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11.
Keller LP Bajt S Baratta GA Borg J Bradley JP Brownlee DE Busemann H Brucato JR Burchell M Colangeli L d'Hendecourt L Djouadi Z Ferrini G Flynn G Franchi IA Fries M Grady MM Graham GA Grossemy F Kearsley A Matrajt G Nakamura-Messenger K Mennella V Nittler L Palumbo ME Stadermann FJ Tsou P Rotundi A Sandford SA Snead C Steele A Wooden D Zolensky M 《Science (New York, N.Y.)》2006,314(5806):1728-1731
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust. 相似文献
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Georg Henner Tubeuf Y. Schüpfer und Fr. Moll 《Forstwissenschaftliches Centralblatt》1928,50(11):374-384
Ohne Zusammenfassung 相似文献
13.
Sandford SA Aléon J Alexander CM Araki T Bajt S Baratta GA Borg J Bradley JP Brownlee DE Brucato JR Burchell MJ Busemann H Butterworth A Clemett SJ Cody G Colangeli L Cooper G D'Hendecourt L Djouadi Z Dworkin JP Ferrini G Fleckenstein H Flynn GJ Franchi IA Fries M Gilles MK Glavin DP Gounelle M Grossemy F Jacobsen C Keller LP Kilcoyne AL Leitner J Matrajt G Meibom A Mennella V Mostefaoui S Nittler LR Palumbo ME Papanastassiou DA Robert F Rotundi A Snead CJ Spencer MK Stadermann FJ Steele A 《Science (New York, N.Y.)》2006,314(5806):1720-1724
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples. 相似文献
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Catrina Cofalla Sebastian Hudjetz Sebastian Roger Markus Brinkmann Roy Frings Jan W?lz Burkhard Schmidt Andreas Sch?ffer Ulrike Kammann Markus Hecker Henner Hollert Holger Schüttrumpf 《Journal of Soils and Sediments》2012,12(3):429-442
Purpose
Flood events are expected to increase both in intensity and frequency due to climate change in the near future. From an environmental toxicology perspective, there is concern that such flood events could lead to the remobilization of contaminated sediment layers in rivers. The aim of this pilot study was to establish a novel and interdisciplinary framework combining methods of hydrodynamic engineering and ecotoxicological assessment to enable investigation of the potential risks associated with such remobilization events.Materials and methods
Formulated sediment was prepared according to OECD guideline 218 and spiked with a mixture of four polycyclic aromatic hydrocarbons (phenanthrene, chrysene, pyrene, benzo[a]pyrene) at concentrations of 3.3?C8.3?mg?kg?1 dry weight. Rainbow trout (Oncorhynchus mykiss) were exposed as test animals to re-suspended sediments in three out of five experiments. The experiments were carried out in an annular flume designed to investigate transport behaviour of fine-grained sediments. Several physicochemical (e.g. pH) and sedimentological (e.g. turbidity) parameters were measured to characterise environmental conditions and erosion behaviour of sediments. Furthermore, exposure concentrations were measured by means of an in vitro assay (7-ethoxyresorufin-o-deethylase (EROD), RTL-W1 cell assay) and chemical analysis.Results and discussion
Preparation and spiking of large amounts of formulated sediments were feasible but not practical. Successful spiking could be confirmed by the bioanalytical methods with the spiked sediments showing significantly elevated EROD induction compared to control sediments. Conditions within the annular flume remained stable throughout all experiments and were adequate to support rainbow trout. Flood events were successfully simulated, resulting in re-suspension of formulated sediment. Different erosion behaviours of sediments during the simulated flood events were observed and could be associated with changes in microbial composition of sediments due to differences in storage conditions. Therefore, maintaining constant storage conditions of formulated sediments is crucial to enable consistency and comparability among erosion experiments.Conclusions
This study clearly demonstrated the feasibility of a combined hydro-toxicological approach in support of the investigation of the potential ecotoxicological relevance of sediment re-suspension events. However, based on the results presented here, it is recommended to include additional physicochemical parameters, such as redox potential and conductivity, and to extend the experimental setup to natural sediments and different aquatic organisms. Future studies will use natural sediments containing representative microbial communities and extracellular polymeric substances to enable extrapolation from the annular flume to conditions in natural flowing waters. 相似文献17.
