地质微生物响应地质环境变化的若干问题--兼论环境代用指标的应用

微生物能够通过改变细胞膜脂类成分而灵敏地响应地质环境条件的变化,使得人们建立了一系列微生物的古环境代用指标。应用比较广泛的古温度定量化指标包括藻类的长链烯酮U_(37)~k、古菌甘油二烷基甘油四醚的TEX_(86),以及细菌甘油二烷基甘油四醚的MBT/CBT等。然而,由于缺乏生理学和生态学分析,人们在应用微生物的环境代用指标时不断发现适用性问题。论文重点从微生物对环境响应的化学过程、生理范围和生态效应这三方面分析了一些环境代用指标在应用时需要考虑的多指标相互验证、线性范围和灵敏度,以及地区性差异等问题。微生物通过脂类响应环境变化有多种化学方式和途径可以实现,使得许多代用指标可以相互验证。微生物对地质环境的生理响应是有线性范围的,这决定了微生物脂类的环境代用指标的灵敏度大小。而微生物对环境因子的生态响应则决定了代用指标的应用存在地区性差异。某种环境的微生物活动往往受到一些限制性因子控制,相应地一些微生物脂类的环境代用指标也主要响应这些限制性环境因子的变化。微生物的古环境代用指标的应用不仅需要了解微生物通过脂类响应环境变化的化学机理,更要了解相应微生物的生理学和生态学原理。     

The fat of the land: a geography of oil and fat consumption

Lipids – or oils and fats – have attracted much attention in nutrition and medical research because of their adverse effects upon health, but the geography of lipids has received very little notice. International differences in consumption can be calculated from the Food and Agriculture Organization's Food Balance Sheets. Consumption was very low in the early nineteenth century, but increased as incomes rose and more animal foods were consumed, whilst technical advances allowed the use of a wide range of vegetable oils per capita. Consumption of total lipids is greatest in North America, Europe, Australasia and temperate South America, lowest in Asia, reflecting differences in income, although other factors are important. The sources of animal and plant lipids are discussed and their changing relative importance over time is traced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organic geochemical evidence for environmental changes since 34,000 yrs BP from Lago di Mezzano, central Italy

The composition of organic matter in a 34,000 yr sediment profile from Lago di Mezzano, central Italy, was investigated by bulk organic geochemical methods and analyses of lipid distributions. High relative amounts of long-chain fatty acids, n-alkanols and n-alkanes from the cuticular waxes of terrestrial plants in the Late Pleistocene sediments indicate a high relative proportion of allochthonous organic matter. In the Holocene sediments higher relative amounts of algal and bacterial lipids are detected which indicate a higher relative contribution of autochthonous organic matter. These results are corroborated by Hydrogen Index (HI) and Oxygen Index (OI) values from Rock-Eval pyrolysis which show a good general correlation with the TOC content indicating significant variations of the organic matter composition. Variations of HI and OI observed for different lithozones of the sediment profile can be related to environmental and climatic changes throughout the lake history. Both bulk organic geochemical and molecular data point to a good overall preservation of the organic matter.     

泡沫镍为集流体的膜电容去离子脱盐性能研究

文章为了解决淡水资源短缺这一严峻的问题,考虑将能耗小、无化学再生等优点的膜电容去离子技术作为基础,对其进行改进与优化,即将低电阻、高比表面积和高孔隙率的泡沫镍替代传统集流体。并利用改进后的装置进行实验,分别探讨电极材料、电压和盐水流速等因素对脱盐效率的影响。将未加电极材料和加3种不同的活性炭作为电极材料的装置进行脱盐实验,根据结果得出,在脱盐过程中起主要作用的仍然是电吸附过程,通过进一步对电极材料进行表征,讨论得出脱盐效率与比表面积和孔径分布均有关系。随后在最优电极材料的条件下,讨论得出最优的操作条件,即在施加电压为1.6 V、盐水流速为10 mL/min下可以达到最佳的脱盐效率,吸附量为8.9 mg/g。且通过长时间的吸脱附实验得出电极材料AC1具有良好的再生能力。     

