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Active mud volcanoes on the upper slope of the western Nile deep-sea fan—first results from the P362/2 cruise of R/V Poseidon 总被引：1，自引：0，他引：1
Tomas Feseker Kevin R. Brown Cecile Blanchet Florian Scholz Marianne Nuzzo Anja Reitz Mark Schmidt Christian Hensen 《Geo-Marine Letters》2010,30(3-4):169-186
In February 2008, cruise P362/2 was undertaken aboard R/V Poseidon to the Giza and North Alex mud volcanoes (MVs) on the upper slope of the western Nile deep-sea fan. Emitted fluids were strongly depleted in chloride and rich in hydrocarbons, predominantly of thermogenic origin. In-situ sediment temperature measurements indicate extremely high and moderate levels of activity for the North Alex MV and Giza MV, respectively, and suggest rapid changes from dormant to active stages. Both the physical properties of core sediments (e.g., color and magnetic susceptibility), and their assemblages of micro- and nannofossils point to different sources for the two mud volcanoes. Biostratigraphic dating suggests source depths of 2,100–2,450 mbsf for the Giza MV and 1,150–1,550 mbsf for the North Alex MV. Very high temperatures of up to 70°C in shallow sediments at the North Alex MV can be explained only if the fluid source were warmer and deeper than the sediment source. 相似文献
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Xanthates are used in the flotation of sulfide ores although their aqueous solutions are not stable under certain conditions. Their stability in acidic and weakly acidic aqueous solutions was therefore investigated, as these media are required for some processes.The peak absorbances of ethylxanthate ion and carbon disulfide were first determined in aqueous solution. The decomposition of ethylxanthate ion was analyzed by measuring variations in absorbance (at 301 nm) and pH with respect to time. A pH regulation system was then used while measuring variations in absorbance and productions of protons caused by xanthate decomposition.The results concerning xanthate half-lives show good agreement with the literature, but the kinetic results deviate substantially. The following relation was obtained for half-life: We established that ethylxanthate decomposition at pH 4 is a first order reaction with respect to ethylxanthate concentration, and postulating this order to the other pH values, the following kinetic relation was found: where v is the rate of decomposition (mol l?1 min?1), and [EtX?]∞ is the ethylxanthate concentration when the decomposition equilibria are reached (mol l?1). The better concentration was found to obey the law: 相似文献
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Heng Xiao C. Roberto Mechoso Ruiyu Sun Jongil Han Hua-Lu Pan Sungsu Park Cecile Hannay Chris Bretherton Joao Teixeira 《Climate Dynamics》2014,43(3-4):737-752
We present a diagnostic analysis of the marine low cloud climatology simulated by two state-of-the-art coupled atmosphere–ocean models: the National Center for Atmospheric Research community earth system model version 1 (CESM1) and the National Center for Environmental Predictions global forecasting system-modular ocean model version 4 (GFS-MOM4) coupled model. In the CESM1, the coastal stratocumulus (Sc)-topped planetary boundary layers (PBLs) in the subtropical Eastern Pacific are well-simulated but the climatological transition from Sc to shallow cumulus (Cu) is too abrupt and occurs too close to the coast. By contrast, in the GFS-MOM4 the coastal Sc amount and PBL depth are severely underestimated while the transition from Sc to shallow Cu is “delayed” and offshore Sc cover is too extensive in the subtropical Eastern Pacific. We discuss the possible connections between these differences in the simulations and differences in the parameterizations of shallow convection and boundary layer turbulence in the two models. 相似文献
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Computer-assisted analyses of more than 600 radiocarbon-dated sea-level indicators from northwestern Europe, concentrated around the North Sea margin, indicate that vertical crustal movements are more important that eustatic sea-level change in determining the locus of Holocene shoreline positions through time. For the past 14,000 radiocarbon years, the divergence of sea-level data for the northwest European sectors exceeds the maximum estimated sea-level rise by a factor of two or more. Projecting these data to a single meridian demonstrates the remarkable variety of vertical crustal movement in northwestern Europe.Accumulating radiocarbon-dated sea-level indicators into millennial cohorts, we generate isobase maps which begin to specify areas of notable vertical crustal mobility. These isobase maps appear to confirm that eustatic sea-level rise is subordinate to postglacial geoidal excursions in determining the locus of contemporary northwestern European shorelines. 相似文献
