Seasonal variation in abundance and species composition of a planktonic diatom assemblage including viable cells on the bottom in matsushima bay,northeastern japan     

ICHINOMIYA Mutsuo  TANIGUCHI Akira 《中国海洋大学学报(英文版)》2003,2(2):160-166

Seasonal variation in abundance and species composition of a planktonic diatom assemblage distributed in the water column and also settled on the bottom was investigated for the shallow coastal water in Matsushima Bay on the Pacific coast of northeastern Japan during the period from October 1999 to September 2000. A spring bloom of diatoms began in April when nutrient concentrations started to increase, indicating the importance of nutrients. Viable cells of Skeletonema costatum and Thalassiosira spp., which were the dominant species in the water column throughout the year, were also always abundant in the bottom sediment. Both populations in the water column and on the bottom fluctuated essentially in parallel. For the planktonic diatoms in shallow coastal waters to maintain their vegetative populations in the water column, it would be advantageous for them to have a seeding population of viable cells on the bottom that are easily resuspended into the upper photic layer.  相似文献   

Study of the Interaction between Biological Cells of Different Shapes and Sizes and Electromagnetic Fields Produced by Natural Phenomena     

Diaz-Sandoval  Rosa  Mendoza  Blanca 《Natural Hazards》2004,31(1):143-156

We carry out a study of the interaction between electromagnetic fields produced innature and cells with no structure but with different shapes and sizes, considered asapproximations of those observed in the human body. Magnetic fields produced byvarious atmospheric and geomagnetic phenomena are compared with the fieldsgenerated by the cells themselves. Working with frequencies up to 10⁵ Hz, we found that in most cases lightning is the natural phenomena capable of producingfield intensities comparable to those generated by the cells. As a first approximationwe assume that a cell might be affected only if a field of intensity comparable to thecell's field is present. Oscillating fields of less intensity and their harmonics can involveresonant interactions with the cells, however this situation is not considered here. Under the approximation of our study we found that the size and the shape are parameters of paramount importance: lightning represents a natural hazard only for the largest cells, while the quadrangular cells are not affected by any of the natural phenomena considered here.  相似文献   

非水溶剂中电解质溶液活度系数的测定:NaCl在1,2-丙二醇中活度系数的测定   总被引：10，自引：3，他引：10       下载免费PDF全文

王卫东  向翠丽  胡珍珠  陆江林 《盐湖研究》2004,12(1):43-45

应用钠离子选择性电极和Ag-AgCl电极组成可逆电池,通过测定电池的电动势,应用Debye H櫣ckel极限公式,计算了不同温度下NaCl在1,2-丙二醇非水溶剂中的活度系数,并根据电解质溶液的溶剂化理论对NaCl的活度系数的某些变化规律进行了讨论。  相似文献   

反浮选-冷结晶法生产氯化钾浮选法除钙研究   总被引：5，自引：1，他引：5       下载免费PDF全文

牛桂然  唐宏学 《盐湖研究》2006,14(1):14-16

研究了青海察尔汗盐湖水采光卤石矿生产氯化钾工艺中浮选除钙的方法。实验结果表明,分级浮选法除钙率平均达88.16%,接近原矿的理论可除钙离子量91.58%。  相似文献   

