A Poroelastic Description of Permeability Evolution     

Alireza Hassanzadegan  Günter Zimmermann 《Pure and Applied Geophysics》2014,171(7):1187-1201

Pore pressure changes in a geothermal reservoir, as a result of injection and/or production of water, result in changes of stress acting on the reservoir rock and, consequently, changes in the mechanical and transport properties of the rock. Bulk modulus and permeability were measured at different pressures and temperatures. An outcropping equivalent of Rotliegend reservoir rock in the North German Basin (Flechtinger sandstone) was used to perform hydrostatic tests and steady state fluid flow tests. Permeability measurements were conducted while cycling confining pressure; the dependence of permeability on stress was determined at a constant downstream pressure of 1 MPa. Also, temperature was increased stepwise from 30 to 140 °C and crack porosity was calculated at different temperatures. Although changes in the volumes of cracks are not significant, the cracks control fluid flow pathways and, consequently, the permeability of the rock. A new model was derived which relates microstructure of porosity, the stress–strain curve, and permeability. Porosity change was described by the first derivative of the stress–strain curve. Permeability evolution was ascribed to crack closure and was related to the second derivative of the stress–strain curve. The porosity and permeability of Flechtinger sandstone were reduced by increasing the effective pressure and decreased after each pressure cycle.  相似文献   

Postulated responses of phytoplankton and bacteria to predicted increases of inorganic suspended sediments in oligotrophic lakes     

Marc Schallenberg  Udo Friedrich  Carolyn W. Burns 《新西兰海洋与淡水研究杂志》2013,47(4):763-779

We establish the relationships between concentrations of inorganic suspended sediments (ISS) on light, nutrients, phytoplankton, and bacteria in three oligotrophic lakes (four sites) and we use these relationships to predict the impacts of increasing concentrations of ISS on the biomass and productivity of phytoplankton and bacteria in the lakes. Increased concentrations of ISS contributed little available nutrient to the lakes. The relationships between ISS and underwater light attenuation differed among lakes because of variation in sediment size‐structure, and composition. Only at the site with the highest ISS concentrations and a relatively deep mixing depth, were phytoplankton apparently light‐limited and, thus, predicted to decline with increased ISS concentrations. In contrast to previously published studies, bacterial abundance and production were not highly correlated to suspended sediment concentrations in these lakes. However, bacterial biomass, productivity, and specific productivity were more strongly correlated to phytoplankton production. As a result of light limitation and stimulation of bacterial production, increases in ISS concentrations are not predicted to significantly shift the metabolic balance in the planktonic ecosystem of three of the sites towards greater heterotrophy. Where light limits phytoplankton production, increases in ISS are predicted to reduce the productivity of both phytoplankton and bacteria by direct inhibition of phytoplankton production, again without a large shift towards greater importance of the microbial loop. By reducing phytoplankton production and inhibiting larger cladoceran grazers, we predict that high concentrations of ISS will reduce available energy and its flow up the food chain.  相似文献   

Laser Ablation (193 nm), Purification and Determination of Very Low Concentrations of Solar Wind Nitrogen Implanted in Targets from the GENESIS Spacecraft     

Laurent Zimmermann  Pete Burnard  Bernard Marty  Fabien Gaboriaud 《Geostandards and Geoanalytical Research》2009,33(2):183-194

The GENESIS space mission recovered ions emitted by the Sun during a 27 month period. In order to extract, purify and determine the very low quantities of solar nitrogen implanted in the GENESIS targets, a new installation was developed and constructed at the CRPG (Nancy, France). It permitted the simultaneous determination of nitrogen and noble gases extracted from the target by laser ablation. The extraction procedure used a 193 nm excimer laser that allowed for surface contamination in the outer 5 nm to be removed, followed by a step that removed 50 nm of the target material, extracting the solar nitrogen and noble gases implanted in the target. Following purification using Ti and Zr getters for noble gases and a Cu-CuO oxidation cycle for N₂, the extracted gases were analysed by static mode (pumps closed) mass spectrometry using electron multiplier and Faraday cup detectors. The nitrogen blanks from the purification section and the static line (30 minutes) were only 0.46 picomole and 0.47 picomole, respectively.  相似文献   

Implications of tree species–environment relationships for the responsiveness of Himalayan krummholz treelines to climate change     

