Reflection response for normal incidence probing of vertically nonhomogeneous media

A time domain synthetic reflection seismogram is detailed and, as a limiting condition on this model, the analytic reflection impulse response for a one-dimensional lossless acoustic medium with piecewise continuous acoustic impedance is obtained. This analytic impulse response solution, in the structure of a sum of terms by order of reflection, provides insight to some of the poorly understood aspects of acoustic reflections from stratified and smoothly varying media as may be encountered in shallow marine sediments and elsewhere. It offers as well an approach for the inverse problem of extracting acoustic impedance profiles from reflection response data, though other effects (such as wavefront spreading, dispersive and absorptive attenuation, and wavelet broadening attendant with pulse propagation through a medium) need to be accommodated.     

Photo‐identification of short‐beaked common dolphins (Delphinus delphis) in north‐east New Zealand: A photo‐catalogue of recognisable individuals

Photo‐identification has been established as a helpful tool in cetacean research. However, no study to date has attempted to apply this method to short‐beaked common dolphins (Delphinus delphis L.). We present here the results of two studies that were conducted concurrently in Mercury Bay and the Hauraki Gulf on the north‐east coast of New Zealand's North Island. Methods for distinguishing between individual dolphins are discussed. Sighting records of recognisable individuals indicate that some common dolphins move between Mercury Bay and the Hauraki Gulf (100 km distance), as well as between Mercury Bay and Whakatane (200 km distance). Common dolphin abundance and site fidelity appeared to be greater in the Hauraki Gulf than in Mercury Bay. A selection of photographs of distinct individuals is presented to allow future studies to compare their sighting records to ours, which may help establish the extent of home ranges, site fidelity, and possibly even longevity for common dolphins.     

Assessing housing growth when census boundaries change

The US Census provides the primary source of spatially explicit social data, but changing block boundaries complicate analyses of housing growth over time. We compared procedures for reconciling housing density data between 1990 and 2000 census block boundaries in order to assess the sensitivity of analytical methods to estimates of housing growth in Oregon. Estimates of housing growth varied substantially and were sensitive to the method of interpolation. With no processing and areal‐weighted interpolation, more than 35% of the landscape changed; 75–80% of this change was due to decline in housing density. This decline was implausible, however, because housing structures generally persist over time. Based on aggregated boundaries, 11% of the landscape changed, but only 4% experienced a decline in housing density. Nevertheless, the housing density change map was almost twice as coarse spatially as the 2000 housing density data. We also applied a dasymetric approach to redistribute 1990 housing data into 2000 census boundaries under the assumption that the distribution of housing in 2000 reflected the same distribution as in 1990. The dasymetric approach resulted in conservative change estimates at a fine resolution. All methods involved some type of trade‐off (e.g. analytical difficulty, data resolution, magnitude or bias in direction of change). However, our dasymetric procedure is a novel approach for assessing housing growth over changing census boundaries that may be particularly useful because it accounts for the uniquely persistent nature of housing over time.     

Radon and remediation measures near Băiţa-Ştei old uranium mine (Romania)

B?i?a-?tei mine is an open pit mine in NW Romania (West Carpathian Mountains). It was the largest surface uranium deposit in the world. Two means of uranium transport and dissemination were used over time. The first was the natural way, represented by transportation of geological sediments by Cri?ul-B?i?a River that crosses the B?i?a surface deposit. These sediments were used as building materials (stone, gravel, sand). The second way was related to the people living in this valley, who used also the uranium waste as building material. The preliminary indoor radon concentrations measured in the buildings ranged from 40 to 4000 Bq m^?3 with a mean value of 241 Bq m^?3. A focused radon survey facilitated the selection of 20 houses with the highest indoor radon that were therefore proposed for remediation. To find the radon sources of these houses, systematic investigations on radon were performed. The remedial measures for these 20 houses were tested on a chosen pilot house.     

Investigation of the geochemical impact of CO2 on shallow groundwater: design and implementation of a CO2 injection test in Northeast Germany

A small scale and temporally limited CO₂ injection test was performed in a shallow aquifer to investigate the geochemical impact of CO₂ upon such aquifers and to apply and verify different monitoring methods. Detailed site investigation coupled with multiphase simulations were necessary to design the injection experiment and to set up the monitoring network, before CO₂ was injected over a ten-day period at three injection wells, at a depth of 18?m below surface level into a quaternary sand aquifer located close to the town of Wittstock in Northeast Germany. Monitoring methods comprised groundwater sampling and standard analyses, as well as trace element analyses and isotope analyses; geoelectrical borehole monitoring; passive samplers to analyse temporally integrated for cations and multi-parameter probes that can measure continuously for dissolved CO₂, pH and electrical conductivity. Due to CO₂ injection, total inorganic carbon concentrations increased and pH decreased down to a level of 5.1. Associated reactions comprised the release of major cations and trace elements. Geoelectrical monitoring, as well as isotope analyses and multi-parameter probes proved to be suitable methods for monitoring injected CO₂ and/or the alteration of groundwater.     

