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- Holmstrand, H., et al.
(författare)
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Origin of PCDDs in ball clay assessed with compound-specific chlorine isotope analysis and radiocarbon dating.
- 2006
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 40:12, s. 3730-5
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated dibenzo-p-dioxins (PCDDs) of high concentrations in a ball clay deposit from the Mississippi Embayment were found to be consistent with a natural abiotic and non-pyrogenic origin by investigation with bulk radiocarbon analysis, compound-specific chlorine isotope analysis (CSIA-delta37Cl) of octachlorodibenzo-p-dioxin (OCDD), and black carbon (BC) analysis. The conventional radiocarbon date of total organic carbon from a depth of approximately 10 m in three parallel cores ranged from 14 700 years to >48 000 years, indicating that the strata with elevated levels of PCDDs have remained isolated from recent anthropogenic input in these >40 Ma old clay sediments. The CSIA-delta37Cl of OCDD yielded a delta37Cl of -0.2 per thousandth, which is significantly higher than the postulated range for biotic chlorination by chloroperoxidase enzymes, -11 to -10 per thousandth, and falls within the known range for abiotic organochlorines, -6 to +3 per thousandth. The absence of correlations between concentrations of PCDDs and corresponding pyrogenic black carbon (BC), together with estimations of BC sorptive loadings and the absence of polychlorinated dibenzofurans (PCDFs), suggest that vegetation fires did not form these ball-clay PCDDs. Results from this study indicate that the high levels of the toxic and carcinogenic PCDDs found in kaolinite-bearing clays may result from natural abiotic formation via in situ surface-promoted reactions on the clay mineral, including a so-far unknown organic precursor, rather than being the result of anthropogenic contamination.
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- Teuten, Emma L., et al.
(författare)
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Spectral characterization of two bioaccumulated methoxylated polybrominated diphenyl ethers
- 2006
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 62:2, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- Two methoxylated polybrominated diphenyl ethers (MeO-PBDEs) were isolated from a True’s beaked whale (Mesoplodon mirus) and identified by NMR (1H, 1H–1H and 1H–13C) and high resolution mass spectrometry as 2-(2′,4′-dibromophenoxy)-3,5-dibromoanisole (6-MeO-BDE47) and 2-(2′,4′-dibromophenoxy)-4,6-dibromoanisole (2′-MeO-BDE68). Previously the structures of these bioaccumulated compounds have been determined by comparison of their mass spectra and gas chromatographic (GC) retention times with those of authentic standards. While this method is accepted and generally successful, NMR of the isolated compounds allows us to definitively identify the congeners. Our characterizations are consistent with those made for MeO-PBDEs in other organisms, identified by chromatographic methods.
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