Bestimmung geringer Wassergehalte in getrocknetem Klärschlamm mit Hilfe der Karl-Fischer-Titration     

J. Bortlisz  K. Rüther  H. Matschiner  M. Hahn 《洁净——土壤、空气、水》1995,23(3):104-110

Determination of Low Water Contents in Dried Sludge with the Help of Karl Fischer Titration The accomplished investigations lead to the conclusion that direct water detection in sludge is impossible. This is due to the numerous possible reactants present. Even the extraction of the water by an inert solvent did not permit any realistic deductions. The water detection in sludge requires an external extraction. This may be realized by means of an additional extracting gas or the gaseous phase of the Karl Fischer reagent. The latter method was realized with the apparatus made by the company ECH Elektrochemie Halle. This alternative offers the benefit of avoiding a separate desiccation of the extracting gas. By means of a temperature gradient, the optimum heating conditions for the extraction of water from sludge may be determined. As there are only small quantities of water to be detected in the dried sludges, the best possible method seems to be microcoulometry.  相似文献   

Modelling of activated sludge systems Von Derin Orhon und Nazik Artan Technomic Publishing AG,Basel, 1994, ISBN 1-56676-101-8, 601 S., hardcover,sfr 181,—     

Ch. Wolter  H. H. Hahn 《洁净——土壤、空气、水》1995,23(4):187-187

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A comparison of stygofauna communities inside and outside groundwater bores   总被引：6，自引：2，他引：6  

Hans Jürgen Hahn  Dirk Matzke 《Limnologica》2005,35(1-2):31-44

Sampling stygofauna is both time consuming and labour intensive. The challenge is to get samples from as many bores as possible within a limited time. The essential assumption for this is that faunal communities inside bores are comparable and representative of the communities outside.To compare relative abundance, taxonomic richness and community composition of the fauna inside groundwater bores to the fauna of the surrounding aquifer, 20 monitoring bores in Palatinate, southwestern Germany, were sampled twice in 1 month. Initially, a sample of 4 l of water was collected from the bottom of each bore. A further sample of 51 l was collected from the groundwater surrounding the bore using a pneumatic piston pump with double packer sampler.Water chemistry inside and outside the bore was similar, but the relative amounts of sediments within the bores were higher compared to those from outside. Relative abundances of fauna inside the bores were higher than in the aquifer, but taxonomic composition was similar with the exception of the proportions of nematodes and amphipods, which were higher inside. As a result, the proportions of cyclopoids were lower inside. Higher nematode proportions are explained partially by the nearly complete extraction of bore sediment. A “habitat heterogeneity effect” states that in heterogeneous aquifers with few suitable habitats, faunal distribution is supposed to be extremely patchy. Thus, detritus accumulates in bores, attracting animals and providing “habitat islands” in the groundwater. This effect could explain the higher amphipode proportions inside the bores, which were generally more frequently populated than the surrounding groundwater. As a consequence, fauna is thought to be nearly absent from groundwater, where suitable habitats are lacking. In those sparsely populated aquifers, samples representative of the aquifer taxonomic richness and composition can only be collected by removing large volumes of water, or by sampling the bottom of bores. These findings also suggest that the use of unbaited colonisation chambers or traps in the groundwater, which are comparable with bores, would seem to be a promising approach.  相似文献   

Unbaited phreatic traps: A new method of sampling stygofauna     

Hans Jürgen Hahn   《Limnologica》2005,35(4):248-261

(1) A new method of sampling stygofauna is presented, along with some data derived from applications in the field. Numerous bores were sampled for fauna, water and bacteria, down to a depth of 7.50 m. Two or 3 unbaited traps were fixed to a central pole within the bore. The traps consist of an inert plastic chamber with holes in the upper parts and gaskets near the bottom and near the lid of each trap. The content of the traps was emptied monthly using a pump.

(2) While the taxonomic composition of the trap samples seemed to be comparable to the surrounding groundwater, estimation of abundances in the traps might differ, with a potential over-estimation in the traps, in particular in sparsely populated aquifers. Detailed comparative studies on the performance of the method are, as yet, lacking.

(3) Trap data of invertebrate communities reflect hydraulic changes, and highest abundances and taxa richness were found near the water table. They decreased rapidly with depth, implying that small-scale stratified sampling is possible.

(4) The technique is cheap, reliable, simple and rapid to use, and allows simultaneous sampling of hydro-chemical, faunal and microbial samples. The method seems to be suitable for a wide range of sub-surface waters, where the water table is shallower than 8 m.

