Brown algae overproduce cell wall polysaccharides as a protection mechanism against the heavy metal toxicity   总被引：4，自引：0，他引：4  

Leonardo R. Andrade  Raquel N. Leal  Miguel Noseda  Mariana S. Pereira  Marcos Farina 《Marine pollution bulletin》2010,60(9):1482-1488

Brown algae are often used as heavy metal biomonitors and biosorbents because they can accumulate high concentrations of metals. Cation-exchange performed by cell wall polysaccharides is pointed out as the main chemical mechanism for the metal sequestration. Here, we biochemically investigated if the brown alga Padina gymnospora living in a heavy metal contaminated area would modify their polysaccharidic content. We exposed non-living biomass to Cd and Pb and studied the metals adsorption and localization. We found that raw dried polysaccharides, sulfate groups, uronic acids, fucose, mannose, and galactose were significantly higher in contaminated algae compared with the control ones. Metal concentrations adsorbed by non-living biomass were rising comparatively to the tested concentrations. Electron microscopy showed numerous granules in the cell walls and X-ray microanalysis revealed Cd as the main element. We concluded that P. gymnospora overproduces cell wall polysaccharides when exposed to high metal concentrations as a defense mechanism.  相似文献   

Atmospheric inorganic aerosol of a non-industrial city in the centre of an industrial region of the North of Spain,and its possible influence on the climate on a regional scale     

Irene Rodríguez  Salvador Galí  Celia Marcos 《Environmental Geology》2009,56(8):1551-1561

Mineral particles could have influenced on the climate of Oviedo, a non-industrial city situated in the centre of an industrial zone of the North of Spain, increasing the temperature and the precipitations, in spite of the fact that “greenhouse gases” concentrations have diminished in this city in recent years. The directive (1999/30/EC) of the European Commission began to be applied in Oviedo in the year 2003. In agreement with this norm, our first aim was the identification of the inorganic particulate matter of the PM10 and PM2.5 fractions sampled in this city. X-ray diffraction and scanning electron microscopy coupled with X-ray dispersive energy spectrometry were used. The percentages of the different mineral phases of the PM were obtained by a Rietveld refinement of powder X-ray diffraction data. The compositions of the PM10 and PM2.5 fractions of this city are similar. Sulphates are the most abundant particles in the both fractions. Most sulphates, nitrates and sal-ammoniac would have formed by reaction between solid, liquid and/or gas particles and they could be associated with the power stations near to the city and traffic. Wüstite and haematites come from the iron and steel industries of Gijón and Avilés. The main natural sources of halite and carbonates and silicates are sea spray and soil resuspension by the wind, respectively.  相似文献   

Characterization of shape and terminal velocity of tephra particles erupted during the 2002 eruption of Etna volcano,Italy     

M. Coltelli  L. Miraglia  S. Scollo 《Bulletin of Volcanology》2008,70(9):1103-1112

In this paper, we present a complete morphological characterization of the ash particles erupted on 18 December 2002 from Etna volcano, Italy. The work is based on the acquisition and processing of bidimensional digital images carried out by scanning electron microscopy (SEM) to obtain shape parameters by image analysis. We measure aspect ratio (AR), form factor (FF), compactness (CC), and rectangularity (RT) of 2065 ash particles with size between 0.026 and 1.122 mm. We evaluate the variation of these parameters as a function of the grain-size. Ash particles with a diameter of <0.125 mm vary from mostly equant to very equant, ash particles between 0.125 and 0.250 mm have an intermediate shape, and particles with diameters >0.250 mm are subelongate. We find that, on average, particles with a diameter of <0.250 mm are subrounded, particles between 0.250 and 0.50 mm are subangular, and particles >0.50 mm are angular. Using this morphological analysis and an empirical relation between the drag coefficient (C _D) and Reynolds number (R _e) of Wilson and Huang (Earth Planet Sci Lett 44:311–324, 1979), we calculate the terminal settling velocities (V _WH). The comparisons between these velocities and those calculated with the formula of Kunii and Levenspiel (Fluidization engineering. Wiley, New York, pp 97, 1969) (V _KL), which considers ash particles as spheres, show that V _KL are in average 1.28 greater than V _WH. Hence, we quantify the systematic error on the spatial distribution of the mass computed around the volcano carried out by tephra dispersal models when the particles are assumed to be spherical.  相似文献   

Structural modulations and phase transitions in β-eucryptite: an in-situ TEM study     

H. Xu  P. J. Heaney  H. Böhm 《Physics and Chemistry of Minerals》1999,26(8):633-643

Beta-eucryptite as grown by the flux method has been investigated by in-situ cold- and hot-stage transmission electron microscopy (TEM). Using electron diffraction and dark-field TEM imaging, we found no evidence for the merohedral twinning that accompanies structural collapse at the β-to-α-quartz transition, suggesting a true hexagonal symmetry for the aluminosilicate framework of β-eucryptite. Selected-area electron diffraction (SAED) patterns exhibited a variety of incommensurate structures along the three a axes with an average modulation period of about 6.5 a. These modulated structures arise from superperiodic stacking parallel to (100) of two structural units with different Li configurations. In-situ heating experiments show that the modulated structures undergo a reversible transition to the disordered modification at elevated temperatures. This transition arises from positional order-disorder of Li ions along the main structural channels. In addition, it appears that at constant low temperature, electron beam irradiation alone can induce a sequence of transitions similar to those that are thermally induced from the ordered modification to modulated states. Received: 12 November 1998 / Revised and accepted: 31 December 1998  相似文献   

文昌鱼卵母细胞发育成熟过程中高尔基复合体数量的变化   总被引：1，自引：0，他引：1  

方永强  林秋明  齐襄 《台湾海峡》1992,(1)

