Correlations between metal uptake in the soft tissue of Perna perna and gill filament pathology after exposure to mercury     

Gregory MA  Marshall DJ  George RC  Anandraj A  McClurg TP 《Marine pollution bulletin》2002,45(1-12):114-125

The accumulation of metal in soft tissues, filtration rate and gill filament morphology are correlated in the southern African rock mussel, Perna perna, during exposure to mercury (24 days) and recovery (24 days). The amount of Hg in soft tissues increased from 0.13 to 87.5 μg/g dry weight after 24 days exposure, and declined to 13 μg/g during recovery. Mean filtration rate fell from 3979 to 1818 ml/h/g dry weight by day 2, but recovered slightly through days 4 and 8 (3037 ml/h/g), with a higher average rate (5030 ml/h/g) being maintained over the 24–48 days recovery period. The initial decline in filtration coincided with epithelial cell deterioration presented as interstitial oedema, neural and epithelial cell degeneration and reduced ciliation. Between days 8 and 24, cilia regenerated and there was a general improvement in cell morphology. Gill filament morphology returned to near normal during the metal-free recovery period. The usefulness of P. perna as an indicator of pollution is discussed.  相似文献   

氟碳钙铈矿结构中晶体缺陷的高分辨电镜研究   总被引：1，自引：1，他引：1  

孟大维  吴秀玲 《矿物学报》1995,15(4):378-382

用高分辨电子显微术（ＨＲＥＭ）研究了氟碳钙铈矿（ＢＳ）晶体结构中的无序堆垛和体衍交生现象，结果表明该矿物的衍生多晶体是由钙－铈氟碳酸盐矿物中不同组分的氟碳铈矿（Ｂ）和直氟碳钙铈矿（Ｓ）结构单元层沿ｃ方向无序堆垛而成。高分辨结构象揭示出氟碳钙铈矿衍生多晶体的微结构特征。讨论了氟碳钙铈矿结构中的堆垛层错等晶体缺陷现象。  相似文献   

Rock-weathering by the lichen Lecidea auriculata in an arctic alpine environment   总被引：1，自引：0，他引：1  

Danny McCarroll  Heather Viles 《地球表面变化过程与地形》1995,20(3):199-206

Scanning electron microscopy reveals that Lecidea auriculata penetrates rock surfaces, detaching, incorporating and expelling flakes of rock. Measurements on an age sequence of moraine ridges illustrate changes in the extent and intensity of weathering over time. A minimum rate of surface lowering (0·0012 mm a^?1) is 25 to 50 times faster than weathering due to other processes in the same area. The spatial pattern of weathering is influenced by the narrow ecological range of the species. Surface rocks on dry, exposed sites are probably weathering much more rapidly than those in adjacent damp hollows and beneath snowpatches.  相似文献   

Direct scanning tunneling microscope (STM) observation of Cr(III) complexes on hematite (001) surfaces     

Carrick M. Eggleston 《Aquatic Sciences - Research Across Boundaries》1993,55(4):240-249

Scanning tunneling microscopy (STM) is used to observe, at the atomic scale, Cr(III) adsorbed to hematite (001) surfaces from aqueous solution. The Cr(III) adsorbates are relatively immobile, but estimated activation energies for surface self-diffusion are lower than those for water or hydroxyl substitution in aqueous Cr(III). Possible causes are effects of STM imaging (artifacts), high ligand-substitution rates for adsorbed species, or participation of substrate Fe (III) ligand exchange. STM imaging of suitable aqueous surface complexes is shown to be feasible, and constitutes a new way to study the relationships between microscopic and macroscopic chemical behavior of adsorbed species in aqueous systems.  相似文献   

Bimodal Density Distribution of Cryptodome Dacite from the 1980 Eruption of Mount St. Helens,Washington     

Richard P. Hoblitt  Russell S. Harmon 《Bulletin of Volcanology》1993,55(6):421-437