Hydrogen from coal: Production and utilisation technologies   总被引：2，自引：0，他引：2  

E. Shoko  B. McLellan  A.L. Dicks  J.C. Diniz da Costa   《International Journal of Coal Geology》2006,65(3-4):213-222

Although coal may be viewed as a dirty fuel due to its high greenhouse emissions when combusted, a strong case can be made for coal to be a major world source of clean H₂ energy. Apart from the fact that resources of coal will outlast oil and natural gas by centuries, there is a shift towards developing environmentally benign coal technologies, which can lead to high energy conversion efficiencies and low air pollution emissions as compared to conventional coal fired power generation plant. There are currently several world research and industrial development projects in the areas of Integrated Gasification Combined Cycles (IGCC) and Integrated Gasification Fuel Cell (IGFC) systems. In such systems, there is a need to integrate complex unit operations including gasifiers, gas separation and cleaning units, water gas shift reactors, turbines, heat exchangers, steam generators and fuel cells. IGFC systems tested in the USA, Europe and Japan employing gasifiers (Texaco, Lurgi and Eagle) and fuel cells have resulted in energy conversions at efficiency of 47.5% (HHV) which is much higher than the 30–35% efficiency of conventional coal fired power generation. Solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC) are the front runners in energy production from coal gases. These fuel cells can operate at high temperatures and are robust to gas poisoning impurities. IGCC and IGFC technologies are expensive and currently economically uncompetitive as compared to established and mature power generation technology. However, further efficiency and technology improvements coupled with world pressures on limitation of greenhouse gases and other gaseous pollutants could make IGCC/IGFC technically and economically viable for hydrogen production and utilisation in clean and environmentally benign energy systems.  相似文献   

氯化钠存在下氯化亚锡-十六烷基三甲基氯化铵体系浮选分离复杂金属基体中锇   总被引：1，自引：0，他引：1  

高云涛 杨宏施润菊  项朋志 《岩矿测试》2006,25(3):246-248

研究了氯化钠存在下氯化亚锡-十六烷基三甲基氯化铵体系对Os（Ⅳ）-三氯锡酸络阴离子的浮选行为。实验表明，在盐酸介质中，体系可以浮选分离Os（Ⅳ），其浮选率为95．2％。98.0％。方法加标回收率为94．0％-98．5％，精密度为2．1％-7．7％（RSD，n=5）。方法可用于从大量基体金属中分离Os（Ⅳ），对实际样品分离的分析结果与其他方法推荐值相符。  相似文献   

Isotopic Composition of Non-Methane Hydrocarbons in Emissions from Biomass Burning     

K. v. Czapiewski  E. Czuba  L. Huang  D. Ernst  A.L. Norman  R. Koppmann  J. Rudolph 《Journal of Atmospheric Chemistry》2002,43(1):45-60

The stable carbon isotope ratios of nonmethane hydrocarbons (NMHC) and methyl chloride emitted from biomass burning were determined by analyzing seven whole air samples collected during different phases of the burning process as part of a laboratory study of wood burning. The average of the stable carbon isotope ratios of emitted alkanes, alkenes and aromatic compounds is identical to that of the burnt fuel; more than 50% of the values are within a range of ±1.5 of thecomposition of the burnt fuel wood. Thus for the majority of NMHC emitted from biomass burning stable carbon isotope ratio of the burnt fuel a good first order approximation for the isotopic composition of the emissions. Of the more than twenty compounds we studied, only methyl chloride and ethyne differed in stable carbon isotope ratios by more than a few per mil from the composition of the fuel. Ethyne is enriched in ¹³C by approximately 20–30, and most of the variability can beexplained by a dependence on flame temperature. The ¹³C values decreaseby 0.019 /K (±0.0053/K) with increasing temperature. Methyl chloride is highly depleted in ¹³C, on average by25. However the results cover a wide range of nearly 30. Specifically, in two measurements with wood from Eucalyptus (Eucalyptus delegatensis) as fuel we observed the emission of extremely light methyl chloride (–68.5and–65.5). This coincides with higher than average emission ratiosfor methyl chloride (15.5 × 10^–5 and 18 ×10^–5 mol CH₃Cl/mol CO₂). These high emission ratios are consistent with the highchlorine content of the burnt fuel, although, due to the limited number of measurements, it would be premature to generalize these findings. The limited number of observations also prevents any conclusion on a systematic dependence between chlorine content of the fuel, emission ratios and stable carbon isotope ratio of methyl chloride emissions. However, our results show that a detailed understanding of the emissions of methyl chloride from chloride rich fuels is important for understanding its global budget. It is also evident that the usefulness of stable carbon isotope ratios to constrain the global budget of methyl chloride will be complicated by the very large variability of the stable carbon isotope ratio of biomass burning emissions. Nevertheless, ultimately the large fractionation may provide additional constraints for the contribution of biomass burning emissions to the atmospheric budget of methyl chloride.  相似文献   

