Combined tracer tests in the karst aquifer of the artesian mineral springs of Stuttgart,Germany   总被引：3，自引：0，他引：3  

N. Goldscheider  H. Hötzl  W. Käss  W. Ufrecht 《Environmental Geology》2003,43(8):922-929

Chlorinated solvents have been detected at low concentrations in some of the mineral and medicinal springs (spas) of Stuttgart since 1984. These springs discharge from a confined karst aquifer. In order to investigate both the properties of the aquifer and the mechanisms of contaminant transport, two multi-tracer tests were carried out in 1998 and 1999. Both fluorescent tracers (naphthionate, eosin, pyranine) and particle tracers (clubmoss spores, microspheres) were used. All available wells and springs were sampled for at least 12 months. In these experiments naphthionate produced the best results. Maximum flow velocities were established to be within the range of 53 and 230 m/day. The breakthrough curves demonstrated a heterogeneous aquifer. The results identified flow to the springs from the west and south-west. It was possible to prove an assumed boundary between the northern zone of low mineralised water and the southern zone of highly mineralised water.  相似文献   

On the role of subducting oceanic plateaus in the development of shallow flat subduction   总被引：2，自引：0，他引：2  

Jeroen van Hunen  Arie P. van den Berg  Nico J. Vlaar 《Tectonophysics》2002,352(3-4)

Oceanic plateaus, aseismic ridges or seamount chains all have a thickened crust and their subduction has been proposed as a possible mechanism to explain the occurrence of flat subduction and related absence of arc magmatism below Peru, Central Chile and at the Nankai Trough (Japan). Their extra compositional buoyancy could prohibit the slab from sinking into the mantle. With a numerical thermochemical convection model, we simulated the subduction of an oceanic lithosphere that contains an oceanic crustal plateau of 18-km thickness. With a systematic variation, we examined the required physical parameters to obtain shallow flat subduction. Metastability of the basaltic crust in the eclogite stability field is of crucial importance for the slab to remain buoyant throughout the subduction process. In a 44-Ma-old subducting plate, basalt must be able to survive a temperature of 600–700 °C to keep the plate buoyant sufficiently long to cause a flat-slab segment. We found that the maximum yield stress in the slab must be limited to about 600 MPa to allow for the necessary bending to the horizontal. Young slabs show flat subduction for larger parameter ranges than old slabs, since they are less gravitationally unstable and show less resistance against bending. Hydrous weakening of the mantle wedge area and lowermost continent are required to allow for the necessary deformation of a change in subduction style from steep to flat. The maximum flat slab extent is about 300 km, which is sufficient to explain the observed shallow flat subduction near the Nankai Trough (Japan). However, additional mechanisms, such as active overthrusting by an overriding continental plate, need to be invoked to explain the flat-slab segments up to 500 km long below Peru and Central Chile.  相似文献   

A characteristics-based method for solving the transport equation and its application to the process of mantle differentiation and continental root growth     

Jeroen H. de Smet  Arie P. van den Berg  Nico J. Vlaar  & David A. Yuen 《Geophysical Journal International》2000,140(3):651-659

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Impact of managed aquifer recharge on the chemical and isotopic composition of a karst aquifer,Wala reservoir,Jordan   总被引：1，自引：1，他引：0  

Julian Xanke  Nadine Goeppert  Ali Sawarieh  Tanja Liesch  Jochen Kinger  Wasim Ali  Heinz Hötzl  Khair Hadidi  Nico Goldscheider 《Hydrogeology Journal》2015,23(5):1027-1040

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The contribution of PSInSAR interferometry to landslide hazard in weak rock-dominated areas   总被引：1，自引：0，他引：1  