The explosion of a cryptodome at Mount St. Helens in 1980 produced two juvenile rock types that are derived from the same source magma. Their differences-color, texture and density-are due only to vesicularity differences. The vesicular gray dacite comprises bout 72% of the juvenile material; the black dacite comprises the other 28%. The density of juvenile dacite is bimodally distributed, with peaks at 1.6 g cm^-3 (gray dacite) and 2.3 g cm^-3 (black dacite). Water contents, deuterium abundances, and the relationship of petrographic structures to vapor-phase crystals indicate both rock types underwent pre-explosion subsurface vesiculation and degassing. The gray dacite underwent a second vesiculation event, probably during the 18 May explosion. In the subsurface, gases probably escaped through interconnected vesicles into the permeable volcanic edifice. We suggest that nonuniform degassing of an initially homogeneous magma produced volatile gradients in the cryptodome and that these gradients were responsible for the density bimodality. That is, water contents less than about 0.2–0.4 wt% produced vesicle growth rates that were slow in comparison to the pyroclast cooling rates; greater water contents produced vesicle growth rates that were fast in comparison to cooling rates. In this scheme, the dacite densities are bimodally distributed simply because, following decompression on 18 May 1980, one clast population vesiculated while the other did not. For clasts that did vesiculate, vesicle growth continued until it was arrested by fragmentation.  相似文献   

The geochemistry of exinites—1. Evaluation of spectral fluorescence of a series of modern resins and fossil resinites     

Joseph T. Senftle  Stephen R. Larter   《Organic Geochemistry》1988,13(4-6)

A series of six fossil resins and four modern resins have been analysed using microscope-based spectral fluorescence methods, in addition to a preliminary study of the chemical composition of these samples using infrared spectroscopy and pyrolysis-gas chromatography. This study illustrates problems encountered during the measurement of spectral fluorescence of resins and resinite kerogens using conventional microscopy methods. Most notable, alteration of fluorescence significantly influences spectral measurements. Further, fossilized resins within rocks are complex mixtures of resinite and bitumen. Pre-extraction of resinites prior to petrographic analysis resulted in somewhat more uniform spectral fluorescence results.Spectral fluorescence of recent resins used in this study could be used to distinguish angiosperm from gymnosperm derived resinite kerogens. Distinction of plant class source of resinite kerogens, however, is more difficult using this method and is considered genarally unreliable.  相似文献   

煤核的高分辨电镜观察     

阎桂环  王岩国 《矿物学报》1989,9(3):262-268

利用高分辨电子显微镜(HREM)和光学衍射的方法,对分别加热400℃和800℃处理的煤样进行了研究,并与未加热的煤样进行了对比。高分辨像清楚地显示了煤核的形态。常温下,煤核的尺度为纳米量级;加热400℃处理后,长大到十纳米量级;对800℃的情况,有次生结构出现,使煤核减小到纳米量级,同时高分辨像和光学衍射均表明煤核中有孪晶存在。  相似文献   

Importance of environment on the order of mineral weathering in olivine basalts,Hawaii     

Thad A. Wasklewicz 《地球表面变化过程与地形》1994,19(8):715-734

Examination of weathering rinds from lava flows on Hawaii with backscatter electron microscopy and electron micro-probe analysis reveals that olivine weathers more slowly than adjacent clinopyroxene and plagioclase in environments with a paucity of organic acids. Yet when weathering rinds are in contact with abundant organic acids secreted by lichens, olivine weathers before clinopyroxene and plagioclase weathers last. The exception to Goldich's widely accepted mineral stability series in organic-poor environments runs counter to a thermodynamics explanation for the order of mineral weathering and illustrates the importance of the biogeochemical environment.  相似文献   

Can magnetic-force microscopy determine micromagnetic structures?     

P. Grütter  R. Allenspach 《Geophysical Journal International》1994,116(2):502-505

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莱河矿超结构的高分辨电镜研究     

邹本三  郭可信 《矿物学报》1987,(1)

用高分辨电子显微术和光学衍射技术研究了莱河矿的三种超结构类型——3C_1,2C,3C_2。超结构的存在是由于Fe~(2+)空位的不同有序分布产生的。通过观察象与模拟象的比较,建立了相应的结构模型。  相似文献