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- IDMS (7)
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- Copper (1)
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- Determination of metrology of new cadmium atomic weight (1)
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- Hypholoma fasciculare (1)
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- S K-edge X-ray absorption near edge spectroscopy (XANES) (1)
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- Wood decomposing basidiomycetes (1)
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- XRF (1)
- Zinc (1)
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Eingeladener Vortrag
- nein (3)
Messtechnik
(2002)
The neutron transmutation doping (NTD) of highly pure copper with zinc was investigated as a promising means of achieving controlled gradation of the zinc content in the range 1-20 wg g-1. The doping process leads to the enrichment of two stable isotopes 64Zn and 66Zn in a ratio which differs from that of natural isotopic distribution. Mass spectrometric investigations by thermal ionization mass spectrometry (TIMS) were performed to validate the results obtained by gamma spectrometry. The investigations included both determination of the isotopic ratios of the doped zinc isotopes and the analysis of the accumulated zinc contents by isotope dilution (ID) analysis. Thereby a sample-specific correction of the blank could be performed because the isotope 68Zn was not influenced, because of the transmutation process. The results obtained by TIMS prove the strict proportionality of the doped zinc content, in the range 5 to 20 wg g-1, to the neutron fluence. Comparison with gamma spectrometric results showed a very good agreement within the uncertainties.
A layer of Sb atoms, implanted with an energy of 400 keV and a nominal dose of 5×1016 atoms/cm2 into a high purity silicon wafer, was certified for its areal density (atoms/cm2) using Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA) and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and for its isotope ratio using INAA and ICP-IDMS. Excellent agreement between the results of the different independent methods was found. In the present work, the measurements of the homogeneity of the areal density of Sb, previously determined with RBS in spots having 1 mm diameter, are improved with synchrotron X-ray fluorescence analysis: Higher precision in even smaller sample spots allows to estimate a reduced inhomogeneity of the whole batch of samples of the order of only 0.4%. Thus the uncertainty of the certified value can further be reduced. Down to fractions of a chip with 0.3×0.4 mm2 area, the areal density is now certified as (4.81±0.06)×1016 Sb atoms/cm2, where the expanded uncertainty 0.06 (coverage factor k=2) corresponds to only 1.2%. The relative merits of the different analytical methods are discussed.
Nitrogen sources of oligoporus placenta and trametes versicolor evaluated in a 2³ experimental plan
(2012)
Four full-factorial 2³ experimental plans were applied to evaluate the nitrogen (N) sources of Oligoporus placenta and Trametes versicolor and their interaction with the atmospheric N2-assimilating bacterium Beijerinckia acida. The effects of N from peptone, of sapwood and of N from gaseous N2 on fungal, bacterial and fungal–bacterial activity were investigated. The activities were determined by quantification of biomass, formation of CO2, consumption of O2 and laccase activity. The significance of each effect was tested according to t-test recommendation.
The activity of both fungi was enhanced by peptone rather than sapwood or gaseous N2. Nevertheless, comparative studies under an N2-free gas mixture as well as under air revealed that the presence of N2 affected bacterial growth and bacterial–fungal cocultivations. Elemental analysis isotope ratio mass spectrometry (IRMS) of the bacterial and fungal biomass enabled estimation of N transfer and underlined gaseous N2 as requisite for fungal–bacterial interactions. Combining full-factorial experimental plans with an analytical set-up comprising gas chromatography, IRMS and enzymatic activity allowed synergistic effects to be revealed, fungal N sources to be traced, and symbiotic fungal–bacterial interactions to be investigated.
The main wood degraders in aerobic terrestrial ecosystems belong to the white- and brown-rot fungi, where their biomass can be created on wood decay only. However, total sulfur (S) concentration in wood is very low and only little is known about the different sulfur compounds in wood today. Sulfur-starved brown-rot fungi Gloeophyllum trabeum and Oligoporus placenta were incubated on sterilized pine wood blocks whereas Lentinus cyathiformis and the white-rot fungi Trametes versicolor were incubated on sterilized beech wood blocks. After 19 weeks of incubation, the S oxidation status was analyzed in wood, in degraded wood, and in biomass of wood-degrading fungi by synchrotron based S K-edge XANES, and total S and sulfate were quantified. Total sulfur and sulfate content in pine wood blocks were approximately 50 and 1 µg g-1, respectively, while in beech wood approximately 100 and 20 µg g-1 were found, respectively. Sulfur in beech was dominated by sulfate-esters. In contrast, pine wood also contained larger amounts of reduced S. Three out of four selected fungi caused a reduction of the S oxidation state in wood from oxidized S (sulfate-ester, sulfate) to intermediate S (sulfonate, sulfoxide) or reduced S (thiols, e.g., proteins, peptides, enzyme cofactors). Only O. placenta shifted thiol to sulfonate. Growth experiments of these fungi on selective minimal media showed that in particular cysteine (thiol), sulfonates, and sulfate enhanced total mycelium growth. Consequently, wood-degrading fungi were able to utilize a large variety of different wood S sources for growth but preferentially transformed in vivo sulfate-esters and thiol into biomass structures.
