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Eingeladener Vortrag
- nein (16)
Zur Sicherung von Deponien und Altlasten mit dem Ziel eines langfristig wirksamen Grundwasserschutzes werden seit Mitte der 80er Jahre Kombinationsdichtungen (Verbund aus Kunststoffdichtungsbahn und mineralischen Dichtschichten) eingesetzt. Um deren Langzeitbeständigkeit auch unter extremen Bedingungen bewerten zu können, wurden Permeationsmesszellen, welche die Verhältnisse in der Deponie nachstellen und über einen Zeitraum von 12 Jahren mit einem Mehrkomponentengemisch konzentrierter organischer Verbindungen beaufschlagt worden waren, zerlegt und die Auswirkungen der Schadstoffpermeation auf die Abdichtungsmaterialien untersucht. Schwerpunkte der hier vorgestellten Arbeiten waren Untersuchungen: - zur Auswirkung der Permeation des Gemisches an organischen Verbindungen auf die Eigenschaften der Kunststoffdichtungsbahn, - zur vertikalen Verteilung der organischen Verbindungen in den mineralischen Dichtungen, - zu Veränderungen mineralogischer, mikromorphologischer und bodenmechanischer Eigenschaften der mineralischen Dichtungsmaterialien, - zu mikrobiellen Aktivitäten in den mineralischen Dichtungen. Daneben wurden Stofftransportparameter bestimmt und eine Modellierung des Stofftransportes durchgeführt. Die verschiedenen untersuchten Materialien der Kombinationsdichtungen erwiesen sich unter den extremen Bedingungen als ein stabiles und effizientes Abdichtungssystem.
Vor-Ort-Untersuchungen - ein Beitrag für eine zuverlässige Bewertung kontaminierter Standorte
(1998)
Vor-Ort-Untersuchungen - ein Beitrag für eine zuverlässige Bewertung kontaminierter Standorte
(1998)
Herstellung eines Referenzmaterials zur Untersuchung der Eluierbarkeit organischer Schadstoffe
(2001)
Quality assurance is an essential requirement in many areas of soil testing. Soil sampling plays an important role in soil investigation. One important quality assurance measure is evidence of the competence of institutions offering sampling services (testing laboratories) to carry out appropriate sampling. A special quality assurance procedure has been developed in the course of the investigation and assessment of suspected and contaminated sites on federal property. Testing laboratories are granted official recognition by an independent competent institution, based on well-defined criteria with regard to testing methodology and the qualifications held by the personnel. A prerequisite for such recognition is an effective accreditation procedure. Currently only testing laboratories with recognised status are commissioned for work on contaminated sites on federal property.
Composite liners (a geomembrane in intimate contact with a mineral liner) are frequently used to line landfills and contaminated sites. It is therefore very important to characterise the behaviour of these systems even under extreme conditions.
An investigation was undertaken to determine the influence of a mixture of concentrated organic contaminants on composite liner materials taken from test cells that had been dismantled after a 12-year permeation test.
The organic hydrocarbons had permeated the HDPE-geomembrane and had then migrated or had been adsorbed within the mineral liners, depending on their properties. The obtained concentration profiles of the contaminant mixture components indicate that the various mineral layer materials have selective retardation abilities which correspond to the different parameters of the organic compounds as well as of the mineral layer.
In addition, contaminant transport in the composite liners tested was modelled and the results of the model analysis compared with measurement data. An example (acetone) illustrates the calculated spatial and temporal contaminant concentration.
The composite liners investigated exhibit a very good sealing capacity against the concentrated organic contaminants used.
Long term behaviour of composite liners under exposure to a mixture of concentrated hydrocarbons
(1999)
Methodical aspects of soil sampling regarding the requirements of the federal soil protection act
(2000)
The fabric of mineral liner materials that had been exposed to organic compounds over a 12-year period was investigated as part of a wider research project. Macromorphological and micromorphological changes in the fabric were identified using computed tomography and polarisation microscopy.
Special care was taken to ensure artefact free sampling and sample preparation, in particular, the drying method used, has a substantial influence on the quality of the thin sections.
Fabric changes due to contaminant permeation over several years are, by and large, relatively small and their intensity is material specific. Silty clay CML1, in particular, contains a somewhat greater number of fissures and voids in comparison with the original material. The superposition of various processes in both test procedures and sample preparation may lead to fabric changes which can impede interpretation of the results.
A thin-layer reference material for surface and near-surface analytical methods was produced and certified. The surface density of the implanted Sb layer was determined by Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA), and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) equipped with a multi-collector. The isotopic abundances of Sb (121Sb and 123Sb) were determined by multi-collector ICP-MS and INAA. ICP-IDMS measurements are discussed in detail in this paper. All methods produced values traceable to the SI and are accompanied by a complete uncertainty budget. The homogeneity of the material was measured with RBS. From these measurements the standard uncertainty due to possible inhomogeneities was estimated to be less than 0.78% for fractions of the area increments down to 0.75 mm2 in size. Excellent agreement between the results of the three different methods was found. For the surface density of implanted Sb atoms the unweighted mean value of the means of four data sets is 4.8121016 cm-2 with an expanded uncertainty (coverage factor k=2) of 0.0921016 cm-2. For the isotope amount ratio R (121Sb/123Sb) the unweighted mean value of the means of two data sets is 1.435 with an expanded uncertainty (coverage factor k=2) of 0.006.
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.
Volatile organic compounds (VOC) were investigated at a dry-cleaning facility of a former military site in Germany. VOCs have leaked into the unsaturated soil zone consisting of sandy aggragated material and fine to medium sand.
The groundwater table is located at 1.50 to 2.00 m.
The following investigations were performed:
·Soil sampling using an open window sampler, layer specific determination of VOC in the soil using gas chromatography after the following sample preparation procedure
- extraction with methanole
- extraction with pentane
- multiple headspace extraction (MHE) [1]
·Soil gas measurements, sampling using concentrating steps [2]
The various extraction procedures for VOC analysis in soil have yielded different
results. The results will be discussed with an emphasis on risk assessment, and recommendations for the procedure will be presented.
References
[1 ] DIN EN ISO 10301: 08.97: Wasserbeschaffenheit - Bestimmung leichtflüchtiger halogenierter Kohlenwasserstoffe - Gaschromatographische Verfahren
[2] VDI-Richtlinie 3865:06.98: Messen organischer Bodenverunreinigungen, Blatt 3: Gaschromatographische Bestimmung von niedrigsiedenden organischen Verbindungen in Bodenluft nach Anreicherung an Aktivkohle oder XAD-4 und Desorption mit organischen Lösungsmitteln