. Local preferential flow paths are conducting infiltrating water at significantly variable rates when saturation is reached. Groundwater table, soil moisture and subsurface runoff measured at the hillslope transect and the total outflow from the catchment, are correlated. The outflow from the catchment is dominantly controlled by soil moisture however the mechanism of its generation is not yet fully understood.
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Martinez-Landa, Lurdes, Jesús Carrera, Andrés Pérez-Estaún, Paloma Gómez, and Carmen Bajos. "Structural geology and geophysics as a support to build a hydrogeologic model of granite rock." Solid Earth 7, no. 3 (2016): 881–95. http://dx.doi.org/10.5194/se-7-881-2016.
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Abstract. A method developed for low-permeability fractured media was applied to understand the hydrogeology of a mine excavated in a granitic pluton. This method includes (1) identifying the main groundwater-conducting features of the medium, such as the mine, dykes, and large fractures, (2) implementing this factors as discrete elements into a three-dimensional numerical model, and (3) calibrating these factors against hydraulic data . A key question is how to identify preferential flow paths in the first step. Here, we propose a combination of several techniques. Structural geology, together with borehole sampling, geophysics, hydrogeochemistry, and local hydraulic tests aided in locating all structures. Integration of these data yielded a conceptual model of the site. A preliminary calibration of the model was performed against short-term (< 1 day) pumping tests, which facilitated the characterization of some of the fractures. The hydraulic properties were then used for other fractures that, according to geophysics and structural geology, belonged to the same families. Model validity was tested by blind prediction of a long-term (4 months) large-scale (1 km) pumping test from the mine, which yielded excellent agreement with the observations. Model results confirmed the sparsely fractured nature of the pluton, which has not been subjected to glacial loading–unloading cycles and whose waters are of Na-HCO3 type.
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XU, Y. F., and X. Y. LI. "FRACTAL APPROACH TO EROSION THRESHOLD OF BENTONITES." Fractals 26, no. 02 (2018): 1840012. http://dx.doi.org/10.1142/s0218348x18400121.
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Bentonite has been considered as a candidate buffer material for the disposal of high-level radioactive waste (HLW) because of its low permeability, high sorption capacity, self-sealing characteristics and durability in a natural environment. Bentonite erosion caused by groundwater flow may take place at the interface of the compacted bentonite and fractured granite. Surface erosion of bentonite flocs is represented typically as an erosion threshold. Predicting the erosion threshold of bentonite flocs requires taking into account cohesion, which results from interactions between clay particles. Beyond the usual dependence on grain size, a significant correlation between erosion threshold and porosity measurements is confirmed for bentonite flocs. A fractal model for erosion threshold of bentonite flocs is proposed. Cohesion forces, the long-range van der Waals interaction between two clay particles are taken as the resource of the erosion threshold. The model verification is conducted by the comparison with experiments published in the literature. The results show that the proposed model for erosion threshold is in good agreement with the experimental data.
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Rivas-Perez, J., E. L. Tullborg, and S. A. Banwart. "The kinetics of O2(aq) reduction during oxidative weathering of naturally occurring fracture minerals in groundwater." Mineralogical Magazine 67, no. 2 (2003): 399–414. http://dx.doi.org/10.1180/0026461036720108.
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Aqueous chemistry methods assessed the kinetic reactivity and reduction capacity of fracture-filling minerals from a granitic groundwater environment at the Aspo Hard Rock Laboratory, a field station for research and development into the geological disposal of spent nuclear fuel. Naturally occurring fracture filling reacted with oxygenated test solutions of known composition in recirculating batch reactors.The loss of O2(aq) with time was consistent with second-order reaction kinetics where O2(aq) is consumed through reduction by reaction with structural Fe(II) at the surface of the fracture minerals. Values of the second-order rate constant (k, l mole—1 h—1) varied between experiments within the range 1.7 < log k < 2.9 and values for the total concentration of reducing sites as a measure of the reduction capacity of the mineral (St, mole g—1) varied within the range 8.5 x 10—5 < St < 4.3 x 10—4. Values for the rate constant are somewhat less than those published previously for reaction between O2(aq) and Fe(II) surface complexes; i.e. structural Fe(II) appears to be less reactive than adsorbed Fe(II)(aq) but is significantly more reactive than Fe2+.Values of the rate constant did not depend on release of network ions from the reacting minerals, and did not vary significantly with pH, mineral mass, specific surface area or mineral Fe(II) content. Oxidative weathering of sulphide minerals does not occur to any measurable extent. When corrected to rock/water ratios for granite aquifers, the rate constants correspond to a half-life for O2(aq) on the order of seconds indicating an essentially instantaneous reaction on repository time scales. Comparison of reducing capacity for the fracture fillings and oxidizing capacity for groundwater saturated with O2(aq) indicates that oxidizing fronts within the geological barrier would travel ~4000 times more slowly than the velocity of groundwater flow.
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Wang, Xiao, Guoping Lu, and Bill X. Hu. "Hydrogeochemical Characteristics and Geothermometry Applications of Thermal Waters in Coastal Xinzhou and Shenzao Geothermal Fields, Guangdong, China." Geofluids 2018 (January 31, 2018): 1–24. http://dx.doi.org/10.1155/2018/8715080.
