Evaluation of silica-water surface chemistry using NMR spectroscopy     

Susan A. Carroll  Robert S. MaxwellWilliam Bourcier  Sue MartinSuzy Hulsey 《Geochimica et cosmochimica acta》2002,66(6):913-926

We have combined traditional batch and flow-through dissolution experiments, multinuclear nuclear magnetic resonance (NMR) spectroscopy, and surface complexation modeling to re-evaluate amorphous silica reactivity as a function of solution pH and reaction affinity in NaCl and CsCl solutions. The NMR data suggest that changes in surface speciation are driven by solution pH and to a lesser extent alkali concentrations, and not by reaction time or saturation state. The ²⁹Si cross-polarization NMR results show that the concentration of silanol surface complexes decreases with increasing pH, suggesting that silanol sites polymerize to form siloxane bonds with increasing pH. Increases in silica surface charge are offset by sorption of alkali cations to ionized sites with increasing pH. It is the increase in these ionized sites that appears to control silica polymorph dissolution rates as a function of pH. The ²³Na and ¹³³Cs NMR results show that the alkali cations form outersphere surface complexes and that the concentration of these complexes increases with increasing pH. Changes in surface chemistry cannot explain decreases in dissolution rates as amorphous silica saturation is approached. We find no evidence for repolymerization of the silanol surface complexes to siloxane complexes at longer reaction times and constant pH.  相似文献   

Quantification of strain rate in the Western Alps using geodesy: comparisons with seismotectonics   总被引：1，自引：0，他引：1  

Bastien Delacou  Christian Sue  Jean-Mathieu Nocquet  Jean-Daniel Champagnac  Cécile Allanic  Martin Burkhard 《Swiss Journal of Geoscience》2008,101(2):377-385

The contrasted seismotectonic regime of the Western Alps is characterized by radial extension in the high chain, combined with local compressive areas at the foothill of the belt, and everywhere occurrence of transcurrent tectonics. Here, we compare this seismotectonic regime to a large-scale compilation of GPS measurements in the Western Alpine realm. Our analysis is based on the raw GPS database, which give the measured velocity field with respect to the so called “stable Europe”, and an interpolated velocity field, in order to smooth the database on a more regular mesh. Both strain rate and rotational components of the deformation are investigated. The strain rate field shows patch-like structure, with extensional areas located in the core and to the North of the belt and compressional areas located in its periphery. Although the GPS deformation fields (both raw and interpolated) are more spatially variable than the seismotectonic field, a good qualitative correlation is established with the seismotectonic regionalization of the deformation. The rotation rate fields (both raw and interpolated) present counterclockwise rotations in the innermost part of the belt and a surprising continuous zone of clockwise rotations following the arc-shape geometry of the Western Alps along their external border. We interpret this new result in term of a counterclockwise rotation of the Apulia plate with respect to the stable Europe. This tectonic scheme may induce clockwise rotations of crustal block along the large strike-slip fault system, which runs in the outer part of the belt, from the Rhône-Simplon fault to the Belledonne fault and Southeastward, to the High-Durance and Argentera fault.  相似文献   

The kinetic interactions of metal ions with humic acids     

Gregory R. Choppin  Sue B. Clark   《Marine Chemistry》1991,36(1-4)

Complexation of europium (III) and UO₂²⁺ by humic acid was found to be very fast (< 1 m). However, passage through ion exchange resin removed a fraction which decreased as the contact time increased over a 2–3 day period. The dissociation kinetics for UO₂²⁺-humate were described by an equation with five first order terms with rate constants ranging from 40.6 m⁻¹ to 5.64×10⁻³ m⁻¹. The percentage of UO₂²⁺ dissociating by the slower paths, comparable to that eluting with the humic acid through the ion exchange resin is assigned to internal site-bound cations (strong binding). The faster dissociating fraction corresponded roughly to the UO₂²⁺ removed by the cation exchange resin (weak binding). The time dependence of the weak to strong binding ratio was associated with change in the conformation of the macromolecular humic acid as the cations neutralized the charge repulsions of the anionic humate.  相似文献   

Experiments with Rhodamine B and European Flat Oysters (Ostrea edulis L)     