Niels Schwab  Udo Schickhoff  Birgit Bürzle  Michael Müller  Jürgen Böhner  Ram Prasad Chaudhary  Thomas Scholten  Jens Oldeland 《山地科学学报》2017,14(3):453-473

Climate warming is expected to advance treelines to higher elevations. However, empirical studies in diverse mountain ranges give evidence of both advancing alpine treelines as well as rather insignificant responses. In this context, we aim at investigating the sensitivity and responsiveness of the near-natural treeline ecotone in Rolwaling Himal, Nepal, to climate warming. We analysed population densities of tree species along the treeline ecotone from closed forest stands via the krummholz belt to alpine dwarf shrub heaths (3700-4200 m) at 50 plots in 2013 and 2014. We quantified species - environment relationships, i.e. the change of environmental conditions (e.g., nutrient and thermal deficits, plant interactions) across the ecotone by means of redundancy analyses, variation partitioning and distance-based Moran's eigenvector maps. In particular, we focus on explaining the high competitiveness of Rhododendron campanulatum forming a dense krummholz belt and on the implications for the responsiveness of Himalayan krummholz treelines to climate change. Results indicate that treeline trees in the ecotone show species-specific responses to the influence of environmental parameters, and that juvenile and adult tree responses are modulated by environmental constraints in differing intensity. Moreover, the species - environment relationships suggest that the investigated krummholz belt will largely prevent the upward migration of other tree species and thus constrain the future response of Himalayan krummholz treelines to climate warming.  相似文献   

FTIR micro-reflectance measurements of the CO3 2– ion content in basanite and leucitite glasses     

A. Grzechnik  Hans D. Zimmermann  P. L. King  Paul F. McMillan  R. L. Hervig 《Contributions to Mineralogy and Petrology》1996,125(4):311-318

 Infrared spectroscopy provides a reliable method for rapid, non-destructive quantitative analysis of volatile species in silicate glasses, with applications to geochemistry and volcanology. The technique has been extensively calibrated for transmission measurements, in which the species concentration present is correlated with the height or area of characteristic absorption peaks, for doubly polished samples of known thickness. There are several drawbacks associated with this method, including the need for double polishing of parallel faces on thin samples, the errors associated with sample thickness measurement, and total absorption of the IR beam intensity for samples with high volatile content. We have tested an alternative method for quantitative IR determination of volatile concentrations in silicate glasses, based on analysis of the IR reflectivity signal. The reflectivity method requires preparation of a single polished glass surface, and no thickness measurement of the sample is necessary. The technique is applied easily as a microbeam technique using apertures as small as a few μm in diameter. The method should be particularly useful for volatile analysis of glass inclusions in phenocrystals, or standard samples in thin section. We have developed the methodology for the technique using a series of basanite and leucitite glasses with high carbonate contents (>1 wt% CO₂), which could not be easily analyzed via IR transmission. We have used SIMS to standardize the technique. Two features observed in the reflectance spectra near 1400 cm^–1 and 1500 cm^–1 are due to resonance of the infrared beam with the asymmetric stretching vibrations of carbonate groups. The contribution of these species to the total reflectivity is directly correlated with the carbon abundance in the samples. This forms the basis for an empirical quantitative analysis. The optical constants, including the IR absorption coefficients associated with the CO₃ ^2– stretching vibrations, have been extracted by Kramers-Kronig analysis of the reflectivity data. The molar extinction coefficients are 1119 ± 138 L mol^–1 cm^–1 and 1198 ± 145 L mol^–1 cm^–1 for the 1400 and 1500 cm^–1 bands, respectively, in excellent agreement with results of previous transmission studies, after orientation effects are taken into account. Received: 29 September 1995 / Accepted: 17 May 1996  相似文献   

Etude de la phase gazeuse occluse dans les laves de «l’Ardoukôba», volcan éphémère d’une dorsale émergée (Afar)     