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Two separate groups of geothermal waters have been identified in the coastal region of Guangdong, China. One is Xinzhou thermal water of regional groundwater flow system in a granite batholith and the other is thermal water derived from shallow coastal aquifers in Shenzao geothermal field, characterized by high salinity. The hydrochemical characteristics of the thermal waters were examined and characterized as Na-Cl and Ca-Na-Cl types, which are very similar to that of seawater. The hydrochemical evolution is revealed by analyzing the correlations of components versus Cl and their relative changes for different water samples, reflecting different extents of water-rock interactions and clear mixing trends with seawaters. Nevertheless, isotopic data indicate that thermal waters are all of the meteoric origins. Isotopic data also allowed determination of different recharge elevations and presentation of different mixing proportions of seawater with thermal waters. The reservoir temperatures were estimated by chemical geothermometries and validated by fluid-mineral equilibrium calculations. The most reliable estimates of reservoir temperature lie in the range of 148–162°C for Xinzhou and the range of 135–144°C for Shenzao thermal waters, based on the retrograde and prograde solubilities of anhydrite and chalcedony. Finally, a schematic cross-sectional fault-hydrology conceptual model was proposed.
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Smith, Steven, and Roel Snieder. "Seismic modeling and analysis of a prototype heated nuclear waste storage tunnel, Yucca Mountain, Nevada." GEOPHYSICS 75, no. 1 (2010): T1—T8. http://dx.doi.org/10.1190/1.3273868.
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We have developed seismic velocity models for the heated rock surrounding a tunnel in Yucca Mountain tuff and compared the results with field data obtained at the Yucca Mountain drift scale test (DST) facility from 1998 to 2002. During that time, the tunnel was heated to replicate the effects of long-term storage of decaying nuclear waste and to study the effects of extreme temperatures on the surrounding rock and groundwater flow. Our velocity models are based on borehole temperature data, thermal models, and laboratory measurements on granite. Comparisons between field and synthetic seismograms show that superheating the rock around the tunnel causes thermally induced variations in P- and S-wave arrival-time separation. Barring out-of-plane reflections, 2D spectral element waveform modeling in the source plane consistently replicates seismic receiver waveforms and classic behavior of pulses reflected from cylinders. Our models constrain the in situ [Formula: see text] velocity/temperature derivative of the tuff to be approximately [Formula: see text] per [Formula: see text]. This velocity change is consistent with thermally induced wavespeed changes in dry rock samples and is lower than expected for water-to-steam conversion in saturated rock. We infer that velocity changes are controlled by thermal expansion and fracturing. Additionally, we have developed an improved method for monitoring tunnel conditions that uses waves diffracted around the tunnel in the region of changing velocity.
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Xu, Qiang, Dalei Peng, Weile Li, et al. "The catastrophic landfill flowslide at Hongao dumpsite on 20 December 2015 in Shenzhen, China." Natural Hazards and Earth System Sciences 17, no. 2 (2017): 277–90. http://dx.doi.org/10.5194/nhess-17-277-2017.
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Abstract. A catastrophic flowslide occurred at the Hongao dumpsite on 20 December 2015 in the Guangming New District of Shenzhen, China. The flowslide caused 77 causalities and damaged 33 buildings. In the absence of extreme weather conditions and seismic activity, the causes of the failure were analyzed on the basis of multi-temporal remote-sensing images, site investigation, in situ tests, laboratory tests, and numerical analyses. Site investigations showed that the volume of the displaced material was 2.32 × 106 m3 and the volume of the pre-failure waste filling was 6.27 × 106 m3. The flowslide was characterized by high travel velocity and long runout distance. The displaced material was primarily a mixture of silty soil and construction and demolition waste with water content of 17.3–42.4 %. The primary causes of the failure were concluded to be the following: (1) groundwater flow had stagnated in the dumpsite due to drainage system failure and the underlying impermeable granite stratum; (2) the accumulation rate and total volume of the waste filling was in exceedance of the design capacity. The flowslide may be ascribed to the development of excess pore-water pressure as evidence of liquefaction was observed at several locations, and it is postulated that such phenomena were related to the surcharge loads imposed by the unregulated disposal activities.
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Baxter, S., D. Holton, S. Williams, and S. Thompson. "Predictions of the wetting of bentonite emplaced in a crystalline rock based on generic site characterization data." Geological Society, London, Special Publications 482, no. 1 (2018): 285–300. http://dx.doi.org/10.1144/sp482.8.
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AbstractA geological disposal facility (GDF) is the widely accepted long-term solution for the management of higher-activity radioactive waste. It consists of an engineered facility constructed in a suitable host rock. The facility is designed to inhibit the release of radioactivity by using a system consisting of engineered and natural barriers. The engineered barriers include the wasteform, used to immobilize the waste, the waste disposal container and any buffer material used to protect the container. The natural barrier includes the rocks in which the facility is constructed. The careful design of this multi-barrier system enables the harmful effects of the radioactivity on humans and biota in the surface environment to be reduced to safe levels.Bentonite is an important buffer material used as a component of a multi-barrier disposal system. For example, compacted bentonite rings and blocks are used to protect the copper container, used for the disposal of spent fuel, in the KBS-3 disposal system. As the bentonite saturates, through contact with groundwater from the host rock, it swells and provides a low hydraulic conductivity barrier, enabling the container to be protected from deleterious processes, such as corrosion. The characteristic swelling behaviour of bentonite is due to the presence of significant quantities of sodium montmorillonite.Recently, there have been detailed in situ experiments designed to understand how bentonite performs under natural conditions. One such experiment is the Buffer–Rock Interaction Experiment (BRIE), performed at the Äspö Hard Rock Laboratory near Oskarshamn in the SE of Sweden. This experiment is designed to further understand the wetting of bentonite from the groundwater flow in a fractured granite host rock.In this paper, the observations from the BRIE are explained using an integrated model that is able to describe the saturation of bentonite emplaced in a heterogeneous fractured rock. It provides a framework to understand the key processes in both the rock and bentonite. The predictive capability of these models was investigated within the context of uncertainties in the data and the consequence for predictions of the wetting of emplaced bentonite. For example, to predict the wetting of emplaced bentonite requires an understanding of the distribution of fracture transmissivity intersecting the bentonite. A consequence of these findings is that the characterization of the fractured rock local to the bentonite is critical to understanding the subsequent wetting profiles. In particular, prediction of the time taken to achieve full saturation of bentonite using a simplified equivalent homogeneous description of the fractured host rock will tend to be too short.