Waugh  G. Duncan; Key  D. 《ICES Journal of Marine Science》1967,31(2):272-278

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Zur Deutung der Vertikalbewegungen der Festländer und Meere     

Franz E. Sueß 《International Journal of Earth Sciences》1920,11(1-4):144-168

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Assessing the health effects of climate change in Alaska with community-based surveillance     

David L. Driscoll  Erica Mitchell  Rebecca Barker  Janet M. Johnston  Sue Renes 《Climatic change》2016,137(3-4):455-466

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Geology of the platanares geothermal area, Departamento de Copán, Honduras     

Grant Heiken  Napoleon Ramos  Wendell Duffield  John Musgrave  Kenneth Wohletz  Sue Priest  James Aldrich  Wilmer Flores  Alexander Ritchie  Fraser Goff  Dean Eppler  Carlos Escobar 《Journal of Volcanology and Geothermal Research》1991,45(1-2)

The Platanares geothermal area, Departamento de Copán, Honduras, is located within a graben that is complexly faulted. The graben is bounded on the north by a highland composed of Paleozoic (?) metamorphic rocks in contact with Cretaceous - Tertiary redbeds of unknown thickness. These are unconformably overlain by Tertiary andesitic lavas, rhyolitic ignimbrites, and associated sedimentary rocks. The volcanic rocks are mostly older than 14 Ma, and thus are too old to represent the surface expression of an active crustal magma body. Thermal fluids that discharge in the area are heated during deep circulation of meteoric water along faults in a region of somewhat elevated heat flow. Geothermometry based upon the chemical composition of thermal fluids from hot springs and from geothermal gradient coreholes suggests that the reservoir equilibrated at temperatures as high as 225 to 240°C, within the Cretaceous redbed sequence. Three continuously cored geothermal gradient holes have been drilled; fluids of about 165°C have been produced from two drilled along a NW-trending fault zone, from depths of 250 to 680 m. A conductive thermal gradient of 139°C/km, at a depth of 400 m, was determined from the third well, drilled 0.6 km west of that fault zone. These data indicate that the Platanares geothermal area holds considerable promise for electrical generation by moderate- to hightemperature geothermal fluids.  相似文献   

Enhancing the human benefits of flood warnings     

Dennis Parker  Sue Tapsell  Simon McCarthy 《Natural Hazards》2007,43(3):397-414

This article evaluates some of the factors which limit the human benefits of hazard warnings, with specific reference to flood warnings, and we conclude by suggesting ways of enhancing these benefits. We focus mainly upon the economic benefits generated by flood damage savings by households that warnings facilitate; health effects of flooding and flood warnings; and the effects of warnings on loss of life and physical injury. Our results, based partly upon surveys of flooded households, reveal that economic benefits are currently more limited than we previously thought, but that for several reasons these benefits are likely to be under-estimated. We argue that the intangible benefits to public health, safety and security must also be taken into account in decisions about investment in flood warnings. In England and Wales, the public’s response to flood warnings is currently low and is a key benefit-limiting factor which could begin to undermine a recent major shift in national flood risk management policy towards a more people-centred, portfolio approach in which changing human behaviour is viewed as important. Using a trans-disciplinary approach, we discuss the evidence and literature surrounding this poor response, and suggest a number of ways in which the issue may be addressed in future.  相似文献   

Local tomography and focal mechanisms in the south-western Alps: Comparison of methods and tectonic implications     

Bthoux Nicole  Sue Christian  Paul Anne  Virieux Jean  Frchet Julien  Thouvenot Franois  Cattaneo Marco 《Tectonophysics》2007,432(1-4):1-19

