共查询到20条相似文献，搜索用时 93 毫秒
1.
David Page 《Geology Today》2001,17(4):140-143
The mineralogy, chemistry and stratigraphy of Precambrian banded iron formations have been extensively documented, yet the way such formations are produced remains a subject for debate. Differentiation by varving, microbial precipitation and secondary alteration are all seen as possible mechanisms, but discussion returns to the lack of any modern analogue. Nothing like banded iron forms anywhere in the world today or has done during the entire Phanerozoic. Where do we begin with such enigmatic rocks? 相似文献
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Harald Rosenthal Dr. rer. nat. 《GeoJournal》1985,10(3):305-324
Aquaculture can be considered as a rapidly growing industry in many parts of the world. The impressive overall upward trend in production is likely to continue for the rest of the century. However, aquaculture will still be a minor contributor to the world's protein supply, even though the projected annual output of about 30 million tons can be realized by the year 2000. Nevertheless, aquaculture can play an important role in many developing countries not only within the context of rural development, but also as a commercial activity that focuses on export markets. Progress in aquaculture will always be accompanied by a number of constraints that occur with or through expansion of this industry. Some of the most important problem areas are briefly addressed, including those related to environmental degradation, disease control, human health and competition for resources. Finally, gaps in science and technology as well as research priorities are identified. 相似文献
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我国北方干旱化研究——面向国家需求的全球变化科学问题 总被引：44，自引：0，他引：44
近几十年来 ,全球环境变化已经成为国际社会关注的焦点。中国也面临一系列与此相关的重大生存环境问题。其中最为突出的是北方地区的干旱化。其主要表现为 :降水量减少 ,雪线高度抬升 ,湖泊萎缩 ,河网干枯 (特别如黄河断流 ) ,土地荒漠化 ,生态系统退化等等。这些问题已经成为国民经济发展的严重障碍。北方干旱化是怎样形成的 ?其未来发展趋势如何 ?将对中国的生存环境和社会经济可持续发展产生什么影响 ,应采取什么对策 ?政府和公众迫切要求回答这些与社会发展和人民生活密切相关的重大问题。文中分析了北方干旱化问题的性质 ,提出了面对国家需求应解决的关键科学问题和主要研究内容 ,简要介绍了在国家重点基础研究规划项目的支持下 ,近年来的主要研究进展 ,其中包括北方地区不同时间尺度干湿变化的规律和干旱化的证据 ,全球增暖和人类活动 (主要是水土资源的利用 )对干旱化的影响 ,主要生态系统对干旱化的响应和适应以及组织有序人类活动 ,改善生态环境 ,缓解干旱化影响的虚拟试验的结果等。 相似文献
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A partial instructional module on global and regional land use/cover change: assessing the data and searching for general relationships 总被引：4，自引：0，他引：4
Susanne C. Moser 《GeoJournal》1996,39(3):241-283
Land use/cover change has occurred at all times in all parts of the world. Most affected and involved in these processes are the environmental spheres of water, soil, and vegetative cover, which are closely linked to geomorphology, climate, fauna, and especially human societies. These linkages between spheres are highly complex and, as of yet, incompletely understood. The most profound questions with respect to land use/cover and global change are: “What forces drive land use/land cover change?”, “What impacts — direct and indirect, now and in the future — do these changes have on the environment and on human society?” and “Can and should we, and if so, how, respond to these changes?” This partial teaching module, developed under the auspices of the Second Commission on College Geography of the Association of American Geographers, introduces students to the complexities inherent in these questions, but mainly focusses on the first of these. It illustrates the central role of the study of land land use/cover change within the large field of global environmental and climatic change, and is thus a good unit to introduce this area of interest. 相似文献
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Assessment of land degradation east of the Nile Delta, Egypt using remote sensing and GIS techniques 总被引：1，自引：0，他引：1