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Thomas, M. D., and C. Willis. "Gravity modelling of the Saint George Batholith and adjacent terrane within the Appalachian Orogen, southern New Brunswick." Canadian Journal of Earth Sciences 26, no. 3 (1989): 561–76. http://dx.doi.org/10.1139/e89-048.
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The geometry of the Saint George Batholith has been investigated along three detailed (1–2 km station spacing) north–south gravity traverses surveyed in conjunction with a geothermal study. Modelling of corresponding gravity profiles indicates that the batholith is 6.6, 4.3, and 7.0 km thick along the western, central, and eastern traverses, respectively. The western profile crosses the buried western granitic extension of the batholith and the exposed mafic Bocabec complex, modelled as a sheet 200–400 m in thickness. The central profile crosses the western half of the exposed batholith, and the eastern profile crosses the eastern half near a borehole used for heat-flow measurements.Two other gravity profiles, defined by detailed and regional (average station spacing about 5 km) observations, were also modelled. One trends northeast across the eastern margin of the batholith and passes directly through the borehole site, at which the batholith is modelled as 6.5 km thick. Here, geothermal calculations suggest that the thickness of radiogenic granite lies in the range 1.4–3.3 km. The large discrepancy between gravity and geothermal estimates supports suggestions that radiogenic elements have been concentrated in the upper part of the batholith, probably by circulating groundwater. The second profile crosses the Pleasant Ridge and Sorrel Ridge granitic intrusions, located northwest of the batholith. Modelling indicates that these intrusions are rooted in the buried roof of the Saint George Batholith at depths of about 1.1 km.Relatively high levels of the gravity field south of the batholith are attributed to dense Precambrian rocks, which are modelled as forming the wall rocks along much of the southern margin of the batholith. The walls in places are steep, suggesting control by major faults that step the Precambrian rocks down to the north, where they apparently floor the batholith and (or) lower Palaeozoic rocks at a depth of about 7.6 km. This picture of block faulting is supported by interpretation of a regional gravity profile located northeast of the Saint George Batholith and running northwest from the Bay of Fundy to the Miramichi Massif.
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Matos, A. P., and C. Alves. "Multivariate statistical analysis of hydrogeochemical data towards understanding groundwater flow systems in granites." Quarterly Journal of Engineering Geology and Hydrogeology 49, no. 2 (2016): 132–37. http://dx.doi.org/10.1144/qjegh2016-006.
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La Licata, Ivana, Loris Colombo, Vincenzo Francani, and Luca Alberti. "Hydrogeological Study of the Glacial—Fluvioglacial Territory of Grandate (Como, Italy) and Stochastical Modeling of Groundwater Rising." Applied Sciences 8, no. 9 (2018): 1456. http://dx.doi.org/10.3390/app8091456.
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On November 2014, the Municipality of Grandate, near Lake Como, had to deal with a great emergency that was caused by the flooding of factory undergrounds. The authors realized a hydrogeological study to understand the causes of groundwater flooding and to prepare a pre-feasibility study concerning possible actions for groundwater control. The hydrogeological structure is rather complex and required time-consuming reconstruction of the conceptual site model. A transient numerical model was developed to analyse the system behaviour in different scenarios. The flow model was calibrated in a steady and unsteady-state using the automatic calibration code Model-Independent Parameter Estimation (PEST). The study demonstrated that the reason for floods was mainly due to the concurrence of three causes: (1) the hydrogeological structure of the area was recognized as a stagnation zone, (2) groundwater rising, and (3) extremely heavy rainfall in 2014. Through the PEST RandPar function, 100 random rainfall scenarios were generated starting from rainfall data for the last 20 years. The model was used to run 100 1-year long simulations considering the probability distribution of recharge related to the 100 randomly generated rainfall scenarios. Through collecting the piezometric heads that resulted from the simulations, monthly probability curves of groundwater exceeding a threshold level were obtained. The results provided an occurrence probability of groundwater level exceeding the underground structures level between 12% and 15%.
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Emerman, Steven H., Janae R. Nelson, J. Kade Carlson, Tracy K. Anderson, Anusha Sharma, and Basanta R. Adhikari. "The effect of surface lithology on arsenic and other heavy metals in surface water and groundwater in Mustang Valley, Nepal Himalaya." Journal of Nepal Geological Society 47, no. 1 (2014): 1–21. http://dx.doi.org/10.3126/jngs.v47i1.23100.
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Recent studies have shown that elevated groundwater as occurs even in Kathmandu and Pokhara Valleys in Nepal, two tectonic valleys well upstream of the floodplain of the Ganges River. Moreover, studies in both valleys showed surface water As to be statistically indistinguishable from groundwater As, which led to the fluvial recharge model in which elevated groundwater As results from losing streams with elevated As, which is a consequence of rapid erosion caused by a combination of monsoon climate, tectonic uplift and deforestation. The objective of this study was to further test the fluvial recharge model in Mustang Valley, the third major tectonic valley in Nepal Himalaya far upstream from the floodplain of the Ganges River. In May 2011 water samples were collected from 33 surface water sites (24 directly from streams and 9 from canals, pipes or taps fed by streams) and 24 groundwater sites (10 directly from springs and 14 from pipes or taps fed by springs). The WHO As Standard was exceeded in 47% of surface water samples and 79% of groundwater samples, including all nine functioning water taps in Lo-Manthang, the largest village. Separating samples into a high- As Region I (geometric mean As = 0.071 mg/L) and a low-As Region II (undetectable As for 85% of samples) showed that surface water As and groundwater As were statistically indistinguishable within each region. Only Region I receives overland flow from the exposed Mustang and Mugu Granites. The correspondence between groundwater As and watershed surface lithology is further evidence for the fluvial recharge model.