We investigate how focal solutions and hypocenter locations may depend on the ray tracing algorithm and the strategy of velocity inversion. Using arrival times from a temporary seismological network in the south-western Alps, a local earthquake tomography has been performed by Paul et al. [Paul, A., Cattaneo, M., Thouvenot, F., Spallarossa, D., Béthoux, N., and Fréchet, J., 2001. A three-dimensional crustal velocity model of the south-western Alps from local earthquake tomography. J. Geophys. Res. 106, 19367–19390.] with the method developed by Thurber [Thurber, C.H., 1993. Local earthquake tomography: velocity and Vp/Vs-Theory, in Seismic Tomography: Theory and practice, Iyer, H.M., and Irahara eds., Chapman and Hall, New York, 563–583.]. Another inversion of the same data set is performed here using a different tomography code relying on a shooting paraxial method and cubic interpolation of velocities. The resulting images display the same main features, although Thurber's code appears to be more robust in regions with scarce ray coverage and strong velocity contrasts. Concerning hypocenter location in Piemont units, one major result is the concentration of hypocenters at the boundary between the mantle wedge of the Ivrea body and the European crust. Forty-six focal mechanisms are shown that were computed using both the take-off angles in the minimum 1-D model and in the 3-D velocity structures resulting from the two inversions. The sets of focal solutions are very similar, proving the reliability and the coherency of the focal solutions. The widespread extension in the core of the western Alps is confirmed whereas a few compressive solutions are found east of the Piemont units. These results constrain the sharp change of stress tensor and evidence a decoupling of strain beneath the east of Dora Maira massif up to beneath the north of Argentera massif. On a geodynamical point of view seismicity and focal mechanism distribution are compatible with the present day models published for the western Alps, where the major feature is the lithospheric thickening [Schmid, S.M., and Kissling, E., 2000. The arc of the western Alps in the light of geophysical data on deep crustal structure. Tectonics, 19, 62–85.], implying widespread extension in the core of the western Alps [Sue, C., Thouvenot, F., Fréchet, J., and Tricart, P., 1999. Widespread extension in the core of the western Alps revealed by earthquake analysis. J. Geophys. Res., 104, 25611–25622.]. However the existence of compressive events dealing at depth with the boundary of Ivrea body allows to postulate that this geological structure is still tectonically active. Even if field work has not shown this so far, the Insubric line appears to extend toward the south at depth, as a blind fault, and to play a key role in the dynamics of the south-western Alps.  相似文献   

Controls on accumulation of a volcaniclastic fan,Ruapehu composite volcano,New Zealand     

Beth A Palmer  Andrew M Purves  Sue L Donoghue 《Bulletin of Volcanology》1993,55(3):176-189

The Whangaehu fan is the youngest sedimentary component on the eastern ring plain surrounding Ruapehu volcano. Fan history comprises constructional (830–200 years bp) and dissectional (<200 years bp) phases. The constructional phase includes four aggradational periods associated with both syneruptive and inter-eruptive behavior. All four aggradational periods began when deposition by large lahars changed flow conditions on the fan from channelized to unchannelized. Subsequent behavior was a function of the rate of sediment influx to the fan. The rate of sediment influx, in turn, was controlled by frequency and magnitude of volcanic eruptions, short-term climate change, and the amount of sediment stored on the volcano flanks. Fanwide aggradation occurred when rates of sediment influx and deposition on the fan were high enough to maintaìn unchannelized flow conditions on the fan surface. Maintenance of an undissected surface required sedimentation from frequent and large lahars that prevented major dissection between events. These conditions were best met during major eruptive episodes when high frequency and magnitude eruptions blanketed the volcano flanks with tephra and rates of lahar initiation were high. During major eruptive episodes, volcanism is the primary control on sedimentation. Climatic variations do not influence sediment accumulation. Local aggradation occurred when lahars were too small to maintain unchannelized flow across the entire fan. In this case, only the major channel system received much sediment following the deposition from the initial lahar. This localized aggradation occurred if (1) the sediment reservoir on the flank was large enough for floods to bulk into debris flows and (2) sedimentation events were frequent enough to maintain sediment supply to only some parts of the fan. These conditions were met during both minor eruptive and inter-eruptive episodes. In both cases, a large sediment reservoir remained on the volcano flanks from previous major eruptive intervals. Periods of increased storm activity produced floods that bulked to relatively small debris flows. When the sediment reservoir was depleted, the fan entered the present dissectional phase. Syneruptive and noneruptive lahars are mostly channelized and sediment bypasses the fan. Fan deposits are rapidly reworked. This is the present case at Ruapehu, even though the volcano is in a minor eruptive episode and the climate favors generation of intense storm floods.  相似文献