The phosphorylation of p-tert-butylcalix[8]arene (1) with phosphorus pentachloride and hydrolysis gives intramolecular bridging tert-butylcalix[8]arene triphosphates. The reactivity (esterification, dehydratisation, complexation), the structure (nmr and x-ray), and the stereochemical behaviour of the phosphates will be discussed.
The white-rot fungus Hypholoma fasciculare coexists with a bacterial community that uses low-molecular weight carbon sources provided by fungal, extracellular enzyme activities. Since fungal development on wood is limited by the availability of nitrogen (N), bacteria could contribute to the N supply. To prove or disapprove an interaction in terms of N transfer, N sources of the fungus and the coexisting bacterial isolates were investigated, and the bacterial N2 fixation was quantified. Fungal, fungal—bacterial and bacterial wood decomposition was analysed by Fourier transform infrared spectroscopy (FTIR), mass loss and surface pH. Microbial N preferences were investigated by elemental analysis isotope ratio mass spectrometry (IRMS). In addition, diazotrophic activity was explored after cultivation under a 15N2/O2 atmosphere. Decomposition was similar with and without bacteria and both H. fasciculare and coexisting bacteria preferred reduced N species, such as urea, ammonium and organic N. In most of the bacteria, the 15N abundance in the biomass increased significantly but to a low extent if they were cultivated under a 15N2/O2 atmosphere. This effect is considered an artefact and attributed to adsorption rather than to bacterial N2 fixation activity. Hence, the bacteria coexisting with H. fasciculare rather competed for the same N sources than supported fungal N supply by diazotrophic activity.
Zur Umsetzung der Verwaltungsvereinbarung der OFD Hannover und der Bundesanstalt für Materialforschung und -prüfung (BAM) über "Anerkennung und Überwachung von Prüflaboratorien im Rahmen von Erkundung und Bewertung kontaminierter Flächen" (15. Sept. 1995) wurde eigens ein "Arbeitskreis Anerkennungsgrundlagen Altlasten" einberufen, dem neben der BAM und der OFD Hannover die am Verfahren beteiligten Akkreditierungsgesellschaften DACH, DAP und DASMIN, die Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), das Umweltbundesamt (UBA), die Landesgewerbeanstalt Bayern (LGA), der TÜV Hannover/Sachsen-Anhalt und der Verband Deutscher Umweltlaboratorien sowie vereidigte Sachverständige und private Prüflaboratorien angehörten. Aufgabe dieses Arbeitskreises war es, "Anforderungen an Untersuchungsmethoden zur Erkundung und Bewertung kontaminationsverdächtiger/kontaminierter Flächen und Standorte auf Bundesliegenschaften" als Grundlage der Kompetenzbestätigungsverfahren zu erarbeiten. Mit Stand Februar 1997 wurden diese veröffentlicht (OFD-H/BAM Anforderungskatalog 02/97), im Juni 1998 aktualisiert und auf der Umwelt-CO-ROM des Bundesministeriums für Raumordnung, Bau- und Wohnungswesen (BMBau) als Anhang 2.5 der "Arbeitshilfen Altlasten" bekanntgemacht.
Mit dem Erlass des BMBau vom 07.11.1995 wurden alle Bau- und Vermögensabteilungen der Oberfinanzdirektionen angewiesen, Aufträge zur Untersuchung kontaminationsverdächtiger/kontaminierter Flächen (KVF/KF) nur noch an Unternehmen zu vergeben, die nach diesem Verfahren anerkannt sind.