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Sukhija, B. S., D. V. Reddy, P. Nagabhushanam, S. K. Bhattacharya, R. A. Jani, and Devender Kumar. "Characterisation of recharge processes and groundwater flow mechanisms in weathered-fractured granites of Hyderabad (India) using isotopes." Hydrogeology Journal 14, no. 5 (2005): 663–74. http://dx.doi.org/10.1007/s10040-005-0461-6.
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Funabiki, Ayako, and Masahito Oguma. "Effects of Groundwater Flow on a Ground Source Heat Pump System." Journal of Thermal Science and Engineering Applications 9, no. 2 (2017). http://dx.doi.org/10.1115/1.4035502.
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Heat advection by groundwater flow is known to improve the performance of ground heat exchangers (GHEs), but the effect of groundwater advection on performance is not yet fully understood. This numerical study examined how parameters related to groundwater flow, such as aquifer thickness, porosity, lithology, and groundwater flow velocity, affected the performance of a borehole GHE. Under a thin-aquifer condition (10 m, or 10% of the entire GHE length in this study), groundwater flow velocity had the greatest effect on heat flux. At a groundwater flow velocity of at least 10−4 m/s through a low-porosity aquifer filled with granite gravel with high thermal conductivity, the heat flux of a GHE was as much as 60% higher than that of a GHE in a setting without an aquifer. If the aquifer was as thick as 50 m, the high thermal conductivity of granite gravel doubled the heat flux of the GHE at a groundwater flow velocity of at least 10−5 m/s. Thus, not only groundwater flow velocity but also aquifer thickness and thermal conductivity were important factors. However, groundwater seldom flows at such high velocities, and porosity, gravel size and composition, and aquifer thickness vary regionally. Thus, in the design of ground source heat pump systems, it is not appropriate to assume a large groundwater effect.
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Mokrik, Robert, Vytautas Samalavičius, Marius Gregorauskas, and Modestas Bujanauskas. "Environmental isotopes and noble gas ages of the deep groundwater with coupled flow modelling in the Baltic artesian basin." Lithuanian Journal of Physics 61, no. 1 (2021). http://dx.doi.org/10.3952/physics.v61i1.4407.
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In this study, modelled groundwater actual flow times in intermediate and deep aquifers, covered by regional scale impermeable aquitards, were compared with 4He and 81Kr age dating results. To improve the reliability of the steady state 3D groundwater flow model, the isotopic ages of deep groundwater were compared to the MODPATH modelled travel times. The highest helium values in groundwater reservoirs coincide with fault zones in the crystalline basement and sedimentary cover near Rapakivi granite massifs. Insights into isotope-geochemical anomalies of the Baltic Artesian Basin intermediate and deep groundwater support their main distribution peculiarities in the flow path towards the Baltic Sea coast lowland and seabed depression as the regional groundwater discharge area.
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Quiñones, J., J. Garcia Serrano, J. A. Serrano, P. Diaz Arocas, J. L. Rodriguez, and J. Blazquez. "Modelling UO2 and Simfuel Leaching Behaviour in Granite Groundwater Under Oxidizing Conditions." MRS Proceedings 556 (1999). http://dx.doi.org/10.1557/proc-556-479.
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AbstractThe Uranium concentration leaching behaviour for UO2 and SIMFUEL in granite groundwater under oxidizing conditions is modelled. The model contemplates two terms: a source term and a loss term. The source term represents the bulk dissolution process and its upper limit is controlled by the solubility of the thermodynamically stable solid phase. The loss term emulates the solute removed due to groundwater flow into the repository. It can forecast the uranium steady state concentration when groundwater flow is considered. The model has been tested with three different types of leaching experiments, performed with UO2 and SIMFUEL. Good agreement between experimental results and model predictions are found.
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Arthur, Randy, Teruki Iwatsuki, Katsuhiro Hama, Kenji Amano, Richard Metcalfe, and Kunio Ota. "The Redox Environment of Deep Groundwaters Associated with the Tono Uranium Deposit, Japan." MRS Proceedings 713 (2002). http://dx.doi.org/10.1557/proc-713-jj8.3.
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ABSTRACTAn unconformity underlying the Tono uranium deposit in central Japan represents the approximate location of a redox front separating relatively oxidizing groundwaters (Eh ≈0 mV) in the weathered, fractured Toki granite (TG) from strongly reducing pore fluids (Eh ≈-360 mV) in sedimentary rocks of the overlying Lower Toki Lignite-bearing Formation (TL). Uranium has been effectively immobilized in the TL during the past 10 million years. Stable and reversible redox potentials measured in-situ in boreholes penetrating the sedimentary rocks and granite appear to be controlled by the Fe(III)-oxyhydroxide – Fe2+ redox couple. A simplified analytical model of front migration suggests that chemical buffering by pyrite alone would limit the propagation velocity of the front into the TL to less than 8x10−6 m yr−1. The model is constrained by Darcy fluxes derived from groundwater flow models and relative 14C groundwater ages, average modal abundances of pyrite in the TL, and the analytical detection limit for dissolved oxygen in TG groundwaters (2 ppm). Model results also suggest that the redox buffering capacity of the TL would be exhausted within 10 million years if an upper bound O2(aq) concentration in TG groundwaters fixed by equilibrium with atmospheric O2(g) (8.5 ppm) is assumed. Immobilization of uranium in the TL is thus attributable to oxidation-reduction reactions that minimize O2(aq) concentrations primarily in the TG, and secondarily in the TL.
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Bros, Regis, Yoji Seki, Atsushi Kamei, Yutaka Kanai, Koichi Okuzawa, and Yoshio Watanabe. "Geochemical Approaches to Understanding a Shallow Groundwater Flow in the Kanamaru Uranium Mineralization Area (Japan)." MRS Proceedings 893 (2005). http://dx.doi.org/10.1557/proc-0893-jj09-07.