本工作采用细胞学和电子显微镜技术,较详细观察了文昌鱼卵细胞在发育成熟过程中高尔基复合体数量的变化。研究结果表明,高尔基体的数量变化可作为卵母细胞发育成熟的标志,可为确定文昌鱼卵巢成熟度提供科学依据。  相似文献   

文蛤外套腔中一种寄生桡足类的扫描电镜观察   总被引：2，自引：0，他引：2  

郑国兴  于业绍 《海洋学研究》1995,13(2):21-25

本文应用扫描电镜对寄生于文蛤外套腔中的一种桡足类Ｏｓｔｒｉｎｃｏｌａｋｏｅ的外部形态进行了观察。该桡足类是作者于１９８８和１９８９年秋季，在江苏南部沿海文蛤大批死亡原因调查时，在文蛤外套腔中发现的。寄生于贝类的桡足类在我国属首次报道。  相似文献   

大理苍山世界地质公园第四纪冰碛物特征及年代测定     

顾佳妮  陈安东  赵志中  姚海涛  李志明  张青 《地球学报》2016,37(6):769-778

云南大理苍山世界地质公园具有较高的美学价值与地学科研价值,在地学研究领域中苍山又被称为点苍山。本次研究的主要区域是点苍山玉局峰北坡和点苍山西北部的罗坪山大小海子地区,本文对点苍山玉局峰北坡冰碛物和罗坪山第四纪沉积物进行了光释光年代测定,讨论了光释光测年方法在点苍山地区第四纪冰碛物测年中的适用性,测得玉局峰北坡搬运距离较远的三条冰碛垄的年龄为(31.68±3.22)~(28.01±1.95)ka BP,属于末次冰期。对罗坪山地区第四纪沉积物进行石英砂扫描电镜分析,观察到大小海子附近第四纪沉积物石英砂表面具有一定的冰川成因特征,推断罗坪山大小海子地区曾发育过第四纪冰川作用,通过光释光测年得到大小海子附近冰川沉积物年代为(136.36±10.16)ka BP,相当于倒数第二次冰期。结合前人研究,推断点苍山地区也具有发育倒数第二次冰期的可能性。  相似文献   

宁镇地区下志留统高家边组富有机质页岩孔隙结构          下载免费PDF全文

李晋宁  姚素平  孙超  丁海 《高校地质学报》2016,22(1):159

通过氩离子抛光-场发射扫描电镜、小角X射线散射及低温氮气吸附实验,对宁镇地区下志留统仑山5井等高家边组底部富有机质泥页岩孔隙结构进行分析,为下扬子区下志留统富有机质泥页岩的储层评价提供依据。研究表明:高家边组富有机质泥页岩含有大量的纳米级孔隙,包括有机质孔、矿物粒间孔、矿物粒内孔、微裂缝等,孔径分布复杂;优势孔径分布为介孔段,孔隙直径主要为2~50 nm。影响孔径分布的主要因素是矿物组成,脆性矿物和黏土矿物对微孔和介孔都有一定的影响,而有机质含量对泥页岩总体孔隙特征的影响并不明显。  相似文献   

Crystallization behavior of Na2SO4–MgSO4 salt mixtures in sandstone and comparison to single salt behavior     

《Applied Geochemistry》2016

We report on the crystallization behavior and the salt weathering potential of Na₂SO₄, MgSO₄ and an equimolar mixture of these salts in natural rock and porous stone. Geochemical modeling of the phase diagram of the ternary Na₂SO₄–MgSO₄–H₂O system was used to determine the equilibrium pathways during wetting (or deliquescence) of incongruently soluble minerals and evaporation of mixed electrolyte solutions. Model calculations include stable and metastable solubilities of the various hydrated states of the single salts and the double salts Na₂Mg(SO₄)₂·4H₂O (bloedite), Na₂Mg(SO₄)₂·5H₂O (konyaite), Na₁₂Mg₇(SO₄)₁₃·15H₂O (loeweite) and Na₆Mg(SO₄)₄ (vanthoffite). In situ Raman spectroscopy was used to study the phase transformations during wetting of pure MgSO₄·H₂O (kieserite) and of the incongruently soluble salts bloedite and konyaite. Dissolution of kieserite leads to high supersaturation resulting in crystallization of higher hydrated phases, i.e. MgSO₄·7H₂O (epsomite) and MgSO₄·6H₂O (hexahydrite). This confirms the high damage potential of magnesium sulfate in salt damage of building materials. The dissolution of the incongruently soluble double salts leads to supersaturation with respect to Na₂SO₄·10H₂O (mirabilite). However, the supersaturation was insufficient for mirabilite nucleation. The damage potential of the two single salts and an equimolar salt mixture was tested in wetting–drying experiments with porous sandstone. While the high damage potential of the single salts is confirmed, it appears that the supersaturation achieved during wetting of the double salts at room temperature is not sufficient to generate high crystallization pressures. In contrast, very high damage potentials of the double salts were found in experiments at low temperature under high salt load.1  相似文献   

Organic matter of the liquid phase of peat and its hydrolyzates from the deposits of the Middle Amur basin     

V. V. Chakov  N. V. Berdnikov  N. S. Konovalova 《Russian Journal of Pacific Geology》2008,2(6):553-556

The liquid phase of peat from the deposits of the Middle Amur basin was investigated by scanning electron microscopy and energy dispersive analysis in order to estimate the possibility of obtaining new sorbents on its basis. It was shown that organic compounds with fractal forms and properties can be obtained on the basis of peat hydrolyzate. The concentration of carbon in them corresponds to the composition of the humic complexes extracted from peat deposits. The resulting high-molecular-weight compounds actively sorb small organic particles. The samples investigated can be used to develop a fundamentally new class of efficient petroleum sorbents.  相似文献