Development of a sharp interface model that simulates coastal aquifer flow with the coupled use of GIS

A simulation program, which works seamlessly with GIS and simulates flows in coastal aquifers, is presented in the present paper. The model is based on the Galerkin finite element discretization scheme and it simulates both steady and transient freshwater and saltwater flow, assuming that the two fluids are separated by a sharp interface. The model has been verified in simple cases where analytical solutions exist. The simulation program works as a tool of the GIS program, which is the main database that stores and manages all the necessary data. The combined use of the simulation and the GIS program forms an integrated management tool offering a simpler way of simulating and studying saline intrusion in coastal aquifers. Application of the model to the Yermasogia aquifer illustrates the coupled use of modeling and GIS techniques for the examination of regional coastal aquifer systems.

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Resumen Se ha desarrollado un modelo casi tridimensional de elementos finitos para simular el flujo de agua dulce y salada, tanto en régimen estacionario como en transitorio, en sistemas acuíferos costeros, bajo la hipótesis de separación por medio de una interfaz abrupta. Las ecuaciones del modelo han sido discretizadas mediante un esquema de Galerkin de discretización en elementos finitos. El modelo ha sido verificado en casos sencillos para los que existe solución analítica. Todos los datos necesarios se introducen y gestionan con un Sistema de Información Geográfica [SIG] por ordenador. El programa de simulación forma parte del programa de SIG, constituyendo una herramienta integrada de gestión para estudiar la intrusión salina en acuíferos costeros. La aplicación del modelo al acuífero de Yermasogia ilustra el uso acoplado de las técnicas de modelación y de SIG con el fin de examinar sistemas acuíferos costeros a escala regional.

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Résumé Pour étudier un système aquifère côtier, nous avons développé un modèle aux éléments finis en quasi 3-D qui simule les écoulements deau douce et deau salée en régime aussi bien permanent que transitoire. Les équations qui les régissent sont discrétisées par un schéma de discrétisation de Garlekin aux éléments finis. Le modèle a été vérifié dans des cas simples où il existe des solutions analytiques. Toutes les données nécessaires sont introduites et gérées grâce à un logiciel de gestion de SIG. Le programme de simulation est utilisé comme un outil du logiciel de SIG, constituant ainsi un outil de gestion intégrée dont le but est de simuler et détudier lintrusion saline dans les aquifères côtiers. Lapplication du modèle à laquifère de Yermasogia illustre lutilisation couplée de la modélisation et des techniques de SIG pour létude des systèmes aquifères côtiers régionaux.

     

Influence of localised igneous activity on cleat dawsonite formation in Late Permian coal measures, Upper Hunter Valley, Australia

Stable (δ¹³C and δ¹⁸O) and radiogenic ⁸⁷Sr/⁸⁶Sr isotopic data have been used to investigate the origin of cleat dawsonite (NaAlCO₃(OH)₂) in the Late Permian Wittingham Coal Measures of the Upper Hunter region in the Sydney Basin, New South Wales. The δ¹³C_PDB values have a narrow range (− 1.7‰ to + 2.4‰), with an average of + 0.3‰, suggesting a magmatic source for the carbon. In contrast, δ¹⁸O_SMOW values have a wide range (+ 13.6‰ to + 19.8‰), and decrease systematically with decreasing distance from a major intrusion. This systematic variation reflects establishment of localised hydrothermal cells. Water–rock interaction between fluids associated with these hydrothermal cells, and Rb-poor volcaniclastic detritus in the coal measures, produced mantle-like ⁸⁷Sr/⁸⁶Sr (0.705032 to 0.706464) in the dawsonite.     

Biodiversität und Ökologie aquatischer Oomycetes‐Arten im Auesee und in der Fulda in Kassel (Hessen)

Biodiversity and Ecology of Species of Aquatic Oomycetes in the Aue Lake and the River Fulda in Kassel (Hessen) In this study, we record diversity and ecology of aquatic Oomycetes in the Aue Lake and the river Fulda in Kassel (Hesse, Germany). We monthly collected water samples of both water bodies from July 2003 to June 2004. The baiting method was used to gain an insight into the occurrence of aquatic Oomycetes. A total of 14 species of aquatic Oomycetes belonging to the orders Saprolegniales, Leptomitales and Olpidiopsidales could be isolated of both water bodies. Numerous saprophytic isolates of Rhizophydium Schenk (Chytridiomycetes), Rhizophydium carpophilum (Zopf) Fischer, parasitic on Oomycetes, and additionally one species of Plasmodiophoromycetes, Woronina polycystis Cornu could be isolated. Many isolates of Saprolegniales attributable to the genera Achlya Nees, Dictyuchus Leitgeb, Saprolegnia Nees and Pythium Pringsheim (Pythiales), which could only be identified on generic level, could be isolated as well. The species were examined and discussed with respect to their occurrence in the stagnant water Aue Lake and/or in the running water of the river Fulda. Half of the isolated species only occurred in one of the water bodies. In this study the occurrence of Achlya proliferoides Coker could be documented for Germany for the first time. The trophic status of the Aue Lake and of the classification of water quality of the river Fulda were determined by limnological‐chemical parameters obtained by simultaneous investigations of both water bodies.