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- Ferrow, Embaie, et al.
(författare)
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Multiproxy analysis of a new terrestrial and a marine Cretaceous-Paleogene (K-Pg) boundary site from New Zealand
- 2011
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 75:2, s. 657-672
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Tidskriftsartikel (refereegranskat)abstract
- An integrated study of palynology, Mossbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K-Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K-Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K-Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mossbauer spectroscopy shows an anomaly of Fe-containing particles in both K-Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic Os-187/Os-188 values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mossbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods. (C) 2010 Elsevier Ltd. All rights reserved.
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| 2. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Anthropogenic Forcings on the Surficial Osmium Cycle
- 2010
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:3, s. 881-887
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Tidskriftsartikel (refereegranskat)abstract
- Osmium is among the least abundant elements in the Earth's continental crust. Recent anthropogenic Os contamination of the environment from mining and smelting activities, automotive catalytic converter use, and hospital discharges has been documented. Here we present evidence for anthropogenic overprinting of the natural Os cycle using a ca. 7000-year record of atmospheric Os deposition and isotopic composition from an ombrotrophic peat bog in NW Spain. Preanthropogenic Os accumulation in this area is 0.10 +/- 0.04 ng m(-2) y(-1). The oldest strata showing human influence correspond to early metal mining and processing on the Iberian Peninsula (ca. 4700-2500 cal. BP). Elevated Os accumulation rates are found thereafter with a local maximum of 1.1 ng m(-2) y(-1) during the Roman occupation of the Iberian Peninsula (ca. 1930 cal. BP)and a further increase starting in 1750 AD with Os accumulation reaching 30 ng m(-2) y(-1) in the most recent samples. Osmium isotopic composition (Os-187/Os-188) indicates that recent elevated Os accumulation results from increased input of unradiogenic Os from industrial and automotive sources as well as from enhanced deposition of radiogenic Os through increased fossil fuel combustion and soil erosion. We posit that the rapid increase in catalyst-equipped vehicles, increased fossil fuel combustion, and changes in land-use make the changes observed in NW Spain globally relevant.
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| 7. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Platinum group elements in airborne particles in Mexico City
- 2006
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Ingår i: Environmental Science & Technology. ; 40:24, s. 7554 -7560
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Tidskriftsartikel (refereegranskat)abstract
- Automobile exhaust catalysts using platinum group elements (PGE) have been mandatory on new cars in the Mexico City Metropolitan Area (MCMA) since 1991. Platinum, Pd, Rh, Ir, and Os concentrations and the isotopic composition of Os were determined in PM10 samples from the MCMA. Samples were prepared by isotope dilution NiS fire assay, and analysis was performed by magnetic sector ICP-MS using a single collector instrument for Pt, Pd, Rh, and Ir analysis and a multicollector instrument for Os analysis. Pt, Pd, and Rh concentrations at a downtown location (Merced) increased from 1.7 pg of Pt m-3, 2.7 (4.0) pg of Pd m-3, and 1.2 ± 0.9 pg of Rh m-3 in 1991 to 9.6 ± 1.8 pg of Pt m-3, 10.2 ± 1.8 pg of Pd m-3, and 2.8 ± 0.6 pg of Rh m-3 in 2003. Concentrations at five sites in MCMA in 2003 averaged 9.3 ± 1.9 pg of Pt m-3, 11 ± 4 pg of Pd m-3, and 3.2 ± 1.0 pg of Rh m-3. In contrast, Ir and Os concentrations and Os isotopic composition remained relatively constant and were 0.08 ± 0.04 pg of Ir m-3, 0.030 ± 0.007 pg of Os m-3, and 0.60 ± 0.04, respectively, in the MCMA in 2003. Elevated Pt, Pd, and Rh concentrations in the MCMA are attributed to automobile catalysts. A Pt-Pd-Rh concentration peak in 1993 suggests that early catalysts emitted a larger amount of PGE, possibly due to factors inherent in the technology or the use of inappropriate gasoline. Therefore, this study suggests that the current introduction of automobile catalysts in developing countries may result in elevated PGE concentrations if it is not accompanied by infrastructures and policy measures supporting their efficient use.
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| 8. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Recent changes in platinum group element concentrations and osmium isotopic composition in sediments from an unrban lake
- 2004
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Ingår i: Environmental Science & Technology. ; 38, s. 396-402
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Tidskriftsartikel (refereegranskat)abstract
- Automobile catalyst emissions have resulted in the occurrence of elevated Pt, Pd, and Rh concentration in the urban and roadside environment. We investigate the chronology of platinum group elements (PGE) accumulation in dated sediments from an urban lake near Boston, MA. Chronological profiles demonstrate that Pt, Pd, and Rh concentrations increased following the introduction in catalysts with accumulation rates 6-16 times larger in 1992-2002 than prior to the introduction of catalysts. Ratios of these elements closely match their ratios in catalysts, providing further evidence of an automobile source. Iridium and Ru accumulation in sediments also increased following the introduction of catalysts, and while past Os contamination is associated with leather tanning, recent changes in the isotopic composition of Os indicate another anthropogenic source for this element. The PGE have similar geochemical properties and are difficult to separate from one another, and therefore, we suggest that automobile catalyst emissions also result in increasing environmental concentrations of Ir, Ru, and Os, which occur as impurities in catalysts. An automobile catalyst source of Ir and Os is supported by elevated concentrations of these elements in a tunnel dust sample.
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| 10. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Source characterisation of atmospheric platinum group element deposition into an ombrotrophic peat bog
- 2004
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0333 .- 1464-0325. ; 6:4, s. 335-343
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Tidskriftsartikel (refereegranskat)abstract
- Platinum, palladium, rhodium, iridium and osmium were found to be enriched relative to their expected natural concentrations in peat samples from Thoreau's Bog, an ombrotrophic peat bog in Concord, Massachusetts. The source of osmium into the bog was determined from its isotopic composition (187Os/188Os). Osmium is composed of 4% lithogenic osmium from atmospheric soil dust, 41% of anthropogenic osmium and 55% of osmium from a non-lithogenic, non anthropogenic source, with rain being a likely candidate for the latter. Significant anthropogenic and rain contributions are also expected for iridium. In contrast, platinum, palladium and rhodium are almost exclusively anthropogenic. The larger enrichments of platinum, palladium and rhodium indicate that automobile catalysts are the source of platinum group elements to Thoreau's bog. The bog is located approximately 300 m from a major road and, therefore, the occurrence of platinum elements is evidence for regional dispersion of these metals. The absence of a clear trend following the introduction of catalysts indicates that platinum group elements are not quantitatively conserved in peat with downward leaching and plants playing an important role in the accumulation of platinum group elements.
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