光合膜膜脂在八种海洋硅藻中的分布研究

利用超高效液相色谱-四级杆-飞行时间串联质谱(UPLC-Q-TOF-MS)对8种海洋硅藻的四种主要光合膜膜脂的分子结构和组成进行了定性定量分析。结果表明,海洋硅藻中MGDG含量最高,占四种光合膜膜脂的40%~70%左右,SQDG其次占10%~40%,而PG在4%~20%之间,DGDG占5%~20%;其中,各脂类分子的含量在0.14~99.79 nmol/mg干藻之间,而C_16:3/C_16:3-MGDG,C_20:5/C_16:3-MGDG,C_20:5/C_16:2-DGDG,C_20:5/C_16:1-DGDG,C_16:1/C_16:1-DGDG,C_14:0/C_14:0-SQDG,C_14:0/C_16:0-SQDG,C_14:0/16:1-SQDG,C_14:0/C_16:3-SQDG和C_18:1/C_18:1-PG等脂类分子在8种海洋硅藻的每一类膜脂中均有分布;与高等植物膜脂的脂肪酰基分布不同的是,海洋硅藻的MGDG与DGDG的sn-2位上的脂肪酸全部为C₁₆酸,可推断是通过类似高等植物典型的原核途径合成,而C₁₆酸和C₁₈酸在SQDG和PG的sn-2位上均有分布,可推断SQDG和PG存在原核和真核两种合成途径。     

海洋环境中的厌氧氨氧化细菌与厌氧氨氧化作用

厌氧氨氧化是细菌在厌氧条件下将氨氮氧化成氮气的过程,主要应用在污水处理反应器中,最近几年发现在海洋环境中也广泛存在,并在海洋氮循环过程中发挥了重要作用,代表了海洋中一个巨大的氮汇,对碳循环和全球气候变化也有重要影响。梯烷膜脂结构独特,是厌氧氨氧化细菌的化学生物标志物,具有化学分类与古海洋学应用潜力。厌氧氨氧化作用及厌氧氨氧化细菌已成为海洋生物地球化学、微生物学、有机地球化学等研究领域的热点。     

Red spruce canopy response to acid fog exposure

The health of red spruce is adversely affected by exposure to acid fog. Epicuticular wax structure over epistomatal chambers, mesophyll membrane calcium and changes in redox state of glutathione are affected in both chamber and field studies and are correlated with leaf exposure to acid fog, but not with soil or total leaf calcium concentrations. Experiments tracking fog deposition under conditions of illumination or darkness, with or without a metabolic inhibitor, support the mechanism of diffusiophoresis linked with photosynthetic gas exchange. Based on deposition pattern and leaf morphology, a stomatal pathway for water and hydrogen ion penetration to leaf interior is proposed. Ecophysiological parameters are discussed in relation to differential sensitivities of red spruce and white pine to ozone and acid fog.     

Surface-penetrating flexible membrane wave barriers of finite draft

The performance of surface-penetrating flexible membrane wave barriers of finite draft is studied. The interactions of a single membrane and dual membrane systems are examined with various system parameters. The analytical solutions are derived using eigenfunction expansions assuming linear wave theory and small membrane response. Wave transmission is determined for various combinations of membrane draft, protrusion above the water surface, membrane tension and membrane spacing. The numerical solutions are compared with data obtained from experiments conducted. Comparisons of transmission coefficient and energy loss show good agreement with suitably chosen parameters of viscous losses.     

Phytopigments and fatty acids as molecular markers for the quality of near-bottom particulate organic matter in the North Sea

In February, May and August 1994, four stations in the North Sea (viz. at the Broad Fourteens, Frisian Front, German Bight and Skagerrak) were visited to sample near-bottom particulate organic matter. Samples, taken by means of a pump, a sediment trap and a sediment recorder, were analysed on organic carbon, total nitrogen, phytopigments and fatty acids. These molecular markers were used to describe the nature and quality of the organic particles in the near-bottom water. Principal component analysis showed chlorophyll a, phaeopigments and fatty acids to be useful markers for the quality of organic matter and yield complementary information.The quality of the near-bottom particles appeared to be related to the local hydrography and depositional circumstances. The Broad Fourteens station, a non-depositional sandy site along the Dutch coast, showed organic particles to be relatively fresh, little influenced by resuspended sedimentary material. Near-bottom organic particles on this site contained relatively high shares of chlorophyll a and polyunsaturated fatty acids, characteristic of algal matter. On the other hand the particulate organic material on the two depositional locations, the Frisian Front and the German Bight stations, was influenced by resuspension of sedimentary organic particles poor in pigments and fatty acids. Amounts of carbon trapped in the near-bottom environment at the Skagerrak station were lower than expected from the literature.     

久效磷对海洋微藻细胞的活性氧伤害

于1994年8月－1995年12月运用生态毒理学和生物化学实验方法对有机磷农药－久效磷对海洋微藻的毒性机理进行了研究。结果结果，随着久效磷胁迫时间的延长，3种海洋微藻：扁藻、叉鞭金藻和三角褐指藻细胞的膜脂过氧化产物丙二醛（MDA）含量不断提高，与此同时，3种微藻细胞的电解质外渗率也相应地增加。这说明在久效磷的胁压力下，微藻细胞内过量的活性氧引起细胞膜的膜脂过氧化伤害，导致细胞膜透性增加，电解质大量外渗，微藻细胞严重受害，进而生长受到抑制甚至死亡。