Separation of Clay Minerals from Host Sediments Using Cation Exchange Resins     

S.Ismael H.M.Baioumy 《中国地球化学学报》2003,22(4):337-344

Classic physical and chemical treatments applied to separating clay minerals from the host sediments are often difficult or aggressive for clay minerals. A technique using cation exchange resins (amberlite IRC-50H and amberlite IR-120) is used to separate clay minerals from the host sediments. The technique is based on the exchange of cations in the minerals that may be associated clay minerals in sediments, such as Ca and Mg from dolomite; Ca from calcite, gypsum and francolite with cations carried by resin radicals. The associated minerals such as gypsum, calcite, dolomite and francolite are removed in descending order. Separation of clay minerals using cation exchange resins is less aggressive than that by other classic treatments. The efficiency of amberlite IRC-50H in the removal of associated minerals is greater than that of amberlite IR-120.  相似文献   

Characterization of some Egyptian serpentinites used as ornamental stones   总被引：1，自引：0，他引：1  

I. S. Ismael  M. S. Hassan 《中国地球化学学报》2008,27(2):140-149

Egypt is characterized by wide occurrence of serpentinites, particularly in the central and southern parts of Eastern Desert. There are several cooperate factors that affect the serpentinites used as ornamental stones. These factors involve mineralogical characteristics （including mineral composition and microstructure parameter）, physical properties and mechanical properties. Antigorite is an essential serpentinite mineral, with a minor amount of chrysotile. Talc, carbonates （magnesite and dolomite） and tremolite are the main associated minerals. Quality and quantity of associated minerals such as talc and carbonates （dolomite and magnesite） affect the properties of serpentinites used as ornamental stones. Carbonates are resistant to weathering but suffer from acidic cleaning agents in interior use, whereas serpentinites with a high content of talc used on external faces undergo an increase in volume and a consequent rapid degradation. Studied serpentinites are characterized by relatively small grain size with foliated texture, low water absorption, low porosity, and high abrasion resistance. In the samples studied the uniaxial compressive strength （UCS） varies between 89 and 189 MPa, with an average of 152 MPa. According to the classification of Bell （1992）, sample No. B8 is very high in strength while the rest high in strength.  相似文献   

Influence of vibration grinding and calcination on the physico-chemical properties of Egyptian kaolinite     

I. S. Ismael  M. K. Abd El-Rahman  M. S. Hassan 《Mineralogy and Petrology》1999,67(1-2):45-57

Summary The effects of vibratory grinding and calcination on the structure and reactivity of Kalabsha kaolinite were studied by means of XRD, IR, DTA and surface area determination. Leaching experiments on ground and calcined samples were carried out using 20% HCl for aluminum extraction. At the early stages of grinding, partial destruction of stacked kaolinite layers occurred. These changes were associated with an increase in surface area due to formation of fine grains with numerous boundaries. Further grinding, as well as calcination, led to deterioration of the kaolinite structure. A significant increase of surface area was observed, starting from 18 m²/g for the original sample to a maximum of 42 m²/g after 120 minutes of grinding and 30 m²/g after calcination at 300°C. The extraction of aluminum after 30 minutes leaching time was about 97% for kaolinite ground for 240 minutes, and about 93% for kaolinite calcined at 550°C.

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Der Einfluß von Aufmahlen und Kalzinierung auf die physiko-chemischen Eigenschaften von ägyptischem Kaolinit

Zusammenfassung Die Effekte von Vibrations-Mahlung und Kalzinierung auf die Struktur und die Reaktivität von Kalolinit aus Kalabsha wurden mit XRD, IR, DTA und Methoden zur Bestimmung der Oberfläche untersucht. Auslaugungsexperimente zur Extraktion des Aluminiums erfolgten an gemahlenen und kalzinierten Proben unter Verwendung 20% er Salzsäure. In den Frühstadien des Mahlprozesses tritt eine teilweise Zerstörung der Kaolinitschichtstruktur auf. Diese Änderungen gehen mit einer Zunahme der Oberfläche, infolge der Neubildung von Körnern mit zahlreichen Korngrenzen, einher. Weiteres Aufmahlen und Kalzinieren führt zu zusätzlicher Zerstörung der Kaolinitstruktur. Eine signifikante Zunahme der Oberfläche von 18 m²/g für das Ausgangsmaterial auf 42m²/g nach 120 min Aufmahlen, bzw. auf 30 m²/ g nach Kalzinierung bei 300°C ist zu beobachten. Die Extraktion von Aluminium nach 30 minütiger Auslaugung liegt bei 97% für gemahlenen Kaolinit (240 min) und bei 93% für bei 550°C kalzinierten Kaolinit.