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AbstractPredicting the behaviour of radioactive wastes can be facilitated by comparison with the evolution of natural groundwater systems. During a study of the Kanamaru U mineralization (Japan), geochemical approaches for understanding a shallow (0-50 m) fresh groundwater flow system are being assessed. Deep granitic waters are Ca-HCO3-dominated and slightly acidic to slightly alkaline. Shallow waters within sediments display lower pH and they are more dilute. Halide concentrations suggest the existence of a non marine Br-rich and Cl-depleted deep groundwater in the basement. 234U/238U and 230Th/234U activity ratios in the mineralized sedimentary rocks indicate that U mobilization took place within the last 350,000 years. U dissolution currently continues and it is controled by lateral groundwater flow whereas vertical diffusion appears negligible. Dissolved alkaline earths concentrations and the 87Sr/86Sr ratio indicate that solutes exchanges take place through uppermost low permeable granite followed by mixing with more dilute and Cl-type shallow groundwater.
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Naves, Acacia, Javier Samper, Bruno Pisani, et al. "Hydrogeology and groundwater management in a coastal granitic area with steep slopes in Galicia (Spain)." Hydrogeology Journal, May 5, 2021. http://dx.doi.org/10.1007/s10040-021-02349-5.
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AbstractGroundwater availability, management and protection are great challenges for the sustainability of groundwater resources in the scattered rural areas of the Atlantic regions of Europe where groundwater is the only option for water supply. This report presents a hydrogeological study of the coastal granitic area of Oia in northwestern Spain, which has unique geomorphological and hydrogeological features with steep slopes favoring the erosion of the weathered granite. The hydrogeological conceptual model of the study area includes: (1) the regolith layer, which is present only in the flat summit of the mountains; (2) the slope debris and the colluvial deposits, which are present in the intermediate and lowest parts of the hillside; (3) the marine terrace; and (4) the underlying fractured granite. Groundwater recharge from rainfall infiltration varies spatially due to variations in terrain slope, geology and land use. The mean annual recharge estimated with a hydrological water balance model ranges from 75 mm in the steepest zone to 135 mm in the lowest flat areas. Groundwater flows mostly through the regolith and the detrital formations, which have the largest hydraulic conductivities. Groundwater discharges in seepage areas, springs, along the main creeks and into the sea. The conceptual hydrogeological model has been implemented in a groundwater flow model, which later has been used to select the best pumping scenario. Model results show that the future water needs for domestic and tourist water supply can be safely provided with eight pumping wells with a maximum pumping rate of 700 m3/day.
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"Stochastic discrete fracture simulation of groundwater flow into an underground excavation in granite." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 24, no. 5 (1987): 185. http://dx.doi.org/10.1016/0148-9062(87)90969-7.
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Niibori, Yuichi, Kyo Komatsu, and Hitoshi Mimura. "Deposition of Calcium-Silicate-Hydrate Gel on Rough Surface of Granite from Calcium-rich Highly Alkaline Plume." MRS Proceedings 1475 (2012). http://dx.doi.org/10.1557/opl.2012.598.
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ABSTRACTCement-based materials used in the construction of the repository for high/low level radioactive wastes may produce a highly alkaline calcium-rich groundwater (plume). The Ca ions react with soluble silicic acid, depositing calcium-silicate-hydrate (CSH) gel on the surfaces of the groundwater flow-paths and decreasing the permeability of the bedrock. Such a decrement of permeability may play a role in retarding the migration of radionuclides. In this study, the deposition behavior in a fracture was experimentally examined by using a micro flow-cell consisting of silicon plate (including a slit (60 mm×5 mm, or 60 mm×2 mm)) and granite-chip. The initial equivalent-aperture based on the square law was estimated in the range of 26 μm to 45 μm from the flow test of pure water.In the experiments, a Ca(OH)2 solution of 6.36 mM (pH: 12.2 to12.5, including NaOH) was continuously injected into the flow system at a constant flow rate of 1 or 2 ml/h. The solution flowed on the surface of the granite-chip. In this study, we prepared two kinds of chips that differed in the treatment of the surface. One chip was roughly ground with #2000 sandpaper (hereinafter referred to as rough surface) and another was polished to mirror-like surface. As a result, on the rough surface the deposits of CSH gel appeared along flow-channels across mineral grain-boundaries, while the deposits on the mirror-like surface were relatively uniform. Furthermore, the permeability in the case of rough surface became smaller than that in the case of mirror-like surface, showing the repeats of rapid decrement and increment due to the relatively large roughness of the surface. In order to estimate the decrement degrees of permeability, a simple, one-dimensional mathematical model is proposed in this study.
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Morikawa, Noritoshi. "Dissolved helium distribution in deep groundwaters from the Tono area, central Japan: a tool for tracing groundwater flow in fractured granite." Limnology 5, no. 2 (2004). http://dx.doi.org/10.1007/s10201-004-0118-5.
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Kotowsk, Jaroslav, Tomáš Černoušek, Filip Jankovský, et al. "Development of Experimental Instrumentation for Measurement of Advection in Narrow Aperture in Granite Block." Journal of Nuclear Engineering and Radiation Science 5, no. 3 (2019). http://dx.doi.org/10.1115/1.4041790.
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A granite block, acquired from a quarry Panská Dubenka located in the Czech Republic and used in presented experiments, is part of the same bedrock that can be potentially used for a deep geological repository. It is important to characterize advection in fractured rock to assess possible groundwater contamination. Newly used method—three-dimensional scanning using Hexagon Romer Arm was implemented to characterize the morphology of an examined fractured block with a aperture. The scanning technology provides the possibility to digitalize the rock surface. The scanning can be also used to determine any changes in the rock surface. The block was instrumented by tubing, and the aperture was sealed using a silicone. Flow paths were investigated by the comparison of fluid weights on the outlet on every output/site. The Hexagon Romer Arm is an ideal tool for the precise determination of a aperture's width in its full volume.
