Determination of the conduit structure in a karst aquifer based on tracer data—Lurbach system,Austria     

Christine Kübeck  Piotr Jan Maloszewski  Ralf Benischke 《水文研究》2013,27(2):225-235

A structure model was used to analyse solute‐transport parameter estimates based on tracer breakthrough curves. In the model system, groundwater flow is envisioned to be organised in a complex conduit network providing a variety of short circuits with relative small carrying capacities along different erosion levels. The discharge through the fully filled conduits is limited owing to void geometries and turbulent flow; thus, a hierarchic overflow system evolves where conduits are (re‐)activated or dried up depending on the flow condition. Exemplified on the Lurbach–Tanneben karst aquifer, the applicability of the model approach was tested. Information derived from multi‐tracer experiments performed at different volumetric flow rates enabled to develop a structural model of the karst network, under constraint of the geomorphological and hydrological evolution of the site. Depending on the flow rate, groundwater is divided into up to eight flow paths. The spatial hierarchy of flow paths controls the sequence of flow path activation. Conduits of the topmost level are strongly influenced by reversible alteration processes. Sedimentation or blocking causes an overflow of water to the next higher conduit. Flow path specific dissolutional denudation rates were estimated using the temporal development of the partial discharge. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Isotopic and geochemical characteristics of groundwater in the Senegal River delta aquifer: implication of recharge and flow regime   总被引：3，自引：3，他引：0  

Moctar Diaw  Serigne Faye  Willibald Stichler  Piotr Maloszewski 《Environmental Earth Sciences》2012,66(4):1011-1020

Groundwater and surface water samples were collected to improve understanding of the Senegal River Lower Valley and Delta system, which is prone to salinization. Inorganic ion concentrations and environmental isotopes (¹⁸O, ²H and ³H) in groundwater, river, lake and precipitation were investigated to gain insight into the functioning of the system with regard to recharge sources and process, groundwater renewability, hydraulic interconnection and geochemical evolution. The geochemical characteristics of the system display mainly cation (Ca²⁺ and/or Na⁺) bicarbonated waters, which evolve to chloride water type; this occurs during groundwater flow in the less mineralized part of the aquifer. In contrast, saline intrusion and secondary brines together with halite dissolution are likely to contaminate the groundwater to Na–Cl type. Halite, gypsum and calcite dissolution determine the major ion (Na⁺, Cl⁻, Ca²⁺, Mg²⁺, SO₄ ²⁻ and HCO₃ ⁻) chemistry, but other processes such as evaporation, salt deposition, ion exchange and reverse exchange reactions also control the groundwater chemistry. Both surface water and groundwater in the system show an evaporation effect, but high evaporated signatures in the groundwater may be due to direct evaporation from the ground, infiltration of evaporated water or enriched rainwater in this region. The stable isotopes also reveal two types of groundwater in this system, which geomorphologically are distributed in the sand dunes (depleted isotopes) and in the flood plain (enriched isotopes). Consideration of the ³H content reinforces this grouping and suggests two mechanisms of recharge: contribution of enriched surface water in recharging the flood plain groundwater and, in the sand dunes area where water table is at depth between 8 and 13 m, slow recharge process characterized the submodern to mixed water.  相似文献   

The influence of shapes of the bodies on the dynamics of planetary and star systems     

Piotr Wąż 《Celestial Mechanics and Dynamical Astronomy》2006,96(3-4):159-167

The dynamics of planetary and star systems including perturbing forces due to the flattering and quadrupole distortion of the bodies is studied. The analytical model describing the perturbations which influence on the orbital motion of extrasolar planetary systems is presented. The calculations of the secular evolution of the mean orbital elements have shown that the effects related to the shape of the body are more important than the ones due to the quadrupole distortion.  相似文献   

Physics of the Earth by Frank D. Stacey and Paul M. Davis, fourth edition     

Marek Lewandowski 《Pure and Applied Geophysics》2009,166(12):2091-2092

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Testing a model of variability of X-ray reprocessing features in active galactic nuclei     

Piotr T. &#;ycki  Agata Ró&#;a&#;ska 《Monthly notices of the Royal Astronomical Society》2001,325(1):197-207

A number of recent results from X-ray observations of active galactic nuclei involving the Fe K α line (reduction of line variability compared with the X-ray continuum variability, the X-ray 'Baldwin effect') were attributed to the presence of a hot, ionized skin of an accretion disc, suppressing emission of the line. The ionized skin appears as a result of the thermal instability of X-ray irradiated plasma. We test this hypothesis by computing the Thomson thickness of the hot skin on top of the αP _tot Shakura–Sunyaev disc, by simultaneously solving the vertical structure of both the hot skin and the disc. We then compute a number of relations between observable quantities, e.g. the hard X-ray flux, amplitude of the observed reprocessed component, relativistic smearing of the K α line and rms variability of the hard X-rays. These relations can be compared with present and future observations. We point out that this mechanism is unlikely to explain the behaviour of the X-ray source in MCG–6-30-15, where there are a number of arguments against the existence of a thick hot skin, but it can work for some other Seyfert 1 galaxies.  相似文献   

Morphology and evolution of simulated and optical clusters: a comparative analysis     

Nurur Rahman †‡  Janusz Krywult  Patrick M. Motl  Piotr Flin  Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2006,367(2):838-850

We have made a comparative study of morphological evolution in simulated dark matter (DM) haloes and X-ray brightness distribution, and in optical clusters. Samples of simulated clusters include star formation with supernovae feedback, radiative cooling and simulation in the adiabatic limit at three different redshifts,   z = 0.0, 0.10  and 0.25. The optical sample contains 208 Abell, Corwin & Olowin (ACO) clusters within redshift,   z ≤ 0.25  . Cluster morphology, within 0.5 and 1.0 h ⁻¹ Mpc from cluster centre, is quantified by multiplicity and ellipticity.
We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened.
Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one.
Within   z ≤ 0.1  , we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters.  相似文献   