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John A. Paquette Cecile Engrand Oliver Stenzel Martin Hilchenbach Jochen Kissel the COSIMA Team 《Meteoritics & planetary science》2016,51(7):1340-1352
The calcium‐aluminum‐rich inclusions (CAIs) found in chondritic meteorites are probably the oldest solar system solids, dating back to 4567.30 ± 0.16 million years ago. They are thought to have formed in the protosolar nebula within a few astronomical units of the Sun, and at a temperature of around 1300 K. The Stardust mission found evidence of CAI‐like material in samples recovered from comet Wild 2. The appearance of CAIs in comets, which are thought to be formed at lower temperatures and larger distances from the Sun, is only explicable if some mechanism allows the efficient transfer of such objects from the inner solar nebula to the outer solar nebula. Such mechanisms have been proposed such as an X‐wind or turbulence. In this work, particles collected from within the coma of comet 67P/Churyumov–Gerasimenko are examined for compositional evidence of the presence of CAIs. COSIMA (the Cometary Secondary Ion Mass Analyzer) uses secondary ion mass spectrometry to analyze the composition of cometary dust captured on metal targets. While CAIs can have a radius of centimeters, they are more typically a few hundred microns in size, and can be smaller than 1 μm, so it is conceivable that particles visible on COSIMA targets (ranging in size from about 10 μm to hundreds of microns) could contain CAIs. Using a peak fitting technique, the composition of a set of 13 particles was studied, looking for material rich in both calcium and aluminum. One such particle was found. 相似文献
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During 1998/1999, surface and subsurface sediment samples were collected along the entire length of the Spokane River from its outlet at the northern end of Lake Coeur d'Alene (CDA), Idaho, to Lake Roosevelt on the Columbia River, Washington. The study was conducted to determine if the trace element enrichments observed in Lake CDA and on the floodplain and in the CDA River extend through the Spokane River Basin (SRB). As in Lake CDA, surface sediments in the SRB are enriched in Pb, Zn, As, Cd, Sb and Hg relative to local background levels. Pb, Cd and Zn are the most elevated, with maximum enrichment occurring in the upper Spokane River in close proximity to Lake CDA. On average, enrichment decreases downstream, apparently reflecting both increased distance from the inferred source (the CDA River Basin), as well as increased dilution by locally derived but unenriched materials. Only Cd and Zn display marked enrichment throughout the SRB. Pb, Zn and Cd seem to be associated mainly with an operationally defined iron oxide phase, whereas the majority of the As and Sb seem to be matrix‐held. Subsurface sediments also are enriched in Pb, Zn, As, Cd, Sb and Hg relative to background levels. Based on 137Cs and excess 210Pb dating, trace element enrichment began in the middle part of the SRB (Long Lake) between 1900 and 1920. This is contemporaneous with similar enrichments observed in Lake CDA, as well as the completion of Long Lake Dam (1913). In the most downstream part of the basin (Spokane River Arm of Lake Roosevelt), enrichment began substantially later, between 1930 and 1940. The temporal difference in enrichment between Long Lake and the River Arm may reflect the latter's greater distance from the presumed source of the enrichment (the CDA River Basin); however, the difference is more likely the result of the completion of Grand Coulee Dam (1934–1941), which formed Lake Roosevelt, backed up the Spokane River, and increased water levels in the River Arm by about 30 m. 相似文献
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Given the public's limited knowledge of marine environments, informing the public about marine protection presents a unique challenge. Studies have shown a well-informed public is more likely to support environmental issues and that newspapers, in particular, are considered a credible media source. This research investigates media representations of current South Australian efforts to establish a marine protected area (MPA). Articles from five newspapers between 1999 and 2006 were examined for content in the following areas: local marine ecology, the policy process of MPA establishment and stakeholder views. The research found that newspapers concentrated their reporting on opposing stakeholders, opinions and were largely ineffective in conveying the significance of the local marine ecology, the economic benefits of the MPA, and the delayed establishment process. These information gaps have left the public poorly informed, and therefore, there is unlikely to be significant pressure to overcome the continued delays in the establishment process. 相似文献