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61.
62.
Dr. Alfons Zehnder 《Aquatic Sciences - Research Across Boundaries》1963,25(1):65-83
Ohne Zusammenfassung
Publikation NRC Nr. 7225. 相似文献
63.
Raphael Schneeberger Daniel Egli Georg W. Lanyon Urs K. Mäder Alfons Berger Florian Kober Marco Herwegh 《Hydrogeology Journal》2018,26(8):2725-2738
Groundwater flow in granitic bedrock is of major interest for underground projects such as radioactive waste disposal. It is generally accepted that granitic rocks of the upper crust are characterized as faulted low-porosity rocks showing fault-related permeability. In this study, the influence of existing faults on the present-day water flow in the Grimsel Test Site (Switzerland), an underground rock laboratory situated in granitoid rocks, was investigated by mapping water discharges. As a result, the link between water flow and faults considering slip-tendency analysis and fault intersections is evaluated. Water-conducting features were combined in a structural-permeability favorability map. Faults and dykes occur as three orientation groups, NE–SW, E–W, and NW–SE trending, all steeply dipping southwards with fault intersections also steeply plunging southwards. In total, 100 water discharges were mapped in summer 2014 and 85 in winter 2016, which are located along faults or fault intersections. A comparison of water discharges with structures showed that high-slip-tendency metabasic dykes and fault or dyke intersections represent the dominant flow paths. Further, it could be demonstrated that higher slip-tendency tends to lead to enhanced average hydraulic conductivity and therefore more constant water flow. Based on water fluxes, fault intersections are inferred to represent first-order locations of water percolation followed by high-slip-tendency metabasic dykes. The combination of all water-conducting features into a structural-permeability map results in covering all water discharges. Therefore, the structural-permeability favorability map can serve as suitable representation for constraining water inflow in fractured granitoid host rocks. 相似文献
64.
Marianne Negrini Holger Stunitz Alfons Berger Luiz F. G. Morales 《Contributions to Mineralogy and Petrology》2014,167(3):1-22
We performed high strain (up to 47 %) axial compression experiments on natural quartz single crystals with added rutile powder (TiO2) and ~0.2 wt% H2O to investigate the effects of deformation on the titanium-in-quartz (TitaniQ) geothermobarometer. One of the objectives was to study the relationships between different deformation mechanisms and incorporation of Ti into recrystallized quartz grains. Experiments were performed in a Griggs-type solid-medium deformation apparatus at confining pressures of 1.0–1.5 GPa and temperatures of 800–1,000 °C, at constant strain rates of 1 × 10?6 or 1 × 10?7 s?1. Mobility of Ti in the fluid phase and saturation of rutile at grain boundaries during the deformation experiments are indicated by precipitation of secondary rutile in cracks and along the grain boundaries of newly recrystallized quartz grains. Microstructural analysis by light and scanning electron microscopy (the latter including electron backscatter diffraction mapping of grain misorientations) shows that the strongly deformed quartz single crystals contain a wide variety of deformation microstructures and shows evidence for subgrain rotation (SGR) and grain boundary migration recrystallization (GBMR). In addition, substantial grain growth occurred in annealing experiments after deformation. The GBMR and grain growth are evidence of moving grain boundaries, a microstructure favored by high temperatures. Electron microprobe analysis shows no significant increase in Ti content in recrystallized quartz grains formed by SGR or by GBMR, nor in grains grown by annealing. This result indicates that neither SGR nor moving grain boundaries during GBMR and grain growth are adequate processes to facilitate re-equilibration of the Ti content in experimentally deformed quartz crystals at the investigated conditions. More generally, our results suggest that exchange of Ti in quartz at low H2O contents (which may be realistic for natural deformation conditions) is still not fully understood. Thus, the application of the TitaniQ geothermobarometer to deformed metamorphic rocks at low fluid contents may not be as straightforward as previously thought and requires further research. 相似文献
65.
Spatial and temporal variations of pCO2, dissolved inorganic carbon and stable isotopes along a temperate karstic watercourse
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Robert van Geldern Peter Schulte Michael Mader Alfons Baier Johannes A. C. Barth 《水文研究》2015,29(15):3423-3440
This study investigated CO2 degassing and related carbon isotope fractionation effects in the Wiesent River that drains a catchment in the karst terrain of the Franconian Alb, Southern Germany. The river was investigated by physico‐chemical and stable isotope analyses of water and dissolved inorganic carbon during all seasons along 65‐km long downstream transects between source and mouth. Calculated pCO2 values at the source were 21 400 ± 2400 µatm. The pCO2 rapidly decreased in the river water and dropped to an average of 1240 ± 330 µatm near the mouth. About 90% of this decrease occurred within the first 6 km of the river. The river was supersaturated with respect to CO2 over its entire course and must have acted as a continuous year‐round CO2 source to the atmosphere. The average CO2 flux from the karst river was estimated with 450 mmol m?2 day?1 with higher fluxes up to 5680 mmol m?2 day?1 at the source. At the source, δ13CDIC values showed no seasonal variations with an average of ?14.2 ± 0.2‰. This indicated that groundwater retained high pCO2 mainly from soil CO2. The contribution of soil CO2 to dissolved inorganic carbon was estimated at 65% to 72%. The downstream CO2 loss caused a positive shift in δ13CDIC values of 2‰ between source and mouth because of the preferential loss of the 12C isotope during degassing. Considering the findings of this study and the fact that carbonate lithology covers a significant part of the earth's surface, CO2 evasion from karst regions might contribute notably to the annual carbon dioxide release from global freshwater systems. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
66.
67.
Dr. Alfons Zehnder 《Aquatic Sciences - Research Across Boundaries》1977,39(2):114-151
Ohne Zusammenfassung
Internationale Arbeitsgemeinschaft für Cyanophytenforschung IAC 相似文献
68.
Alfons Zehnder 《Aquatic Sciences - Research Across Boundaries》1964,26(1):147-164
Ohne Zusammenfassung 相似文献
69.
Alfons Zehnder Dr. J. Komárek Prof. Dr. S. Golubić Prof. Dr. R. Y. Stanier Dr. J. Komárek Dr. J. Ludvík Dr. L. Kováčik Dr. Asta Almestrand Prof. Dr. P. Compère Dr. D. Mollenhauer Dr. F. Hindák Dr. T. P. Chang Dr. Nagaraj Jeeji Bai C. V. Seshadri Dr. M. -E. Meffert Dr. R. Oberhäuser Dr. J. Overbeck Dr. F. Hindák Susan E. Campbell Dr. Jaroslava Komárková Dr. U. Uehlinger Dr. F. Schanz Dr. Alfons Zehnder 《Aquatic Sciences - Research Across Boundaries》1983,45(1):267-310
The 8th Symposium of the International Association for Cyanophyte Research IAC was attended by 29 specialists from 11 countries.
The 19 oral presentations and discussions centered on the following themes: The basic principles of cyanophyte taxonomy (3
lectures), systematic problems of certain taxonomic groups (5 lectures), morphology (6 lectures) and ecology (5 lectures).
The intensive discussions between representatives of the classical (european) taxonomic treatment of cyanophytes (based on
morphological and ecological characteristics) and those representing the bacteriological study of ‘cyanobacteria’ were especially
valuable. The central theme of the meeting was, however, the mutual microscopic study and discussion of problematic blue-greens
from natural habitats, that were mostly collected during the three field trips into different areas of central Switzerland
(Grimsel-Gotthard-Nufenen. Klewenalp. Gerzensee).
相似文献
70.