Land degradation is one of the most common issues in the eastern part of the Nile Delta area that threatens the ongoing agricultural activities and prohibits further reclamation expansions. The different degradation types and the associated risk assessment of some soils types of western Suez Canal region during the period from 1997 to 2010 is discussed. The assessment of the different degradation degrees in the investigated area has been carried out through integrating remote sensing, GIS and GLASOD approaches. Results revealed that the salinization, alkalization, soil compaction and water logging are the main types of land degradation in the area. The main causative factors of human induced land degradation types are; over irrigation, human intervention in natural drainage, improper time use of heavy machinery and the absence of conservation measurements. Low and moderately clay flats, gypsifferous flats, have high to very high risk in both salinization sodication and physical degradation. Values such as EC, ESP, and ground water level reach 104.0 dS/m, 176? % and 60 cm, respectively. These results will be of great help and be basic sources for the planners and decision makers in sustainable planning. The spatial land degradation model was developed based on integration between remote sensing data, geographic information system, soil characteristics and DEM. 相似文献
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确定大江大河防洪堤高度应考虑地面沉降因素——对1998中国大洪水的反思 总被引：8，自引：0，他引：8
世界上抽汲地下水或石油引起地面沉降正越来越普遍。大江大河防洪能力降低是地面沉降灾害现象之一。上海因地面沉降产生严重的洪涝灾害,上海外滩防汛墙高度的主要决定因素是地面沉降。沙市、武汉、哈尔滨和大庆等城市和地区是我国1998年夏特大洪水的重灾地区,这些城市和地区实际上已存在地面沉降问题。几十年来产生的地面沉降很可能已降低了这些地区江河大堤的防洪能力,从而加重了这次洪涝灾害。建议在确定大江大河防洪堤高度应考虑地面沉降因素,并尽快对重点城市和地区进行地面沉降调查与预测研究。 相似文献
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Population growth and land degradation 总被引：2，自引：0，他引：2
Mortimore M 《GeoJournal》1993,31(1):15-21
The author examines the relationship between population growth and land degradation in the developing world. The focus is on the process of desertification in arid regions. 相似文献
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《International Geology Review》2012,54(8):1480-1486
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W. S. Fyfe 《Engineering Geology》1999,52(3-4):159-161
The isolation of nuclear wastes for at least thousands of years is an urgent world problem. It is an international problem, for in many nations with such wastes their geology is not suitable for long-term isolation.
A lead geo-question involves which are the best host rocks, with guaranteed long-term low permeability and the best ion-exchange, redox systems for the capture, retention, of the most dangerous nuclides. In general mud rocks on land or the sea floor must be considered. 相似文献
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Ana María Fernández-Maldonado 《Geoforum》2008,(6):1884-1896
In many cities of the developing world, poor residents occupy land and build their dwellings before infrastructure is provided. Expanding the infrastructure networks for the poor is a long, expensive and complicated affair. Before the 1990s, the public sector was generally in charge of the basic services; but these services have been liberalized and, in many cases, privatized since then. In this new context, a relevant question is: have these reforms contributed to urban integration? Or, on the contrary, have they contributed to deepen urban fragmentation? This study presents the case of water and telecommunications services in Lima, Peru, the most contested and politically sensitive urban sectors. The objective is to test Graham and Marvin’s claims about the splintering of networked infrastructures expressed in Splintering Urbanism.The findings show that the reforms have improved the situation at aggregate level, but there is still no sustainable solution for the crucial dilemma of cities with high poverty restrictions: self-financed network expansions versus service affordability. The diverging paths of the utilities reform in Lima illustrate that privatization is not the main issue in the discussion to expand the networks for the poor. The main conclusion is that sensible policies complemented with carefully targeted subsidies and continuous regulation can successfully provide water for all. Good governance practices at the urban level help to achieve this goal. Water and telecommunications in Lima also show that are no general solutions for the universalization of the services; each city is different and some sectors are much more complex and problematic than others. This demands careful and continuous technical and political consideration of the local circumstances to reform the utilities. 相似文献
