Geomaterials related to photovoltaics: a nanostructured Fe-bearing kuramite,Cu<Subscript>3</Subscript>SnS<Subscript>4</Subscript>

The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)₃SnS₄, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu⁺, Sn⁴⁺ and Fe³⁺. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes.     

Review: The state-of-art of sparse channel models and their applicability to performance assessment of radioactive waste repositories in fractured crystalline formations

Laboratory and field experiments done on fractured rock show that flow and solute transport often occur along flow channels. ‘Sparse channels’ refers to the case where these channels are characterised by flow in long flow paths separated from each other by large spacings relative to the size of flow domain. A literature study is presented that brings together information useful to assess whether a sparse-channel network concept is an appropriate representation of the flow system in tight fractured rock of low transmissivity, such as that around a nuclear waste repository in deep crystalline rocks. A number of observations are made in this review. First, conventional fracture network models may lead to inaccurate results for flow and solute transport in tight fractured rocks. Secondly, a flow dimension of 1, as determined by the analysis of pressure data in well testing, may be indicative of channelised flow, but such interpretation is not unique or definitive. Thirdly, in sparse channels, the percolation may be more influenced by the fracture shape than the fracture size and orientation but further studies are needed. Fourthly, the migration of radionuclides from a waste canister in a repository to the biosphere may be strongly influenced by the type of model used (e.g. discrete fracture network, channel model). Fifthly, the determination of appropriateness of representing an in situ flow system by a sparse-channel network model needs parameters usually neglected in site characterisation, such as the density of channels or fracture intersections.     

How appropriate is the Thiem equation for describing groundwater flow to actual wells?

The Thiem equation of radial groundwater flow to a well is more than 100 years old and is still commonly used. Here, deviations caused by some of its simplifications are quantified by comparing the analytical to a numerical model that allows the implementation of more complex geometries. The assumption of horizontal flow in the Thiem equation, which necessitates uniform inflow over the entire screen length of the fully penetrating well, was found to cause deviations from actual pumping wells where the pump is placed above the screen, resulting in non-uniform inflow and additional drawdown. The same applies to partially penetrating wells, where inflow peaks and additional drawdown occur, especially when the well is screened in the lower part of the aquifer. The use of the Thiem equation in the near-field of a well should thus be restricted to situations where the screen inflow is relatively uniformly distributed, e.g. when it covers large portions of the aquifer thickness. The presence of a gravel pack and a background gradient, on the other hand, are of limited importance.     

Der Stand des Problems der Entstehung des Mansfelder Kupferschiefers

Ohne Zusammenfassung     

Praktische Geologie und Allgemeinheit

Ohne Zusammenfassung     

Der wasserhaushalt des Mittelländischen Meeres und der Ostsee in vergleichender Betrachtung

Summary Recent research, and particularly that undertaken by the «Kieler Institut für Meereskunde», has suggested a re-examination of the water households of both the Mediterranean and the Baltic Seas. It is hoped that a comparative study of the two may contribute to a better understanding of the maritim-meteorological and oceanographic characteristics of either sea. The latest rain maps byW. Daume, F. Möller, andW. Brogmus show an average annual amount of rainfall of 345 mm in the Mediterranean, and 474 mm in the Baltic. In both cases these figures are roughly 15 per cent lower than what authors have so far assumed them to be. The figures for the fresh-water sypply from the land have also been revised in recent publications byDaume andBrogmus, the annual figures for the Mediterranean being 350 km³ (i. e. 129mm in hight), while the annual figure for the Baltic is 480 km³ (i. e. 1243 mm in hight). These figures have been used together with recent, but still largely hypothetical, figures for the difference between in- and outflow at the straits (Gibraltar, Bosphorus, the Belts, and the Sound), to calculate the evaporation from the basic water-household equation. The annual evaporation figure is 1450 mm for the Mediterranean, and only 473 mm for the Baltic. Again, these figures differ from former estimates, but they are confirmed by other considerations, and calculations of maritime meteorology. It is with these new figures in mind that the author finally goes into the question of the hydrographic and climatic effects of a damming-up of the above-mentioned straits.Soergel's fantastic «Atlantropa» project, already criticised bytroll, van Einerm andDaume, is briefly treated from the point of view of the water household and is found to be largely impracticable. It is pointed out that the systematic collection of further information on the meteorological and oceanographic conditions of the two seas is urgently needed for the sake of further reducing the margin of error in the above calculations.

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Zusammenfassung Auf Grund neuerer, besonders auch im Kieler Institut für Meereskunde durchgeführter Untersuchungen wird der Versuch gemacht, die Wasserhaushalte des Mittelländischen Meeres und der Ostsee einer Revision zu unterziehen und durch eine vergleichende Betrachtung zu einem vertieften Verständnis der maritim-meteorologischen und ozeanographischen Besonderheiten beider meere beizutragen. Aus neuen Regenkarten vonW. Daume, F. Möller undW. Brogmus ergibt sich die mittlere Niederschlagshöhe für das Mittelmeer zu 345 mm/Jahr und für die Ostsee zu 474 mm/Jahr, das sind in beiden Fällen um rd. 15% niedrigere Werte, als frühere Autoren vermuteten. Auch für die Süßwasserzufuhr vom Lande werden im Anschluss an die neuen Arbeiten vonDaume undBrogmus neue Zahlen geboten: für das Mittelmeer 350 km³/Jahr (=129 mm/Jahr Wasserhöhe), für die Ostsee hingegen 480 km³/Jahr (=1243 mm/Jahr Wasserhöhe). Unter Benutzung dieser Zahlen und neuerer z.T. zwar noch sehr hypothetischer Angaben über die Differenz von Ausstrom und Einstrom in den ozeanischen Verbindungsstraßen (Straße von Gibraltar, Bosporus, Belte und Sund) wird die Verdunstung aus der Grundgleichung des Wasserhaushaltes rechnerisch ermittelt und für das Mittelmeer zu 1450 mm/Jahr, für die Ostsee hingegen zu nur 473 mm/Jahr gefunden, Werte, die von früheren Schätzungen abweichen, aber auch durch andere maritim- meteorologische Ueberlegungen und Berechnungen gestützt werden können. Zum Schluss wird die Frage der hydrographischen und klimatischen Auswirkung der Abdämmung der genannten Meeresengen vom Standpunkte dieser neuen Wasserbilanzen kritisch geprüft. Das phantastische «Atlantropa»-ProjektSoergels wird im Anschluss an die kritischen Betrachtungen vonTroll, van Einerm undDaume vom Standpunkte des Wasserhaushalts kurz beleuchtet und seine Durchfürhung in grossen Teilen als unmöglich angesehen. Weitere systematische maritimmeteorologische und ozeanographische Beobachtungen werden für beide Nebenmeere als dringend erwünscht bezeichnet, um die in dem Bilanzen noch bestehenden Unsicherheiten weiter zu verringern.