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Vandergraaf, Tjalle T., D. M. Grondin, and D. J. Drew. "Laboratory Radionuclide Migration Experiments at a Scale of 1 m." MRS Proceedings 112 (1987). http://dx.doi.org/10.1557/proc-112-159.
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AbstractResults are presented from a migration experiment carried out in a natural fracture in a 1 m × 1 m × 0.6 m quarried granite block. Near-uniform flow in the fracture was achieved by controlling the groundwater flow from the fracture laterally across the exit face of the fracture. The longitudinal dispersion was determined from the elution profile of uranine, a non-sorbing tracer. The effect of matrix diffusion was determined by reducing the linear velocity of the transport solution from approximately 3 to 0.75 cm/h. The velocity of a sorbing tracer, Cs-137, was compared to that of non-sorbing I-131 and with that calculated from data obtained for Cs-137 in static sorption experiments on similar fracture surfaces. Information on channeling in the fracture was obtained by autoradiographing the fracture surface of the separated block after the termination of the experiment. Quantitative information on the sorbed Cs-137 inventory by two-dimensional gamma scanning of the fracture surfaces is underway.
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Augusto Moreira, César, Carolina Gonçalves Leandro, Camila Trindade Lopes, and Lenon Melo Ilha. "DC resistivity investigation in a fractured aquifer system contaminated by leachate from an old dump." Geofísica Internacional 56, no. 4 (2017). http://dx.doi.org/10.22201/igeof.00167169p.2017.56.4.1827.
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The dumps are areas of final disposal of solid wastes directly into the soil, with no technical criteria or collecting systems of gases or liquids. A large part of Brazilian municipalities have used this extreme damaging alternative to the environment up to the year 2010, when a federal law made compulsory the installation of sanitary landfills. However, large parts of the dumps were simply abandoned, although some eventually go through treatment after assessments of the state environmental agencies. This work presents the results of a geophysical investigation in a dump deactivated in 2004 in a small city in southern Brazil, where previous investigations have revealed contamination of soil and groundwater by leachate. Structural analyzes in the area of study combined to geological data from monitoring wells indicate the presence of contaminants in fractured granite, with a wide variation in the thickness of soil, saprolite and groundwater level. The integration of chemical analyses of the groundwater with electrical resistivity tomography (ERT) in 2D and 3D processing, revealed the existence of large contaminated areas within the limits of the dump flowing into the aquifer partially free up to 5m depth. Such areas may decrease gradually with the increase in depth and between 9m and 19m contaminated zones clearly predominate, associated with the flow in the fractured aquifer. The indication of restricted and oriented zones suggests the targeting and accumulation of contaminants in two systems of preferential fractures. The discovery of these zones is fundamental for planning and the installation of pumping and decontamination systems of groundwater, considering a declining production of leachate since the closure of the dump.
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Hoover, James D., and Edward C. Thornton. "Sizing Requirements for Flow-Through Geochemical Tests: Theoretical Considerations and Model Results." MRS Proceedings 176 (1989). http://dx.doi.org/10.1557/proc-176-683.
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ABSTRACTA methodology for evaluating test apparatus size requirements has been applied to the sizing of flow-through tests used in the evaluation of coupled reaction and transport processes. The results of the sizing evaluation constrain the apparatus dimensions and test conditions capable of yielding results representative of the processes of interest.The size requirements of flow-through tests involving a system of simplified granite and groundwater were determined in order to demonstrate the feasibility and implications of sizing evaluations. Reaction path simulations were performed using the E03/6 codes at temperatures of 25°C, 100°C, and 200°C. The determination of reaction path as a function of time was then used to obtain minimum column residence time requirements. Simulation results indicate that column lengths required for development of quasistatic equilibrium reaction zones at 200°C are three times smaller than at 100°C, and over 36 times smaller than at 25°C.A range of possible combinations of column dimensions and flow rates for a set of model test conditions exist for a given residence time. The most appropriate combinations depend on the purpose of the test, the process of interest, and factors such as test duration, sampling requirements, and engineering limitations. Size and scale evaluations thus provide a technical basis for the design and construction of flow-through tests, and have profound implications for the interpretation of test results.
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Cancelo-González, Javier, Diego Martiñá Prieto, Remigio Paradelo, and María Teresa Barral. "A microcosm study of permeable reactive barriers filled with granite powder and compost for the treatment of water contaminated with Cr (VI)." Spanish Journal of Soil Science 5 (July 14, 2015). http://dx.doi.org/10.3232/sjss.2015.v5.n2.07.
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The permeable reactive barrier (PRB) is a technology developed for the removal of contaminants in groundwater. It consists of a screen perpendicular to the flow of contaminated groundwater filled with a material capable of adsorbing, precipitating or degrading pollutants. Several materials have been tested for their use as reactive substrates for the construction of PRBs. Waste materials are of particular interest for this purpose due to the possibility of their reuse and their generally lower cost. With this aim, the Cr (VI) retention capacity of filler material consisting either of pine bark compost (PB) or a 50% mixture of compost and granite powder (PB50) was evaluated using an experimental device specifically designed for this study, which reproduces a permeable reactive barrier at the laboratory scale. Percolation experiments were carried out with a solution of 100 mg L<sup>-1</sup> Cr (VI) in 0.01M KNO<sub>3</sub>, followed by a leaching step with the saline background. The results show that compost is a highly efficient filler for permeable reactive barriers with almost 100% retention of Cr, whereas the retention efficiency of the mixture of PB50 oscillated between 18 and 46% during the experiment. The Cr retained by the filling material is strongly fixed, since no desorption was detected by leaching with the saline background, and concentrations in the standard Toxic Characteristic Leaching Procedure (TCLP) extracts were lower than 1 mg L<sup>-1</sup>. This behaviour minimizes the risk of release of the Cr retained by the material of the barrier in the event of it being traversed by water not contaminated with Cr. Modelling with Visual Minteq indicates that in the experiments with PB, the reduction of Cr (VI) to Cr (III) occurs and that Cr (III) is associated with dissolved organic matter, which is a form of lower toxicity than the initial Cr (VI) species. In turn, in the experiments with PB50, Cr (III) and Cr (VI) coexist and the oxidised form is not associated with dissolved organic matter, which suggests greater toxicity. The results indicate that pine bark compost is a potential candidate for use as filler material permeable reactive barriers.