S. C. Oliveira  J. L. Zêzere  J. Catalão  G. Nico 《Landslides》2015,12(4):703-719

In the Grande da Pipa river basin, north of Lisbon, 64 % of the total number of landslides inventoried is totally or partially included in a lithological unit composed by marl, clay, and sandstone intercalation complex that is present in 58 % of the study area. The Persistent Scatterer synthetic aperture radar interferometry technique is applied to a data set of TerraSAR-X SAR images, from April of 2010 to March of 2011, firstly to the Laje-Salema test site and further exported to the Grande da Pipa river basin. This work’s specific objectives are the following: (i) to assess the potential of the Persistent Scatterer displacement maps to the identification of new landslides/unstable areas and in the redefinition of landslide limits, (ii) to update the landslide state of activity, and (iii) to evaluate the capacity of the Persistent Scatterer deformation maps in assessing landslide susceptibility at the regional scale. Based on this approach, it was possible to increment the number of landslides and to redefine the landslide limits in the test site in 3.8 %. For 39 landslides, it was possible to update the landslide state of activity, in particular from dormant to reactivated or dormant-reactivated (23 landslides) or from stabilized to reactivated (5 landslides). Landslide susceptibility map based in Persistent Scatterer deformation rates, independently validated with a deep rotational slide map, obtained the best value of area under the curve (0.668).  相似文献   

Transport and Variability of Fecal Bacteria in Carbonate Conglomerate Aquifers     

Nadine Goeppert  Nico Goldscheider 《Ground water》2011,49(1):77-84

Clastic sedimentary rocks are generally considered non‐karstifiable and thus less vulnerable to pathogen contamination than karst aquifers. However, dissolution phenomena have been observed in clastic carbonate conglomerates of the Subalpine Molasse zone of the northern Alps and other regions of Europe, indicating karstification and high vulnerability, which is currently not considered for source protection zoning. Therefore, a research program was established at the Hochgrat site (Austria/Germany), as a demonstration that karst‐like characteristics, flow behavior, and high vulnerability to microbial contamination are possible in this type of aquifer. The study included geomorphologic mapping, comparative multi‐tracer tests with fluorescent dyes and bacteria‐sized fluorescent microspheres, and analyses of fecal indicator bacteria (FIB) in spring waters during different seasons. Results demonstrate that (1) flow velocities in carbonate conglomerates are similar as in typical karst aquifers, often exceeding 100 m/h; (2) microbial contaminants are rapidly transported toward springs; and (3) the magnitude and seasonal pattern of FIB variability depends on the land use in the spring catchment and its altitude. Different groundwater protection strategies that currently applied are consequently required in regions formed by karstified carbonatic clastic rocks, taking into account their high degree of heterogeneity and vulnerability.  相似文献   

First principles molecular dynamics simulations of diopside (CaMgSi₂O₆) liquid to high pressure     

Ni Sun  Nico de Koker 《Geochimica et cosmochimica acta》2011,75(13):3792-470

We use first principles molecular dynamics simulations based on density functional theory in the local density approximation to investigate CaMgSi₂O₆ liquid over the entire mantle pressure regime. We find that the liquid structure becomes much more densely packed with increasing pressure, with the mean Si-O coordination number increasing nearly linearly with volume from fourfold near ambient pressure to sixfold at the base of the mantle. Fivefold Si-O coordination environments are most abundant at intermediate compression. The properties of Mg and Si coordination environments are nearly identical to those in MgSiO₃ liquid, whereas Ca is more highly coordinated with larger mean Ca-O bond length as compared with Mg. The density increases smoothly with increasing pressure over the entire range studied. The Grüneisen parameter increases by a factor of three on twofold compression. The density contrast between diopside composition liquid and the isochemical crystalline assemblage is less than 2% at the core mantle boundary, less than that in the case of MgSiO₃. Thermodynamic properties are described in terms of a liquid-state fundamental thermodynamic relation.  相似文献   

Differential Hydrogeological Effects of Draining Tunnels Through the Northern Apennines,Italy     

Valentina Vincenzi  Alessandro Gargini  Nico Goldscheider  Leonardo Piccinini 《Rock Mechanics and Rock Engineering》2014,47(3):947-965

