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Based on a study of the German Ministry of Research and Technology in 1990 every year about 2.5 t of heavy metals are released per hectare of landfill by aqueous leaching. This leachate contains approximately 2000 t of heavy metals per year. Their decontaminations in accordance with the legal requirements represent an enormous potential for easing the burden on the environment. On the other hand, this potential opens new possibilities in the production and recycling of selected compounds. The composition of a given model solution corresponds to a landfill leachate resulting from a municipal dump leachate produced by an average German city. Actually, in most cases, a decontamination of such solutions occurs by the transfer of the problematic cations into insoluble compounds usually done by precipitation. The result of the procedure is an unspecific separation of all liquid components - and the "cycle of waste" (landfill- leaching-deposition) begins anew, certainly on a higher level. The objective of our work is the simultaneous separation of heavy metals from alkaline earth metals and iron in order to obtain a leachate which we can lead back to the landfill. The reactive extraction as a separation process offers the possibility of a selective separation of cations that is the separation of toxic - from unproblematic components and includes also the possibility of electrolysis or further winning processes to obtain the wished metals. For the realisation of extraction processes, several commercial extractants and technical equipments are available. Apart from iron, LIX 54 could be used advantageously for an extraction process - unfortunately without any considerable extraction of cadmium. But it is favourable to separate non toxic alkaline earth metals from problematic heavy metals. Such a complex task as the separation of cations from natural solutions cannot be solved easily in a one-step-extraction process. Better results should be obtained by the combination of different procedures, e.g. extraction, ion-exchange and precipitation.
Wo Wasser Weiden wachsen läßt : Witterungsbedingte Dynamik von Geosystemen der mongolischen Steppe
(2001)
Ausgleich nur auf dem Papier
(2001)
Die Völkerrechtsverantwortung des Bundesverfassungsgerichts : Bemerkungen zu Art. 100 Abs. 2 GG
(2001)
Ovlivnovani ucebni motivace
(2001)
Lehrende in Schulen
(2001)
The "Weighting Process" in Land Use Planning - Discussion of the Present Practice of "Weighting Out". Owing to the revision of the Building Code from January 1998 the impact regulation in land use planning is now established in the Building Law. This means the local governments have decision-making powers how to precisely implement the impact regulation. This, however, does not mean - as had been said in practice - that the concerns of nature and landscape can be "weighted out". On the contrary, the decision-making process has to include a detailed differentiation depending on the case, according to a verdict of the Supreme Administrative Court from 1997. The concerns of nature and landscape cannot be moved back as "not of furhter relevance". Only precisely described and insurmontable constraints allow cutbacks. Since compensation measures now can be carried out on the ground of adjacent local communities, a lack of sites available cannot be accepted as a reason. The paper makes clear why also in urban land use planning interference into nature has to be fully compensated for.
'Discours indirect libre', 'erlebte Rede' et autres sources de malentendus en linguistique textuelle
(2001)
Origine, histoire, évolution : l' actualité d'une histoire notionnelle des sciences du langage
(2001)
Impacts of agricultural land use on the environment are various and do not contribute to modifications of the ecology of central European landscapes. They do not only cause a progressive reduction of the number of plant ans animal specis typical for central Europe. Ever since the increasing intensification of farming, from the application of large amounts of fertilizers and pesticides to the use of increasingly larger machinery and progressive specialization there has also been an increase of other, hitherto little noticed environmental impacts. Heavy machinery and cultivation during disadvantageous weather will provoke soil compaction. Unvarying crop rotation systems and plouging of terrain too steep for it will increase water erosion. Due to groundwater lowering former peat lands are increasingly prone to desiccation and thus extremely susceptible to wind erosion. High rates of fertilizer application contiuously increase the risk of nitrate eluviation into the groundwater. These hazards are explained and measures of reduction are shown. The latter are indeed compatible with the aims of intensive farming but with less negative consequences for the environment. Above all they make sure that future generations will be able to continue farming the agricultural lands of central Europe that have been under cultivation for thousands of years.
A series of new poly-1,3,4-oxadiazoles has been synthesized by polycondensation reaction of hydrazine sulfate with a mixture of a dicarboxylic acid containing unsaturated bonds and a dicarboxylic acid containing silicon, by using methanesulfonic acid/phosphorus pentoxide as a reaction medium. These polymers were highly thermostable but they were only soluble in strong inorganic acids such as sulfuric or methanesulfonic ones. An alternative way was followed by using the corresponding dihydrazides containing unsaturated bonds and the corresponding diacid chloride containing silicon that reacted in N-methylpyrrolidinone (NMP) to give soluble silicon-containing unsaturated polyhydrazides, which were cyclodehydrated either by thermal or chemical treatment to give the corresponding polyoxadiazoles. Very thin coatings of polyhydrazides and polyoxadiazoles were deposited onto silicon wafers and they showed a very smooth surface, free of pinholes, when studied by atomic force microscopy (AFM). Some polyoxadiazole films showed strong blue photoluminescence.
We numerically investigate nonlinear asymmetric square patterns in a horizontal convection layer with up-down reflection symmetry. As a novel feature we find the patterns to appear via the skewed varicose instability of rolls. The time-independent nonlinear state is generated by two unstable checkerboard (symmetric square) patterns and their nonlinear interaction. As the bouyancy forces increase the interacting modes give rise to bifurcations leading to a periodic alternation between a nonequilateral hexagonal pattern and the square pattern or to different kinds of standing oscillations.
Schule in der kulturellen Vielfalt : Beobachtungen und Wahrnehmungen interkulturellen Unterrichts
(2001)
Urbild und Abbild : Untersuchungen zu Herrschaft und Weltbild in Altrußland 11. - 16. Jahrhundert
(2001)
Digital seismology tutor
(2001)