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Rebelo 1, Antonio M. A., André V. L. Bittencourt, and Luiz E. Mantovani. "MODELOS DE EXALAÇÃO DE RADÔNIO EM PAISAGENS TROPICAIS ÚMIDAS SOBRE GRANITO." Boletim Paranaense de Geociências 52 (June 30, 2003). http://dx.doi.org/10.5380/geo.v52i0.4201.
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Foram estabelecidas e analisadas as principais relações entre intensidades de exalação de radônio ( 222Rn e 220Rn) e os elementos morfológicos e dinâmicos de paisagens tropicais úmidas, com o objetivo de elaborar modelos de exalação de Rn adaptados a este tipo de paisagens, e aplicáveis na escala de pequenos núcleos habitacionais. Em uma vertente sobre rocha granítica com teores normais em U e Th, e caracterizada pela associação Latossolo-Solo Podzólico, os produtos de atuação dos processos supergênicos, com destaque para a transição de latolização em podzolização, e o atual regime hídrico do aqüífero freático, foram relacionados aos processos radioativos de geração, emanação e migração de Rn, verificando-se como tais inter-relações afetam a sua exalação nas paisagens. Tal abordagem foi fundamentada nos conceitos de sistema pedológico de transformação e de geoquímica de paisagens, além de conceitos da física e geologia nucleares e elementos climatológicos e hidrogeológicos do macroambiente, num enfoque interdisciplinar, tridimensional e sistêmico. Às vertentes configuradas em paisagens elementares; eluvial, transeluvial e supraqual associam-se diferentes geoformas, tipos e espessuras de solos residuais e radioanomalias com diferentes intensidades e formas de hospedagem de U e de Th. Com base em tais elementos, suas relações espaciais com o sistema freático, e considerando a umidade dos solos na capacidade de campo, as possibilidades de maiores taxas de exalação de Rn, sobretudo 222Rn, são nas paisagens supraqual e transeluvial. Na paisagem eluvial, a despeito da existência de intensas anomalias gama, devido principalmente ao acúmulo de minerais resistatos com U e Th e compostos de Th, os fluxos de Rn são menos significativos. Assim, no contexto enfocado, os produtos da alteração supergênica, organizados num sistema vertente, são materiais em que as taxas de exalação de radônio são mais elevadas do que as medidas na rocha inalterada subjacente. O entendimento do comportamento do U, Th, Ra e Rn no ambiente superficial tornou possível estabelecer modelos previsionais de exalação de Rn adaptados às paisagens elementares, em escalas compatíveis com pequenos núcleos habitacionais ou em unidades residenciais. RADON EXHALATION MODELS IN HUMID TROPICAL LANDSCAPES OVER GRANITE Extended Abstract The main relationships between radon ( 222 Rn and 220 Rn) exhalation intensities and the morpho-dynamic elements of humid tropical landscapes have been established and analyzed, aiming at elaborating Rn exhalation models adapted to this type of landscapes, to be used in the scale of small habitational nuclei. The present research revolved around the understanding of two distinct phases, each one presenting their own processes and time durations. The first one covers the modelling and internal constitution of a drainage basin slopes, during the geologic and pedologic times. The second one refers to the slope morphological system, structure of which is the result of previous processes, allowing for the current radioactive processes of Rn generation, emanation (figure 1), migration and exhalation, some of which affected by rain, temperature, pressure and winds. Such elements have proven to be relevant in the water regimen of the phreatic aquifer. Multi and interdisciplinary studies about the different areas approached were done, making use of several data, information and concepts from worldwide scientific literature. The focus of the study has been a slope over granite containing normal levels of U and Th, and characterized by the soil association Latosol-Podzolic (figure 2). The analyses were carried out in short spatial-temporal limits, according to the dimensions of the slopes, and, regarding time specifics, the pedologic scale was found to be the most relevant. Several aspects have been evaluated, namely the role of the supergenic processes on the evolution of the landscapes, the impact of this evolution on the efficiency of the radioactive processes mentioned, on the different soils and under different aquifer hydric regimens in these landscapes. In the studied soil, emphasis was placed on the concept of the transformation pedologic system and on the relative cronology of the main pedogenetic phases involved, namely latolization and podzolization. In the dispersion of radionuclides, fundamental concepts of surface geochemistry have been used, main emphasis on the ones of elementary landscape geochemistry (figure 2), and of element abundance, migration, flows, and geochemical barriers, backed up by the use of Th/U and Us/Ut (exchageable U/total U) ratios. Moreover, several concepts of nuclear physics, main focus on the 238 U and 232 Th decay series, and hydrogeologic and climatological elements of the environment have been addressed. In regard to the spatial-temporal dimensions stressed in this study, the chronology of the main pedogeochemical processes responsible for the re-distribution of U and Th, and the nature of their secondary hosting phases, it was assumed that the radionuclides of the series mentioned are in secular radioactive equilibrium. Such an approach allowed for the use of U and Th as indicators of the distribution of Ra, Rn precursor, which, in this study, is symbolized by the notation U and Th (Ra). In the models presented, the supergenic processes configurate the slopes in the eluvial, transeluvial, superaqual and aqual landscapes, this last one not considered in this study. Each of these landscapes is characterized by different geoforms, types and thickness of the residual soils and their permea-porosities, and associated to different radionuclides U and Th (Ra) concentrations and their respective hosting phases, as well as different water regimens of the phreatic aquifer (figure 2). The eluvial landscape is the place where Latosols mostly occur. In this case, the main U and Th (Ra) anomalies are located on the top of latosolic B horizon, and they are due to the relative accumulation of resistate