Water inflows are a major challenge in tunnelling and particularly difficult to predict in geological settings consisting of heterogeneous sedimentary rock formations with complex tectonic structure. For a high-speed railway line between Bologna and Florence (Italy), a series of seven railway tunnels was drilled through turbiditic formations, ranging from pelitic rocks with thin arenitic layers over sequences including thick-bedded sandstone to calcareous rocks showing chemical dissolution phenomena (karstification). The tunnels were built as draining tunnels and caused significant impacts, such as drying of springs and base-flow losses at mountain streams. A comprehensive hydrological monitoring programme and four multi-tracer test were done, focusing on four sections of the tunnel system. The tracer tests delivered unprecedented data on groundwater flow and transport in turbiditic aquifers and made it possible to better characterize the differential impacts of tunnel drainage along a geological gradient. The impact radius is 200 m in the thin-bedded sequences but reaches 2.3–4.0 km in calcareous and thick-bedded arenitic turbidites. Linear flow velocities, as determined from the peaks of the tracer breakthrough curves, range from 3.6 m/day in the thin-bedded turbidites to 39 m/day in the calcareous rocks (average values from the four test sites). At several places, discrete fault zones were identified as main hydraulic pathways between impacted streams and draining tunnels. This case shows that ignoring the hydrogeological conditions in construction projects can cause terrible damage, and the study presents an approach to better predict hydraulic impacts of draining tunnels in complex sedimentary rock settings.  相似文献   

Utilization of the non-fossil fuel target and its implications in China     

Shuwei Zhang  Nico Bauer 《Climate Policy》2013,13(3):328-344

China has pledged to meet a series of political targets on energy and environmental performance, including a target of a 15% non-fossil fuel share in total energy use by 2020. Achieving this target requires expansion of non-fossil energy and restraining energy use, which has implications for achieving the 40–45% carbon intensity reduction target. The present study outlines quantitative formulas to measure the nexus between the dynamics of GDP, energy, and carbon intensity. Considering a ‘likely’ scenario of the non-fossil fuel expansion envisioned by the Chinese government and a GDP growth rate of 8% per annum, the key to accomplishing both targets is to restrain energy consumption to attain an energy elasticity to GDP of approximately 0.53. Both targets can be achieved simultaneously with the existing non-fossil expansion plan and are within the ‘normal’ range of GDP growth seen in China over the long term. This is, however, less than the value realized over the last 10 years. To comply with the non-fossil fuel target, the potentially slower expansion of nuclear power capacity must be compensated for by other non-fossil options. Otherwise, there must be a greater attempt to decouple energy demand and economic growth in order to realize a smaller energy elasticity to GDP.

Policy relevance

China has pledged to achieve a 15% non-fossil fuel share and reduce its carbon intensity by 40–45% by 2020. The key to accomplishing both targets is to restrain energy consumption and promote the development of non-fossil fuels. The achievement of these two targets by 2020 is analysed between share of non-fossil fuel, CO₂ intensity of energy and GDP, and energy elasticity in relation to GDP. This analysis can inform the governmental energy and climate policy on the scale and pace of non-fossil fuel development, and the prerequisite regarding the energy elasticity to GDP to achieve the targets. The impacts of slower expansion of nuclear power capacity on the target achievement and implied elasticity of energy to GDP are also provided, which is close to the policy choice and actions of government on energy saving and emissions reduction.  相似文献   

Design and use of web lectures to enhance GIS teaching and learning strategies: the students’ opinions     

Kristien Ooms  Philippe De Maeyer  Bart De Wit  Ruben Maddens  Timothy Nuttens  Nico Van De Weghe 《制图学和地理信息科学》2013,40(3):271-282

The goal of this research is to design, use and evaluate a set of web lectures, specifically tailored to the needs of students in higher education who follow geographic information system -related courses. Since education in geographic information system includes theoretical concepts and practical experience, both of these teaching strategies will be implemented in the web lectures. The user-centered design approach is used in the design process to increase the acceptance of the web lectures and the motivation to use them: perceived usefulness and ease of use. The results show that the students appreciate the initial set of web lectures, but that they need to be motivated more to use them (especially when theoretical topics are covered). Students still value the “traditional” face-to-face lectures and see the web lectures as an ideal complement.  相似文献