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Effect of self-weight consolidation on a hydro-sedimentological model for the Río de la Plata estuary     

Pablo Santoro  Mónica Fossati  Pablo Tassi  Nicolas Huybrechts  Damien Pham Van Bang  Ismael Piedra-Cueva 《国际泥沙研究》2019,34(5):444-454

The effect of the consolidation process on the morphodynamics and fine sediment dynamics of the Río de la Plata estuary is explored through a circulation-wave-sediment transport model. The consolidation model is calibrated based on settling column experimental data. Different simulations are done in order to initialize the mud layer distribution and to investigate the impact of different erosion parameter assumptions on the modeled sediment dynamics. Finally a two-year simulation is done with and without the consolidation process and realistic hydrodynamic forcings. Considering the consolidation process, the model correctly reproduces measured vertical density profiles in the Montevideo Bay access channel. The simulated suspended sediment dynamics behavior in Montevideo Bay with the consolidation process provides a more realistic deposition pattern in regard to the dredging activities.  相似文献   

Seasonal variability of the Antarctic Coastal Current and its driving mechanisms in the Weddell Sea   总被引：2，自引：0，他引：2  

Ismael Núez-Riboni  Eberhard Fahrbach 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):1927-1941

Insight into the dynamics of the Antarctic Coastal Current (ACoC) is achieved by quantifying the contributions of its driving mechanisms to the seasonal variability of its barotropic and baroclinic components. These mechanisms are sought out in the local wind, the sea-ice concentration, wind curl of the Weddell Gyre (Sverdrup transport) and the thermohaline forcing related to warming/cooling and ice melting and freezing. These driving mechanisms induce most of the seasonal variability of both the barotropic and baroclinic components of the ACoC by deepening the pycnocline towards the coast and sharpening the baroclinic profile following thermal wind balance. The resulting coastal current has mainly a barotropic transport (82%) and a major annual cycle, which explains 37% of this component's variability (tides and other high-frequency events generate 40%). The wind contributes with 58% of the seasonal variability of the barotropic component and 23% of the baroclinic; the sea-ice concentration contributes with 8% and 18%, respectively; Sverdrup transport with 4% and 30% and the thermohaline forcing with 30% and 29%. The results of this study are obtained with analysis of fifteen CTD sections (potential density and geostrophic velocities) of RV-Polarstern obtained between 1992 and 2005, as well as composite, spectral and harmonic analyses of 9 years of time series from moored instruments (current speed and temperature), wind speed, atmospheric pressure and sea-ice concentration of satellite imagery.  相似文献   

Ontogenetic habitat use by mangrove/seagrass-associated coral reef fishes shows flexibility in time and space     

Ismael A. Kimirei  Ivan Nagelkerken  Ben Griffioen  Coen Wagner  Yunus D. Mgaya 《Estuarine, Coastal and Shelf Science》2011