minerals, insoluble Th compounds, and U and Th fixed to Fe and Al oxihydroxides and clays by adsorption. In this landscape, the aeration zone of the aquifer presents its maximum thickness, and the groundwater flows are vertical downward. In the transeluvial landscape, the dominant soils are the Podzolic, originated from the podzolization of the pre-existant Latosols. Moreover, the Latosol-Podzolic transformation system comprises a second generation of radioanomalies, more intense and with higher proportions of adsorbed U, and resultant from the reworking of the anomalies associated with the Latosols. Such a transforming phase is also responsible for the change in the existant versant slope angle and “permea-porosities”, forming a perched sub-system phreatic aquifer in this landscape (figure 2). The main concentrations of U and Th (Ra) are partly relative and partly absolute, and are located on the top of textural B horizon of the Podzoloic Soils, in hosting phases similar to the ones from the previous landscape, and containing organic matter as well. The groundwater flows are essentially lateral, the most superficial ones canalized through the A and E pedologic horizons of the perched sub-system aquifer. In the superaqual landscape, the radioanomalies are primarily uraniferous and absolute in nature, with U adsorbed to clays, organic matter and oxides of A0 and A1 horizons of the Hydromorphic Soils (figure 2), the migration of uraniferous solutions occurring in two principal phases. The first one, longer and older than 1 My, took place during latolization. The second phase, younger and affecting more limited geographic areas, occurred during the Latosols podzolization, between 100,000 and 500,000 years, having part of the solutions drained into the current drainage system. In this landscape, the groundwater flows are predominantly lateral during the rainy seasons, and vertical upward during dry seasons. Hence, the supergenic alteration products, organized on a slope system, are materials in which the rates of radon exhalation are higher than the ones measured on unaffected subjacent rock. Based on the secondary concentrations and hosting phases of U and Th (Ra), on the “permea-porosities” of the soils and their spatial relationships with the phreatic system, and considering the soil moisture content near the field capacity, the higher rates of Rn exhalation, mainly 222 Rn, are likely to happen in Hydromorphic Soils in the superaqual landscape and in Podzolic Soils in transeluvial landscape (table 1 and 2 and figure 2). This Rn exhalation rates are conditioned by a positive combination between Rn generation and emanation. Exceptions occur in areas under the influence of the current drainage system of the superaqual landscape, where 238 U younger than 1 My is in radioactive disequilibrium with their daughters, which causes a negative impact on Rn generation. In the eluvial landscape, despite the existance of high content of U and Th (Ra) associated with the Latosols, due to the accumulation of resistates with U and Th, Th compounds, and U and Th adsorbed in oxihydroxides and clays, the Rn fluxes are less important, and are controlled by the low emanation of most of the hosting phases mentioned (table 1). It is important to note that other soil moisture contents may affect the intensities of Rn fluxes significantly (table 2). At last the approach which has been used has led to an evaluation of Rn exhalation conditioning factors while referring to humid tropical landscapes. All kinds of parameters, climatic, geochemical, weathering, pedogenetic, morphogenetic and hydrogeologic parameters could be integrated into the scale of elementary landscape slope, and they all can be integrated among themselves and also to the radioactive processes of Rn generation, emanation, migration and exhalation, by means of an interdisciplinary, tridimensional and systemic viewpoint. U, Th, Ra and Rn behaviors have been fully investigated, making it possible to establish previsional models of Rn exhalation in scales compatible to dimensions of small habitational nuclei or even unitary dwellings.
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Andajani, Rezkia Dewi, Takeshi Tsuji, Roel Snieder, and Tatsunori Ikeda. "Spatial and temporal influence of rainfall on crustal pore pressure based on seismic velocity monitoring." Earth, Planets and Space 72, no. 1 (2020). http://dx.doi.org/10.1186/s40623-020-01311-1.
Full textAbstract:
AbstractCrustal pore pressure, which controls the activities of earthquakes and volcanoes, varies in response to rainfall. The status of pore pressure can be inferred from observed changes in seismic velocity. In this study, we investigate the response of crustal pore pressure to rainfall in southwestern Japan based on time series of seismic velocity derived from ambient noise seismic interferometry. To consider the heterogeneity of the area, rainfall and seismic velocity obtained at each location were directly compared. We used a band-pass filter to distinguish the rainfall variability from sea level and atmospheric pressure, and then calculated the cross-correlation between rainfall and variations in S-wave velocity (Vs). A mostly negative correlation between rainfall and Vs changes indicates groundwater recharge by rainfall, which increases pore pressure. The correlations differ between locations, where most of the observation stations with clear negative cross-correlations were located in areas of granite. On the other hand, we could not observe clear correlations in steep mountain areas, possibly because water flows through river without percolation. This finding suggests that geographical features contribute to the imprint of rainfall on deep formation pore pressure. We further modelled pore pressure change due to rainfall based on diffusion mechanism. A strong negative correlation between pore pressure estimated from rainfall and Vs indicates that the Vs variations are triggered by pore pressure diffusion in the deep formation. Our modelling results show a spatial variation of diffusion parameter which controls the pore pressure in deep formation. By linking the variations in seismic velocity and crustal pore pressure spatially, this study shows that seismic monitoring may be useful in evaluating earthquake triggering processes or volcanic activity.