J. L. Zimmermann  J. L. Cheminee  M. Chaigneau 《Bulletin of Volcanology》1981,44(3):527-546

Gases trapped in lavas of three main flows of the Ardoukôba eruption (8 to 15 November, 1978) have been analysed by mass spectrometry. These analyses concern both plagioclase phenocrysts and microcrystalline mesostasis. Fluids are released between 500°C and 1200°C, and consist of H₂O, CO₂, CO, N₂, SO₂, HCl, H₂, CH₄ with traces of hydrocarbons and H₂S. The total content is less than 0.3–0.4 wt. % of samples with about 0.1–0.15 wt % of H₂O. No significant variation among the three flows is observed. Plagioclase phenocrysts are less abundant in fluids than the mesostasis (～2/3). The gases trapped in these phenocrysts are richer in CO and organic compounds, whereas mesostasis contain more H₂O, CO₂ and SO₂. CO is likely produced by reduction of CO₂ and H₂O with carbon during either analyses or eruption itself, or is of primary origin. In the latter case, gas composition suggests an entrapment temperature of about 1200°C ± 75°C. Kinetic study of the water and carbon dioxide release allows to calculate the diffusion characteristics of these fluids. Water and carbon dioxide behave rather similarly. Plagioclase gives a single activation energy value (8 Kcal/mole), while mesostasis gives two values (8 Kcal/mole, 15 Kcal/mole). Diffusion coefficients at 20°C are estimated to fall in the range 10^?13 · 10^?12 cm² · sec^?1.  相似文献   

Ein Zusammenhang zwischen der Fällung von Wismutoxychlorid (anorganischer Test von Piccardi) und der Sonnentätigkeit     

Udo Becker 《Theoretical and Applied Climatology》1955,6(4):511-516

Zusammenfassung Es wird nachgewiesen, daß die Fällungsgeschwindigkeit von Wismutoxychlorid in sehr engem Zusammenhang steht mit der Sonnenfleckentätigkeit (Korrelationskoeffizient etwa 0,9). Ferner zeigen die Werte der nicht durch einen Faradaykäfig abgeschirmten Fällungen nach chromosphärischen Eruptionen einen Anstieg von mehr als 20%.

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Summary The author proves that the rate of precipitation of bismuth oxychloride shows a very narrow relation with the sunspot activity (correlation coefficient ca. 0,9). Furthermore those precipitations which are not separated by a Farady cage show an ascent of more than 20% after chromospheric eruptions.

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Résumé L'auteur démontre dans ce travail que la vitesse de précipitation du chlorure de bismuth est en rapport très étroit avec l'activité des taches solaires (coefficient de corrélation environ 0,9). D'autre part les précipitations qui ne sont pas isolées au moyen d'une cage de Faraday, indiquent une augmentation de vitesse de plus de 20% après des éruptions chromosphériques.

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Mit 6 Textabbildungen.  相似文献   

Über die Entnahme von Wasserproben in fliessenden Gewässern     

O. Jaag  H. Ambühl  P. Zimmermann 《Aquatic Sciences - Research Across Boundaries》1956,18(1):156-160

Ohne Zusammenfassung  相似文献   

Fission track age of Stibiotantalite from Alto Ligonha,Mozambique     

Dr. Udo Haack 《Contributions to Mineralogy and Petrology》1970,29(2):183-185

Fossil fission tracks in a stibiotantalite were revealed by etching and used for fission track dating. The fission track age of this specimen (2.3·10⁸ yr.) is much lower than Pb/Pb and Rb/Sr ages of other minerals from the same area. The explanation for this discrepancy could be the only moderate track retentivity of stibiotantalite which is similiar to muscovite.  相似文献   

Zur Methodik der Quantitativen Biologischen Probenahmen in Stark Strömenden Flüssen     

Dr. U. Von Zimmermann  Dr. H. Ambühl 《Aquatic Sciences - Research Across Boundaries》1970,32(1):340-344

Zusammenfassung Es wird eine Technik zur Entnahme quantitativer Organismenproben aus tiefen, schnellfliessenden, steinigen Flüssen beschrieben. Mit Hilfe eines kreisrunden Stechsegmentes wird ein Areal von rund 750 cm² abgegrenzt und dieses sodann mit einem Vakuumschlauch abgesaugt. Das Mundstück des Schlauches wird durch einen Taucher geführt.

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Summary A technique is described for taking quantitative samples of organisms from deep, rapidly flowing rivers with rocky beds. An area of about 750 cm² (0.81 sqft) is confined by a circular sampler, which penetrates the bottom. Organisms in the enclosure are freed from the substrate by hand. Smaller sediment particles, organisms, and water are then pumped out by a vacuum hose. The intake of the vacuum hose is guided by a diver.

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