Die oben genannten Anforderungen wurden 1998 bei der Formulierung des Anhanges 1 ("Anforderungen an die Probennahme, Analytik und Qualitätssicherung bei der Untersuchung") der Bundes-Bodenschutz- und Altlastenverordnung (BBodSchV) berücksichtigt. Mit Inkraftsetzung des Bundes-Bodenschutzgesetzes (BBodSchG) am 17.03.1998 und der BBodSchV am 12.07.1999 liegen nunmehr bundeseinheitliche gesetzliche Regelungen vor, die bei Bodenuntersuchungen sowie bei der Bearbeitung von Verdachtsflächen anzuwenden sind.
Da der Anhang 1 der BBodSchV aber nicht allein für den Zuständigkeitsbereich des Bundesministeriums für Verkehr, Bau- und Wohnungswesen (BMVBW) formuliert wurde, ergibt sich hier zur Vereinfachung und Vereinheitlichung des Vollzugs auf Liegenschaften des Bundes der Bedarf nach inhaltlichen Erläuterungen und Ergänzungen. Daher wurde gemeinsam von der BAM und der OFD Hannover im Rahmen der Neufassung ihrer "Verwaltungsvereinbarung zur Weiterentwicklung der wissenschaftlichen Grundlagen für die Akkreditierung und Überwachung von Prüflaboratorien/lngenieurbüros im Rahmen der Erkundung kontaminationsverdächtiger/kontaminierter Flächen auf Bundesliegenschaften und zur Durchführung von Eignungsprüfungen in der chemischen Analytik" vom 17.05.2000 die nachfolgende Neufassung "Anforderungen an Probennahme, Probenvorbehandlung und chemische Untersuchungsmethoden auf Bundesliegenschaften" erarbeitet. Diese ersetzt die Versionen vom Februar 1997 und Juni 1998. Voraussetzung für die Durchführung von Untersuchungen auf Bundesliegenschaften ist eine Akkreditierung auf der Grundlage dieser Anforderungen.
In der BBodSchV sind eine Reihe internationaler Normentwürfe aufgeführt, die nicht in jedem Fall im Detail dem aktuellen Diskussions- und Kenntnisstand entsprechen. In den überarbeiteten Anforderungen werden mit Hilfe von Hinweisen und Ergänzungen Präzisierungen vorgenommen und der aktuelle Stand dokumentiert.
Vom Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit (BMU) wurde gemäß Anhang 1 BBodSchV ein Fachbeirat "Verfahren und Methoden für Bodenuntersuchungen (FBU)" eingerichtet, dem auch Mitarbeiter der BAM und der OFD Hannover angehören. Eine zentrale Aufgabe dieses Fachbeirates ist die Zusammenstellung und Bekanntgabe aktueller Methoden und Verfahren. Diese durch das Umweltbundesamt (UBA) vorgesehenen Veröffentlichungen sind zu beachten.
Da die wesentlichen Anforderungen im Anhang 1 der BBodSchV enthalten sind, wurde zur Verbesserung der Übersichtlichkeit der Verordnungstext im folgenden wörtlich übernommen. Er ist durch Kursivdruck hervorgehoben. Teil 6 der vorliegenden Anforderungen ist in Abweichung von der BBodSchV zunächst in Normen und anschließend in Technische Regeln und sonstige Methoden gegliedert.
Isotope ratio mass spectrometry (IRMS) is an advanced method to investigate carbon (C) and nitrogen (N) in organic samples. In particular, the N content, its isotope signature and the C/N ratio reveal important facts of nutrient cycling, niche separation and ecological food webs. In this study, the characteristics of N turnover of wood decomposing microorganisms were investigated.
The growth of the white rot causing basidiomycete Trametes versicolor is enhanced after addition of ammonia or urea, whereas the brown rot causing Oligoporus placenta is not accelerated. In addition, an interaction of each fungus with atmospheric N2 assimilating (diazotrophic) bacteria was investigated. Cultivation experiments with a gas mixture of 15N2/O2 and subsequent IRMS analysis of dry biomass of the diazotrophs Azotobacter croococcum, Beijerinckia acida and Novosphingobium nitrogenifigens revealed that they assimilated up to 12% of their N from N2. The experiments reflected N availability as a prerequisite for efficient growth of decomposing basidiomycetes and diazotrophs. Fungal–bacterial co-cultivation experiments showed that depending on the growth characteristics and bacterial N2 assimilation activity N is transferred from certain bacteria into fungal biomass. Thus, the experiments gave a first indication of an interaction between wood decomposing basidiomycetes and diazotrophs, which is a novel pathway of fungal N acquisition.