Wal-Mart and Aldi: Two Retail Giants in Germany     

Ulrike Gerhard  Barbara Hahn 《GeoJournal》2005,62(1):15-26

Wal-Mart entered the German market at the end of 1997 but is still running at a loss in its 92 stores. This article tests the hypothesis that there are two main reasons for Wal-Mart’s problems in Germany. First of all, Wal-Mart is competing against very strong and well established deep discounters, especially Aldi. Secondly, there is the difference between the so-called Wal-Mart culture and German customer values. So far, Wal-Mart has not managed to close this gap or create a positive image in Germany. The first part of the article describes the differences between the two retail companies Wal-Mart and Aldi, whereas the second part focuses on the consumer perspective. Four hundred people were interviewed on the phone about their shopping behaviour in the city of Würzburg (northern Bavaria, 140,000 inhabitants). This survey is part of an international study also undertaken in Canada, Great Britain and China.  相似文献   

RBCA Closure at DNAPL Sites     

Joseph W. Sheahan  CPG    Roy O. Ball  P.E.  Melinda W. Hahn 《Ground Water Monitoring & Remediation》1998,18(3):78-81

The closure of sites with identified or suspected DNAPL (dense nonaqueous phase liquids) under the requirements of the Resources Conservation and Recovery Act of 1976 (RCRA), or the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) has not been well defined. With respect to RCRA, the U.S. Environmental Protection Agency (EPA) has required that all contamination must be removed at closure such that no residual risk to human health or the environment remains. Therefore, even though many states administering the RCRA program have adopted or are considering Risk-Based Corrective Action (RBCA) procedures (including the statistical methods described in SW-846) for RCRA closure, the treatment of DNAPL is, at best, challenging.
The methodology for closure in CERCLA is described in "Risk Assessment Guidelines for Super-fund (RAGS)," which requires that risks above the National Contingency Plan criteria must be remediated, preferably by on-site or in situ destruction. Most risk-based Brownfield or voluntary cleanup programs do not provide any explicit allowance for DNAPL. However, while the ASTM methodology for RBCA in E1739-95 (ASTM 1995) does not explicitly treat the problem of DNAPL, a basic framework for DNAPL assessment is implicitly provided.
A uniform methodology for RBCA closure of VOC (volatile organic compounds) DNAPL sites can be used to achieve the program objectives of RCRA, CERCLA, and Brownfield or voluntary cleanup programs. The regulatory acceptance of the application of RBCA methods to DNAPL sites will require education and discussion, but the use of a uniform methodology should facilitate acceptance.  相似文献   

Tidal disruption of strengthless rubble piles—a dimensional analysis     

Joseph M. Hahn  Terrence W. Rettig 《Planetary and Space Science》1998,46(11-12)

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Analysis of remedial alternatives of the Nanji Landfill,Korea   总被引：1，自引：0，他引：1  

Jeonsang Hahn 《Environmental Geology》1996,28(1):12-21

 This paper presents an analysis of various remedial alternatives for a representative waste disposal site causing serious adverse affects to the surrounding soil and surface and groundwater systems and discusses the application of this approach in a case study. The numerical flow model along with the transport model in three dimensions were utilized to simulate current flow conditions at the site and its vicinity for calibration and to provide the analysis results for various remedial alternatives, such as top capping, vertical barrier, extraction, and hydrodynamic control. While the development of remedial alternatives and the selection of the most effective remedial measures are highly site-specific, the approach and methodology presented in this paper have general applicability. The conditions outlined in this study are used by environmental engineers and planners who incorporated economic and engineering decisions and public acceptance for various remedial measures considered; they also provide insight into the difficulties and special considerations associated with modeling and analyzing remedial alternatives. Received: 19 September 1995 · Accepted: 6 November 1995  相似文献   

Automatic Surface Reconstruction Based on the Fusion of Fuzzy Logic and Robust Estimation Techniques     

Farhad Samadzadegan  Ali Azizi  Caro Lucas  & Michael Hahn 《The Photogrammetric Record》2002,17(100):651-674

Automatic surface reconstruction by means of digital image matching essentially involves computation in both image and object spaces. In image space, image matching is performed according to certain radiometric and geometric similarity criteria for conjugate point determination. The matching operations may therefore be regarded as decision–making processes. In practice, however, the similarity criteria for conjugate point determination demonstrate non–deterministic behaviour. Thus, the nature of these decision–making processes is more compatible with fuzzy reasoning concepts. In object space, on the other hand, surface reconstruction procedures, which operate on the basis of previously determined conjugate points, are essentially deterministic in nature and hence demand rigorous geometric modelling. In this paper, a new approach for automatic surface modelling is proposed, based on two different mathematical treatments: a fuzzy logic reasoning method for the conjugate point determination in image space; and a robust finite elements approach for the surface modelling in object space. Tests carried out on real data demonstrate the high potential of the strategy proposed.  相似文献   

Physics and chemistry of comets     

Gerhard J. Hahn 《Astrophysics and Space Science》1991,181(2):335-336

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