塔里木盆地中高氮天然气的成因及其与天然气聚集的关系

塔里木盆地塔北和塔中地区的海相腐泥型天然气,N2含量较高,尤其是湿气,N2含量分布在10.1％～36.2％,而干气的N2含量则低于10％,即湿气的N2含量高于干气的N2含量。同是下古生界寒武－奥陶系来源的海相腐泥型天然气,为什么湿气和干气的氮气含量相差如此之大?根据与氮气相伴生的烃类气体、非烃气体及稀有气体的组份及同位素特征,认为塔里木盆地的中高氮天然气属于有机成因,来源于下古生界海相烃源岩。文章还提出塔北和塔中地区湿气和干气N2含量差异与源岩的演化程度和圈闭的捕获条件有关。     

松辽盆地徐家围子断陷深层天然气同位素倒转现象研究

天然气的同位素组成受源岩有机质类型、热演化程度和成藏后的次生变化等多种因素的影响, 其单体烃同位素分布特征是区分各种因素影响程度的地球化学指纹.天然气单体烃同位素通常有随碳数增加而变重的趋势, 而徐家围子深层天然气单体烃同位素倒转现象却比较普遍, 高地温和细菌氧化对于造成该区同位素倒转的可能性不大, 浅层油型气或无机气的混合作用没有充分的地质证据, 同层有机质中不同类型气的混合和盖层微渗漏造成的蒸发分馏作用可能是导致徐家围子断陷深层天然气同位素倒转的主要原因.      

Water chemistry of Lake Quilotoa (Ecuador) and assessment of natural hazards

A geochemical survey carried out in November 1993 revealed that Lake Quilotoa was composed by a thin (14 m) oxic epilimnion overlying a 200 m-thick anoxic hypolimnion. Dissolved CO₂ concentrations reached 1000 mg/kg in the lower stratum. Loss of CO₂ from epilimnetic waters, followed by calcite precipitation and a consequent lowering in density, was the apparent cause of the stratification.The Cl, SO₄ and HCO₃ contents of Lake Quilotoa are intermediate between those of acid–SO₄–Cl Crater lakes and those of neutral-HCO₃ Crater lakes, indicating that Lake Quilotoa has a ‘memory’ of the inflow and absorption of HC1- and S-bearing volcanic (magmatic) gases. The Mg/Ca ratios of the lake waters are governed by dissolution of local volcanic rocks or magmas, but K/Na ratios were likely modified by precipitation of alunite, a typical mineral in acid–SO₄–Cl Crater lakes.The constant concentrations of several conservative chemical species from lake surface to lake bottom suggest that physical, chemical and biological processes did not have enough time, after the last overturn, to cause significant changes in the contents of these chemical species. This lapse of time might be relatively large, but it cannot be established on the basis of available data. Besides, the lake may not be close to steady state. Mixing of Lake Quilotoa waters could presently be triggered by either cooling epilimnetic waters by 4°C or providing heat to hypolimnetic waters or by seismic activity.Although Quilotoa lake contains a huge amount of dissolved CO₂ (3×10¹¹ g), at present the risk of a dangerous limnic eruption seems to be nil even though some gas exsolution might occur if deep lake waters were brought to the surface. Carbon dioxide could build up to higher levels in deep waters than at present without any volcanic re-awakening, due to either a large inflow of relatively cool CO₂-rich gases, or possibly a long interval between overturns. Periodical geochemical surveys of Lake Quilotoa are, therefore, recommended.     

20世纪十大灾难性地震(续完)

叙述了２０世纪全球１０次灾难性地震发生的时间、震级、地点、伤亡人数、建筑物遭破坏以及救灾的情况,记述了一些地震的前兆现象和经济损失。     

Study of elastic wave propagation in two-phase anisotropic media by numerical modeling of pseudospectral method

When there exists anisotropy in underground media, elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media, four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.     

地球空间信息科学在湖南国土资源可持续发展中的应用前景雏议

可持续发展是跨世纪多学科综合的重大学科领域,而地球空间信息科学是空间信息科学发展的重要成果。本文在阐述了地球空间信息科学的特点及发展现状,国土资源可持续发展的内涵和特点之后,简要探讨了地球空间信息科学在湖南国土资源可持续发展中的应用前景。     

植物单叶偏振反射特征研究

简明地阐述了植物单叶偏振反射特征以及影响植物单叶偏振反射的主要因素 ,这对偏振光遥感的深入研究具有一定的理论和实践意义     

An Analysis of the Recent Severe Storm Surge Disaster Events in China

The economic loss caused by the storm surgedisasters is much higher than that caused by anyother marine disaster in China, the loss from the severestorm surge disaster being the highest. Statistics showthat there were 62 typhoon landings over the east-southeastcoast of China since 1990, three of which,occurring in 1992, 1994 and 1997, respectively, caused themost severe damage. The direct economic lossesdue to these events are 9.3, 17.0 and 30 billion yuan(RMB, or about 1.7, 2.6 and 3.8 billion USD,respectively), which is much greater than the loss of 5.5billion yuan (RMB) on an average every year duringthe 1989–1991 period. This paper makes a comparativeanalysis of the damage caused by the three events andpresents an overview of progress of precautions againststorm surge disaster in China. The suggestedcounter measures to mitigate the loss from the severe stormsurge disasters in China is as follows: (1) Raisethe whole society awareness of precaution against severestorm surge disaster; (2) Work out a new plan forbuilding sea walls; (3) Improve and perfect the availablewarning and disaster relief command system; (4)Develop the insurance service in order to promptly mitigatethe loss caused by severe storm surge disaster event.     

贵州茂兰喀斯特森林自然保护区的生态旅游

阐述了贵州茂兰喀斯特森林自然保护区开展生态旅游的意义,分析评述了该保护区开展生态旅游的优劣势。针对茂兰喀斯特森林自然保护区生态环境本底脆弱和生态旅游的内涵要求,探讨了在该保护区开展生态旅游应坚持的四条原则,提出了适合茂兰喀斯特森林保护区地域特色的生态旅游开发的方向及相应的对策。      

城市生态环境形象设计的生态背景值研究

城市生态背景值包括自然生态背景值与人文生态背景值。城市生态背景值越高,城市生态环境形象建设与管理的成本就越低。通过城市生态背景值的相关因素分析与量化分等,在选择分析的中国14个特大城市中,生态背景值相差甚远。按综合分值分等,第一等空缺,第二等和第三等分别只有广州市和上海市,第四等有7个城市,第五等有3个城市,得分最低的第六等有兰州市和乌鲁木齐市。按自然生态背景值分值划分,第一等空缺,得分最高的第二等只有广州市,最低的第九等是乌鲁木齐市。按人文生态背景值分值划分,第一等空缺,第二等是北京市,其余为第三等和第四等。文章以城市生态背景值为依据,较为详细地分析了广州市何以在较短的时间内由一个"不适合居住"的城市变为"国际花园城市"的原因。