635 research outputs found
Ombrotrophic Peat Bogs Are Not Suited as Natural Archives To Investigate the Historical Atmospheric Deposition of Perfluoroalkyl Substances
No full textAs ombrotrophic peat bogs receive only atmospheric input of contaminants, they have been identified as suitable natural archives for investigating historical depositions of airborne pollutants. To elucidate their suitability for determining the historical atmospheric contamination with perfluoroalkyl substances (PFAS), two peat cores were sampled at Mer Bleue, a bog located close to Ottawa, Canada. Peat cores were segmented, dried, and analyzed in duplicate for 25 PFASs (5 perfluororalkyl sulfonates (PFSAs), 13 perfluoroalkyl carboxylates (PFCAs), 7 perfluororalkyl sulfonamido substances). Peat samples were extracted by ultrasonication, cleaned up using a QuEChERS method, and PFASs were measured by HPLC-MS/MS. Twelve PFCAs and PFSAs were detected regularly in peat samples with perfluorooctane sulfonate (85-655 ng kg-1), perfluorooctanoate (150-390 ng kg-1), and perfluorononanoate (45-320 ng kg-1) at highest concentrations. Because of post depositional relocation processes within the peat cores, true or unbiased deposition fluxes (i.e., not affected by post depositional changes) could not be calculated. Apparent or biased deposition rates (i.e., affected by post depositional changes) were lower than measured/calculated deposition rates for similar urban or near-urban sites. Compared to PFAS production, PFAS concentration and deposition maxima were shifted about 30 years toward the past and some analytes were detected even in the oldest segments from the beginning of the 20th century. This was attributed to PFAS mobility in the peat profile. Considerable differences were observed between both peat cores and different PFASs. Overall, this study demonstrates that ombrotrophic bogs are not suited natural archives to provide authentic and reliable temporal trend data of historical atmospheric PFAS deposition. © 2012 American Chemical Society
Particle-size distribution of airborne poly- and perfluorinated alkyl substances
No full textEleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS-MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (<0.14. μm), maximum PFOS mass fractions were observed in the coarser size fractions between 1.38 and 3.81. μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively.Eleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS–MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (<0.14 μm), maximum PFOS mass fractions were observed in the coarser size fractions between 1.38 and 3.81 μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively
Perfluorinated compounds in marine surface waters: data from the Baltic Sea and methodological challenges for future studies
No full text
Environmental context.Perfluorinated compounds are man-made chemicals of emerging environmental concern because of their global distribution in water, air and biota. We investigate the distribution of these chemicals in surface water of the Baltic Sea, a unique ecosystem and the world’s largest body of brackish water. The observed contamination was of the same order of magnitude as classical persistent organic pollutants in the world’s oceans, and decreased with lower population density in the Baltic Sea catchments.
Abstract.Poly- and perfluorinated compounds (PFCs) are chemicals of emerging environmental concern. Except for very few coastal sites, PFC contamination of the Baltic Sea has not been investigated. In order to assess the PFC contamination of Baltic Sea water and evaluate the spatial distribution of PFCs, 74 surface water samples from the entire Baltic Sea were taken during two sampling campaigns in the summer of 2008 and analysed for PFCs. Of 40 analysed PFCs, 13 were detected at concentrations below 1 ng L–1, which indicates a rather low PFC contamination of Baltic Sea surface water. Usually, PFOA was the analyte observed in highest concentrations followed by PFNA, PFBS, and PFOS. PFC concentrations decreased from the Kattegat to the Bothnian Bay and the Gulf of Finland, reflecting the decreasing population density and thus the potential contamination in corresponding catchments or the decreasing influence of potentially contaminated North Sea water.
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Forms of the Intangible:Carl Th. Dreyer and the Concept of 'Transcendental Style'<em/>
No full textUdgivelsesdato: 2008The book Transcendental Style in Film, written in 1972 by future film director Paul Schrader, offers perhaps the most extensive analysis of how a particular film style might have a specifically religious significance. The article provides a critical discussion of Schrader’s theory, with a particular focus on the films of Carl Th. Dreyer. Schrader’s ideas are compared to alternative explanations of the same stylistic features provided by David Bordwell and Torben Grodal. The article concludes that while Schrader identifies a number of pertinent stylistic features, the ‘transcendental film’ is better understood as a subset of the art film mode. Torben Grodal’s description of the intertwined effect of a salient (often abstract) style and thematic content indicative of higher meaning, coupled with the contribution of a suitably disposed spectator, is, the article argues, more plausible than Schrader’s analysis.<br/
Hegemoni og videnskab
No full textArtiklen diskuterer "mikrofundamentalismens" hegemoni indenfor økonomisk videnskab og rejser spørgsmålet hvad det vil sige at bringe det tilophør. Jeg argumenterer for at overgangen fra et forskningsprogram som fx fra mikrofundamentalisme til keynesianisme ikke er et spørgsmål om at få hegemoniske forhold til at forsvinde, men derimod et spørgsmål om at erstatte et hegemoni med et andet
Review: Doing educational research : a guide for first time researchers
No full textTitle: Doing Educational Research : a guide for first time researchers
Author/Editor: Clive Opie
Publisher: Sage Publications
Publication Date: 2004
ISBN: Paperback 0761970029
Price: £18.99
Reviewed by: Torben Steeg, Independent D&T Consultan
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