New Hormaphididae (Hemiptera, Aphidomorpha) from the Baltic Amber and its Palaeogeographic Significance     

Piotr WEGIEREK  Dagmara ?Y?A 《《地质学报》英文版》2011,85(3):521-527

The present study describes a new genus and species Unicohormaphis sorini, which belongs to the subfamily Cerataphidinae. The contemporary distribution of aphids belonging to the Hormaphididae family is summarized and analyzed. According to the obtained data, the climate warming in Eocene was conducive to the expansion of the family over the areas of Europe. Subsequent climate changes, resulting from epeirogenic and orogenic movements towards the end of Eocene, led to a considerable cooling and drying of climate in the northern hemisphere. These processes contributed to the shrinking down of areas covered by subtropical forests, which constituted the habitat of Hormaphididae (Cerataphidinae). Retaining their way of life, the Cerataphidinae were forced to limit their distribution, and the representatives of the family in Europe became completely extinct.  相似文献   

The anisotropy of galaxy orientation in the Coma/A1367 supercluster     

Piotr Flin 《Monthly notices of the Royal Astronomical Society》2001,325(1):49-54

The spatial orientations of the galactic planes for galaxies in the Coma/A1367 supercluster have been determined. Owing to the ambiguity in the determination of the inclination angle, two possible orientations of the normal to the galaxy plane were found. Two angles, the polar angle δ _D and the azimuthal angle η , describe the orientation of normals. The distribution of both angles has been checked for isotropy. It is shown that the distribution is not isotropic. The same alignment is observed for samples containing elliptical and lenticular galaxies and for samples containing only spirals, as well as for samples containing galaxies located in different parts of the supercluster. In the case of spiral galaxies, the anisotropy shows that galaxy rotation axes strongly favour alignment with the main plane of the supercluster. The projection of the rotation axes on to the main plane of the supercluster has a preferential direction pointing towards the supercluster, but this effect is weak. A comparison with theory is also presented.  相似文献   

Where will widening occur in an outwash braidplain? A new approach to detecting controls on fluvial lateral erosion in a glacierized catchment (north-western Spitsbergen,Svalbard)     

Piotr Weckwerth  Ireneusz Sobota  Katarzyna Greń 《地球表面变化过程与地形》2021,46(5):942-967

The dynamics of fluvial system evolution depend on fluvial processes and their driving forces associated with climatic variations, which affect changes in the morphology of river channels and floodplains. Neither channel slope and morphology, nor the properties of fluvial sediment have previously been considered as determinants of active braidplain widening on outwash plains (formed from valley/alpine glaciers and confined by pre-existing topography) in the High Arctic region and in the forefields of retreating glaciers. Factors determining widening of braidplain activity of the Waldemar River outwash (north-western Spitsbergen, Svalbard) were analysed on the basis of geomorphological, sedimentological, glaciological and meteorological research, and indicate significant multiple correlations between meltwater discharge, precipitation, braidplain width, morphology of the braided channel and the textural features of braidplain deposits. The capability of multivariate adaptive regression splines to detect these relationships was described, and threshold values were identified. The results indicate that the rate of active braidplain widening is proportional to the meltwater outflow in proglacial rivers, which can decrease despite a growing rate of glacial ablation. A proposed model enables us to predict zones of braidplain prone to widening activity in the High Arctic (humid) outwash fans and plains as well as fans developed in arid intermountain basins. The necessary conditions to activate braidplain widening processes were (1) spatial changes in the outwash feeding system due to glacier terminus retreat and (2) crossing the thresholds in passive factors (S and d₅₀) controlling lateral erosion intensity. As a result, the braidplain reached a new dynamic equilibrium, in which high-magnitude–low-frequency extreme meltwater discharges were of particular importance in terms of braidplain dynamics and are the dominant controls on the pattern of distributary channels.  相似文献   

High-Resolution Integrated Transport Model for Studying Surface Water–Groundwater Interaction     

Tabea Broecker  Vahid Sobhi Gollo  Aryeh Fox  Jörg Lewandowski  Gunnar Nützmann  Shai Arnon  Reinhard Hinkelmann 《Ground water》2021,59(4):488-502

Transport processes that lead to exchange of mass between surface water and groundwater play a significant role for the ecological functioning of aquatic systems, for hydrological processes and for biogeochemical transformations. In this study, we present a novel integral modeling approach for flow and transport at the sediment–water interface. The model allows us to simultaneously simulate turbulent surface and subsurface flow and transport with the same conceptual approach. For this purpose, a conservative transport equation was implemented to an existing approach that uses an extended version of the Navier–Stokes equations. Based on previous flume studies which investigated the spreading of a dye tracer under neutral, losing and gaining flow conditions the new solver is validated. Tracer distributions of the experiments are in close agreement with the simulations. The simulated flow paths are significantly affected by in- and outflowing groundwater flow. The highest velocities within the sediment are found for losing condition, which leads to shorter residence times compared to neutral and gaining conditions. The largest extent of the hyporheic exchange flow is observed under neutral condition. The new solver can be used for further examinations of cases that are not suitable for the conventional coupled models, for example, if Reynolds numbers are larger than 10. Moreover, results gained with the integral solver provide high-resolution information on pressure and velocity distributions at the rippled streambed, which can be used to improve flow predictions. This includes the extent of hyporheic exchange under varying ambient groundwater flow conditions.  相似文献