Hanno Zielke Thomas-Benjamin Seiler Sabine Niebergall Erik Leist Markus Brinkmann Denise Spira Georg Streck Werner Brack Ute Feiler Thomas Braunbeck Henner Hollert 《Journal of Soils and Sediments》2011,11(2):352-363
Purpose
Traditionally, methods for sediment extractions are characterised using chemical analyses. However, in order to evaluate sediment extracts with regard to biological effects and, thus, bioaccessibility, extraction methods have to be compared to effect data obtained from experiments with in situ exposure scenarios, i.e., sediment contact tests. This study compares four extraction methods and sediment contact test data from a previous project with respect to predictive power in the fish embryo test with zebrafish (Danio rerio).Materials and methods
A natural and an artificial sediment spiked with a mixture of six organic pollutants (2,4-dinitrophenol, diuron, fluoranthene, nonylphenol, parathion and pentachlorophenol) were extracted using (a) membrane dialysis extraction (MDE), (b) a Soxhlet procedure, (c) hydroxypropyl-??-cyclodextrin (HPCD) or (d) Tenax®-TA. Whereas the former two are regarded being exhaustive with respect to non-covalently bound contaminants, the latter two are considered to predict bioaccessibility. Resulting extracts were tested in the fish embryo assay with D. rerio for embryotoxic and teratogenic potential.Results and discussion
Mortalities caused by organic extracts from Soxhlet extraction and MDE were high. However, HPCD extracts turned out to be at least as effective as extracts obtained with these two methods. One possible reason might be short ageing time of the spiked sediments. Only Tenax®-TA extracts gave results comparable to the sediment contact assay for natural sediment, but revealed low reproducibility. Significant differences between natural and artificial sediment were found for extracts obtained with techniques using native (i.e., non-freeze-dried) sediments, i.e., HPCD and Tenax®-TA. In contrast, MDE and Soxhlet extracts used freeze-dried sediment and did not differentiate between natural and artificial sediment. Therefore, freeze-drying has likely altered and equalised sediment properties that influence accessibility, such as composition of bacterial communities and organic matter quality.Conclusions
Four extraction methods were successfully characterised with respect to their stringency and predictiveness for bioaccessibility. MDE was confirmed as an alternative to Soxhlet extraction. High mortalities induced by HPCD extracts underline the need to include ageing into consideration when assessing sediments. Although Tenax®-TA may basically be used to predict bioaccessibility in the fish embryo test, the high variability observed warrants further investigation of the relation between effect and extractability. Apparently, freeze-drying can severely affect sediment properties, potentially eliminating individual properties of natural sediments. 相似文献18.
Arnold V. Hallare Thomas-Benjamin Seiler Henner Hollert 《Journal of Soils and Sediments》2011,11(1):141-173
Purpose
Sediments serve as integral and dynamic parts of our aquatic systems. Within the last 15 to 20 years, however, the scientific community has begun noticing deterioration of sediment quality at an alarming rate worldwide. Sediments are now harboring hazardous pollutants that can directly influence water quality, thereby creating very stressful conditions for aquatic life. As a consequence, global efforts were initiated in the early 1970s, to find ways to assess sediment quality. Because of their obvious ecological and economic significance, fish have remained a major taxonomic group for appraising the general quality of aquatic systems. However, for sediment risk assessment, fish have lagged behind invertebrates due to their mobility and generally, pelagic lifestyle. To our knowledge, this is the first paper that comprehensively presents and reviews the versatile role of fish in assessing the state of health of aquatic sediments. 相似文献19.
Es wurde untersucht, wie sich Zulagen Ca-verseifter (Ca-S), veresterter (TG) und freier ralmölfettsäuren (FPFS) auf pansenphysiologische und verdauungsphysiologische Parameter beim Wiederkäuer auswirken. Dazu dienten Untersuchungen mit Hilfe des Pansensimulationssystems “RUSITEC” und Stoffwechselversuche an ausgewachsenen Merinolandschafen. In den RUSITEC-Untersuchungen führten Fettzulagen von 6–11% in der Rations-TS bei Konstanthaltung des Futter- und Flüssigkeits-Turnovers zur Reduzierung der Protozoen in der Rangfolge Ca-S < TG < FPFS und zur Steigerung der Bakterienzahl in umgekehrter Rangfolge. Die durch Fettzulagen verursachte Verschiebung in der Mikrobenpopulation führte zu keiner Veränderung der NH3-N-Fixation, Mikrobenmassesynthese und Abbaubarkeit der Gerüstsubstanzen. In einem 12-wöchigen Stoffwechselversuch an Schafen wurden einer Grundration 140 g (= 10% i. d. TS) der beschriebenen Fette zugelegt. Die Verdaulichkeit der Faserbestandteile wurde in der Rangfolge Ca-S < TG < FPFS gesenkt. Gleichzeitig stieg die Futterpartikelpassage im Pansen durch TG- und FPFS-Zulagen tendenziell an, während die renale Allantoin-N-Ausscheidung unbeeinflußt blieb. Aus diesen Ergebnissen wird geschlossen, daß sich Veränderungen in der mikrobiellen Populationszusammensetzung des Pansens in gleicher Weise wie in den Simulationsversuchen eingestellt haben. Die verwendeten Ca-verseiften Fettsäuren waren unter den RUSITEC-Inkubationsbedingungen trotz mehrtägiger Adaptationsperioden nicht stabil, ihre Stabilität im Pansen nahm jedoch zu, wenn die Tiere zuvor über mehrere Tage mit Ca-verseiften Fettsäuren gefüttert worden waren. Ob es sich hierbei um eine Besonderheit der eigens für diese Untersuchungen hergestellten Ca-Seife oder um ein generelles Problem beim Einsatz von Ca-verseiften Fettsäuren in der Wiederkäuerfütterung handelte, muß weiter geprüft werden. 相似文献
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