Sur l'origine par altération du substratum schisteux de la minéralisation chlorurée des eaux d'une nappe côtière sous climat semi-aride (Chtouka-Massa,Maroc)     

Samira Krimissa  Jean-Luc Michelot  Lhoussaine Bouchaou  Jacques Mudry  Youssef Hsissou 《Comptes Rendus Geoscience》2004,336(15):1363-1369

The origin of chloride ions in groundwater from the Chtouka-Massa plain (Morocco) was studied by using chemical and isotopic analyses of water, and petrographic and chemical analyses of rocks. It appears that the schist formation, which forms the basement of the studied aquifer, is the main source of the high Cl^? concentrations in groundwater. In these schists, chloride is, for a part, probably contained in biotites, and is released into groundwater through the weathering of these minerals. However, the exceptionally high chloride contents of these schists are difficult to explain if one does not assume that they also contain evaporitic-type minerals. To cite this article: S. Krimissa et al., C. R. Geoscience 336 (2004).  相似文献   

Regional Sources of Methyl Chloride, Chloroform and Dichloromethane Identified from AGAGE Observations at Cape Grim, Tasmania, 1998–2000     

M. L. Cox  G. A. Sturrock  P. J. Fraser  S. T. Siems  P. B. Krummel  S. O'Doherty 《Journal of Atmospheric Chemistry》2003,45(1):79-99

There are large uncertainties in identifying and quantifying the natural and anthropogenic sources of chloromethanes – methyl chloride (CH₃Cl), chloroform (CHCl₃) and dichloromethane (CH₂Cl₂), which are responsible for about 15% of the total chlorine in the stratosphere. We report two years of in situ observations of these species from the AGAGE (Advanced Global Atmospheric Gas Experiment) program at Cape Grim, Tasmania (41° S, 145° E). The average background levels of CH₃Cl, CHCl₃ and CH₂Cl₂ during 1998–2000 were 551± 8, 6.3± 0.2 and 8.9± 0.2 ppt (dry air mole fractions expressed in parts per 10¹²) respectively, with a two-year average amplitude of the seasonal cycles in background air of 25, 1.1 and 1.5 ppt respectively. The CH₃Cl and CHCl₃ records at Cape Grim show clear episodes of elevated mixing ratios up to 1300 ppt and 55 ppt respectively, which are highly correlated, suggesting common source(s). Trajectory analyses show that the sources of CH₃Cl and CHCl₃ that are responsible for these elevated observations are located in coastal-terrestrial and/or coastal-seawater regions in Tasmania and the south-eastern Australian mainland. Elevated levels of CH₂Cl₂ (up to 70 ppt above background) are associated mainly with emissions from the Melbourne/Port Phillip region, a large urban/industrial complex (population 3.5 million) 300 km north of Cape Grim.Now at the Centre for Atmospheric ChemistryNow at School of Environmental Sciences  相似文献   

Enviromental genotoxicity evaluation: Bayesian approach for a mixture statistical model     

A. M. de S. Bueno  C. A. de B. Pereira  M. N. Rabello-Gay  J. M. Stern 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(4):267-278

 The data analyzed in this paper are part of the results described in Bueno et al. (2000). Three cytogenetics endpoints were analyzed in three populations of a species of wild rodent – Akodon montensis – living in an industrial, an agricultural, and a preservation area at the Itajaí Valley, State of Santa Catarina, Brazil. The polychromatic/normochromatic ratio, the mitotic index, and the frequency of micronucleated polychromatic erythrocites were used in an attempt to establish a genotoxic profile of each area. It was assumed that the three populations were in the same conditions with respect to the influence of confounding factors such as animal age, health, nutrition status, presence of pathogens, and intra- and inter-populational genetic variability. Therefore, any differences found in the endpoints analyzed could be attributed to the external agents present in each area. The statistical models used in this paper are mixtures of negative-binomials and Poisson variables. The Poisson variables are used as approximations of binomials for rare events. The mixing distributions are beta densities. The statistical analyzes are under the bayesian perspective, as opposed to the frequentist ones often considered in the literature, as for instance in Bueno et al. (2000).  相似文献