Boron isotope compositions of crop plants: A new tracer for the origin and authenticity of food
(2009)
Seabird excrements (guano) have been preserved in the arid climate of Northern Chile since at least the Pliocene. The deposits of marine organic material in coastal areas potentially open a window into the present and past composition of the coastal ocean and its food web. We use the stable isotope composition of nitrogen and carbon as well as element contents to compare the principal prey of the birds, the Peruvian anchovy, with the composition of modern guano. We also investigate the impact of diagenetic changes on the isotopic composition and elemental contents of the pure ornithogenic sediments, starting with modern stratified deposits and extending to fossil guano. Where possible, 14C systematics is used for age information. The nitrogen and carbon isotopic composition of the marine prey (Peruvian anchovy) of the birds is complex as it shows strong systematic variations with latitude. The detailed study of a modern profile that represents a few years of guano deposition up to present reveals systematic changes in nitrogen and carbon isotopic composition towards heavier values that increase with age, i.e. depth. Only the uppermost, youngest layers of modern guano show compositional affinity to the prey of the birds. In the profile, the simultaneous loss of nitrogen and carbon occurs by degassing, and non-volatile elements like phosphorous and calcium are passively enriched in the residual guano. Fossil guano deposits are very low in nitrogen and low in carbon contents, and show very heavy nitrogen isotopic compositions. One result of the study is that the use of guano for tracing nitrogen and carbon isotopic and elemental composition in the marine food web of the birds is restricted to fresh material. Despite systematic changes during diagenesis, there is little promise to retrieve reliable values of marine nitrogen and carbon signatures from older guano. However, the changes in isotopic composition from primary marine nitrogen isotopic signatures towards very heavy values generate a compositionally unique material. These compositions trace the presence of guano in natural ecosystems and its use as fertilizer in present and past agriculture.
The quantitative analysis of toxic metals in plastics is very important for different sectors of industry and daily life. Many routine procedures have been established based on X-ray fluorescence or inductively coupled plasma atomic emission spectrometry. However, all of them require suitable reference materials to calibrate or validate. These reference materials ideally are being certified by reference procedures. The development of such reference procedures for sulfur and the four toxic elements cadmium, chromium, mercury and lead in plastics is described here. The procedures are based on double isotope dilution mass spectrometry including analyte–matrix separation. The applied mass spectrometric techniques are thermal ionization mass spectrometry as well as inductively coupled plasma mass spectrometry. Memory effects of mercury and dissolution of chromium(III) oxide have been considered especially. The expanded uncertainties have been improved from the percent range down to the per mill range during the development of the procedure from the early analysis of BCR-680/681 to the recent analysis of CCQM-P106. With the fully developed procedures expanded uncertainties (k = 2) between 0.1 and 0.4% for cadmium, chromium, lead and sulfur and around 1% for mercury can be achieved. The so developed procedures have been successfully applied to the certification of reference materials as well as to intercomparisons organized by CCQM.
A modified Pb–matrix separation procedure using NH4HCO3 solution as eluent has been developed and validated for determination of Pb isotope amount ratios by thermal ionization mass spectrometry. The procedure is based on chromatographic separation using the Pb·Spec resin and an in-house-prepared NH4HCO3 solution serving as eluent. The advantages of this eluent are low Pb blanks (<40 pgmL-1) and the property that NH4HCO3 can be easily removed by use of a heating step (>60 °C). Pb recovery is >95 % for water samples. For archaeological silver samples, however, the Pb recovery is reduced to approximately 50 %, but causes no bias in the determination of Pb isotope amount ratios. The validated procedure was used to determine lead isotope amount ratios in Trojan silver artefacts with expanded uncertainties (k=2) <0.09 %.
Isotope reference materials are essential to enable reliable and comparable isotope data. This article reviews the work in this field within the past years. The focus is on all stable elements, except for classical stable isotopes (H, C, N, O, S) and for radioactive elements. Currently available isotope reference materials are listed. The limitations of synthetic isotope mixtures being used to characterize these materials are discussed, as well as the limitations of the isotope reference materials, such as uncertainty and homogeneity. The needs for present research on isotope variations are being considered and are compared to the limitations of current isotope reference materials. This disagreement between both can only be solved by providing isotope reference materials defining a δ-scale for each element of interest. Such materials should be provided with additional data on isotope abundances whenever possible. As an outlook a possible outline for a new program on isotope reference materials is discussed.