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日益发展的垃圾回收业 总被引：1，自引：0，他引：1
垃圾中蕴藏着许多可供人类开发利用的物质和能量，回收利用垃圾资源正日益受到世界各国的普遍重视。通过对国外一些国家垃圾回收业发展状况的介绍，提出发展我国垃圾回收业的几点建议。 相似文献
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天津市地下水开采对地面沉降影响的多元回归分析 总被引：1，自引：0，他引：1
地下水的过量开采是天津市引起地面沉降的主要原因。因此天津市提出了“压缩地下水开采量”、“地下水人工回灌”、“调整地下水开采层次”等控制地面沉降的3大技术措施。经过多年的努力,控制地面沉降效果明显。如何解决地下水开发与控制地面沉降的关系,更好的贯彻这3大技术措施,是该文编写的初衷。即在开采同样地下水量的情况下,如何使地面沉降量最小;或在地面沉降量容许的情况下,如何开采最大量的地下水。压缩地下水开采量是治理地面沉降的根本措施,亦即如何压缩采水量或调整开采层次会达到最好效果。论文对天津市某区各个地下水开采层的多年累计开采量、累计沉降量进行数据统计分析,建立了该地区累计沉降量及各个地下水开采层的多元相关方程。在此基础上,分析了各个地下水开采层对地面沉降影响的相关程度。以此为该区控制地面沉降的提供依据。 相似文献
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世界和中国的冰川分布及其水资源意义 总被引：15，自引：5，他引：10
世界上巨大数量的冰川是优质清洁的淡水资源,但分布极其不均衡,导致在各地区可利用价值的差异.冰盖全部集中在南极和格陵兰,山岳冰川的84%集中于亚洲高地和北美寒区.中国是中低纬带冰川最多规模最大的国家,又是世界荒漠区和贫水国中冰川最多的国家.中国冰川分布以青新荒漠绿洲区最多,其中塔里木是世界上冰川最多的内流水系,并哺育出塔里木冰水绿洲.为平衡绿洲经济发展与生态环境安全的关系,提出"养源平流"方针. 相似文献
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We deal with a multi-parameter identification problem arising in oil industry. In the general case, we give a local solvability condition to guarantee the well-posedness of the problem. We discuss in detail the identification of two parameters for which some numerical results are given. 相似文献
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Land degradation in the source region of the Yellow River, northeast Qinghai-Xizang Plateau: classification and evaluation 总被引：6，自引：0，他引：6
Land degradation imposes a great threat to the world. It is not merely an environmental issue, but also a social and economic problem. Land desertification is among the main aspects of environment changes in the source region of the Yellow River. Previous studies focused on water resource utilization and soil erosion, but land degradation in the source region of the Yellow River even the whole Qinghai-Xizang Plateau received little attention. Based on the data obtained by field investigation and TM satellite images of 2000, this study provides the classification and evaluation information of the land degradation in the source region of the Yellow River. There are six types of land degradation in this region: water erosion in the northern mountains around the Gonghe Basin, sandy desertification in the Gonghe Basin and Upland Plain Area, aridization in the lower reaches, salinization in the Gonghe Basin, vegetation degradation in the intramontance basin and freezing and thawing erosion in the high mountains. The total degraded area is 34,429.6 km2, making up 37.5% of the land in the study area. Finally, land degradation in the source region of the Yellow River was evaluated according to changes in the physical structure and chemical component of soils, land productivity, secondary soil salt and water conditions. 相似文献
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We deal with a multi-parameter identification problem arising in oil industry. In the general case, we give a local solvability condition to guarantee the well-posedness of the problem. We discuss in detail the identification of two parameters for which some numerical results are given. 相似文献
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贵州省喀斯特地区土地退化与生态重建研究进展 总被引：60，自引：2，他引：60
喀斯特地区环境独特、生态脆弱，一直是科学界关注的热点地区。早期的研究多集中在喀斯特地区的水文、地质和地球化学等领域。近10多年来，喀斯特地区的土地退化乃至石漠化的问题日益严重，人类活动对生态的压力逐渐成为人们关注的焦点。我国西南喀斯特地区是世界上最大的喀斯特连续带，贫困人口集中，人口压力大，经济落后，土地退化严重，人地矛盾异常尖锐，如何开展生态建设、促进社会经济发展，成为西部大开发中最为紧迫的任务之一。贵州省是西南喀斯特地区的典型代表，部分地区已经失去了依靠自身力量进行生态恢复和发展的可能性，因而需要在科学研究的基础上，制定合理的规划和管理措施，针对性的增加外部投入，进行生态重建。对生态重建的理论、方法、技术和模式进行了总结，认为喀斯特地区土地退化是区域人地复杂巨系统结构损害和功能紊乱的集中表现，片面的环境保护和单独的生态治理工程无法解决这个系统问题，区域的生态重建需要采用系统科学的思路。在此基础上，提出喀斯特地区土地退化和生态重建研究中需要深入研究的一些问题。 相似文献