Tropical shallow-water habitats such as mangroves and seagrass beds are widely acknowledged as important juvenile habitats for various coral reef fish species, most of which are commercially important to fisheries. Spatio-temporal variability in ontogenetic habitat use by fish among these tropical coastal ecosystems has rarely been investigated, yet there are sufficient reasons to believe that this plays an important role. In the present study, we test the spatio-temporal variability in patterns of ontogenetic habitat use by some mangrove/seagrass-associated coral reef fishes (Lethrinus harak, Lethrinus lentjan, Lutjanus fulviflamma and Siganus sutor). Abundances of these four species were investigated during two years in Tanzanian coastal waters, using underwater visual census in mangrove, seagrass, shallow and deep mudflat, and shallow and deep coral reef habitats. The study covered four distinct seasons of the year and was done at two spatially separated (>40 km) locations. Averaged across locations, seasons and years, juveniles (≤10 cm length) of the four study species had significantly higher relative densities in shallow-water (mangroves and seagrass beds) than in deep-water habitats (deep mudflats or coral reefs), whereas the opposite pattern was found for the adults (>15 cm). These findings suggest a strong and general pattern of ontogenetic habitat shifts from shallow- to deep-water habitats. However, specific habitat-use patterns of juveniles as well as adults differed significantly in time and space. Various species showed subtle to considerable flexibility in juvenile as well as adult habitat use across seasons, years, or at different locations. Furthermore, for some species the data suggest presence of ontogenetic habitat shifts at one location but lack thereof at the other location. In summary, ontogenetic habitat use needs to be considered at various spatial and temporal scales for the interpretation of habitat utilization by fish during different life stages. This is important for conservation and management of these habitats, as essential habitats or seasons may be ignored or over-emphasized with respect to their importance for fish during different parts of their life cycle.  相似文献   

The role of the deep mixing in the Storfjorden shelf water plume     

Anna Akimova  Ursula SchauerSergey Danilov  Ismael Núñez-Riboni 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):403-414

Hydrographic observations in deep Fram Strait evidence a plume of Storfjorden Brine-enriched Shelf Water in 1986, 1988 and 2002. The plume spreads along the continental slope over 600 km away from its formation area and reaches 2000 m depth. The plume is 30 to 80 m thick in the deep layer of Fram Strait; it is almost 0.4 °C warmer and 0.06 more saline than the ambient water. The velocity of the plume, observed by a moored current meter in Fram Strait, is 12.60±4.70 cm s⁻¹ .The hydrographic properties of the plume are used to study entrainment. A streamtube model with four entrainment parameterizations is applied. Two Froude-number dependent parameterizations lead to mixing mostly happening over the shelf break, where the Froude number is large. This is in agreement with the traditional view, but is inconsistent with the observed temperature and salinity of the Storfjorden plume. Therefore further entrainment assumptions (a constant and a volume-dependent entrainment) are tested. The volume-dependent entrainment scheme yields the best representation of entrainment in the Storfjorden plume. Our results emphasize the necessity of strong mixing in the deep layers in Fram Strait to achieve an agreement with observed properties of the plume.  相似文献   

Comparative paralytic shellfish toxin profiles in two marine bivalves during outbreaks of Gymnodinium catenatum (Dinophyceae) in the Gulf of California   总被引：1，自引：0，他引：1  

Gárate-Lizárraga I  Bustillos-Guzmán JJ  Alonso-Rodríguez R  Luckas B 《Marine pollution bulletin》2004,48(3-4):397-402

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Photometric redshifts in the SWIRE Survey     

Michael Rowan-Robinson  Tom Babbedge  Seb Oliver  Markos Trichas  Stefano Berta  Carol Lonsdale  Gene Smith  David Shupe  Jason Surace  Stephane Arnouts  Olivier Ilbert  Olivier Le Févre  Alejandro Afonso-Luis  Ismael Perez-Fournon  Evanthia Hatziminaoglou  Mari Polletta  Duncan Farrah  Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):697-714

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Geochemical study of submicron particulate matter(PM1)in a metropolitan area     

Ismael L.Schneider  Elba C.Teixeira  Guilherme L.Dotto  Diana Pinto  Cheng-Xue Yang  Luis F.O.Silva 《地学前缘(英文版)》2022,(1):417-429

Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization.In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization(PMF)in receptor modeling in the Metropolitan Area of Porto Alegre,Brazil.The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites.Major ion and trace element concentrations were assessed.The average concentrations were 12.8 and 15.2μg/m³ for Canoas and Sapucaia do Sul sites,respectively.Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate.Trace elements,especially Cu,Pb,Zn,Cd,and Ni also made important contributions which are directly associated with anthropogenic contributions.Our results show significantly higher levels in winter than in summer.Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources,especially road traffic,combustion processes and industrial activities,which are grouped in 7 major contributing sources.A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations.This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions,combined with awareness-raising actions for citizens concerning the impact of indoor sources.  相似文献