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1.
Heath J. Carney Mark C. Whiting Katharine E. Duff Donald R. Whitehead 《Journal of Paleolimnology》1992,7(1):73-94
Thirty-three lakes in the Sierra Nevada range of California were investigated as part of a paleoecological study of the potential effects of acid deposition on sensitive lake/watershed ecosystems. Chrysophyte cysts from surface sediment samples were analyzed and compared with data on pH and alkalinity. This paper identifies the twenty-five dominant chrysophyte cyst taxa and provides information on their morphology, abundance, distribution and ecology.Chrysophycean cysts were generally abundant and well-preserved in lake sediments of our study sites. Twelve taxa occurred in more than twenty of the thirty-three lakes; these taxa were often quite abundant. In contrast, only nine taxa occurred in ten or fewer lakes. Abundance Weighted Mean (AWM) pH varied from 6.45 to 8.34 and AWM alkalinity varied from 46 to 588 eq/L. We delineated pH preference categories, based on AWM pH values and frequency diagrams of cyst abundance vs. lake-water pH. We classified five taxa as acidophilous, nine as circumneutrals, six as alkaliphilous and five as indifferent. Given that the cyst types differ greatly in their abundance relative to pH and alkalinity, it is clear that they have potential for paleolimnological studies of Sierra lakes biogeochemistry. 相似文献
2.
Fenda A. Akiwumi 《Singapore journal of tropical geography》2011,32(1):53-70
This paper draws from world‐systems and sustainable livelihoods approaches to analyze the connections between multinational exports of rutile (titanium oxide), diminished ecological resources and resource‐based livelihoods, and gendered household dynamics in a peripheralized mining region in Sierra Leone. The discussion focuses on how the extraction of mineral resources instigated by exogenous capital investors forces links to household transformation, particularly the vulnerability context of women. Using archival records and field survey data, the case study of rutile mining in southwestern Sierra Leone connects the low‐waged mining labour of traditional resource‐based subsistence communities and deepening marginalization of and financial pressures on women in mining households to global mineral markets. The study focuses on women's coping mechanisms that are embedded within traditional social networks in relation to an external intervention, a low‐tech mechanical cassava grater, intended to strengthen their livelihoods. It finds that the potential for this transformation is impeded by sociocultural, environmental and financial limitations. 相似文献
3.
In Ethiopia and Sierra Leone, recent social, political and environmental transformations have precipitated the intensification of wetland use, as local people have sought to safeguard and strengthen their livelihoods. Concurrent decentralization policies in both countries have also seen the government strengthen its position at the local level. Drawing upon recent field-based evidence from Ethiopia and Sierra Leone, this paper examines the compatibility between community-based local institutions for wetland use, and the process of decentralization. It argues that decentralization has in fact restricted the development of mature local institutional arrangements, due to its intrinsically political interventionist nature. 相似文献
4.
Increasingly stringent regulatory regimes, in conjunction with landfill development in environmentally sensitive locations and the large number of abandoned landfill sites, are significantly increasing the responsibilities of local authorities and environmental agencies. These responsibilities include the identification and/or monitoring of: locations of contaminated land; boundaries of waste sites; nature of the landfill content; location, extent, content and depth of closed landfill sites; leachate plumes escaping from both operational and closed sites and the performance of landfill liners. Probabilistic risk based modelling is a standard methodology for monitoring and managing the environmental impact of landfill sites. A critical problem in the implementation of probabilistic risk based modelling is the large uncertainty in the shallow geology, internal structure and leachate distribution of landfills caused by the severe lack of both surface and subsurface information from within and outside the landfill site. The utility of two non-invasive ground based geophysical monitoring techniques, ground penetrating radar and reflectance spectroscopy, as aids to characterising the three-dimensional structure and distribution of leachate within a landfill has been investigated. Strong correlations between red edge inflection position and chlorophyll and metal concentration have been demonstrated from grassland species affected by leachate contamination of the soil adjacent to the landfill study site. The results of this study have demonstrated how recent advances in equipment, techniques and software mean that field-based reflectance spectroscopy and Ground Penetrating Radar can now provide environmental scientists with cost-effective, rapid techniques to characterise landfill sites in three dimensions, aid landfill managers in positioning additional boreholes and field sampling surveys, and provide data as inputs to leachate migration modelling. 相似文献
5.
A demographic and spatial analysis of mortality in Freetown, Sierra Leone, is presented, with emphasis on data for the census years 1963 and 1974. Consideration is first given to the availability of data and their quality. The authors then examine geographic variations in mortality within the city, age- and sex-specific death rates, the major causes of death, and death certification. 相似文献
6.
Late orogenic intramontane basin development: the Granada basin, Betics (southern Spain) 总被引：2，自引：0，他引：2
The quantitative study of subsidence in the Granada basin, using decompaction and backstripping techniques, and contemporaneous relief development in the surrounding areas, especially in the Sierra Nevada, provides a good case example of the development of an intramontane basin. In the Granada basin, according to the interpretation of the seismic profiles and results of the backstripping analysis, subsidence and sedimentation rates were at a maximum in the late Tortonian and decreased progressively; meanwhile, the neighbouring areas were uplifted forming important relief. Chronostratigraphical revisions of the marine sediments show that the marine incursion that deposited sediments in the Granada basin lasted only 1.3 Ma, between 8.5 and 7.2 Ma. The gradual retreat of the sea in the Granada basin is not attributable to global eustatic fluctuations, but rather to uplift in the Sierra Nevada and its adjacent areas. From latest Tortonian to early Messinian times, the region became continental and the Granada basin acquired its present physiography and was differentiated as such. From the late Tortonian onwards, NNW–SSE compression combined with ENE–WSW extension affected the cordillera. In the Granada basin, extension controlled fault movements. There are two well-defined fault sets: the first trends 70°N–90°E, with low angle faults (less than 30°) dipping towards the north and south, defining the subsiding areas which have approximately E–W direction; whereas the second set has a NW–SE direction, and cuts and displaces the previous ones, defining the main subsiding areas in the eastern part of the basin. The reinterpretation of seismic profiles reveals that the subsiding axes within the Granada basin persisted from the Tortonian to the present because of continued displacements of the main faults. 相似文献
7.
Marcus Power 《Area》2000,32(1):91-100
Summary Under New Labour, the British Department for International Development (DFID) promises a radical and alternative new 'development agenda' and, more specifically, an end to 'development handouts'. The short cut to international development envisioned by Secretary of State Clare Short is explored in this paper, as is the 'messy' contextuality of writing about development in 'New Britain'. This paper raises questions about New Labour's discussion of the 'moral authority' for international development in 'post-colonial' Britain, particularly in light of the recent 'arms-to-Africa' affair involving Britain and Sierra Leone. The paper argues that Britannia's neoliberal vision of development is not so 'cool' and that, in ethical terms, the development of foreign policy toward Africa has not been consistent. In conclusion, the paper raises doubts about the likelihood of world poverty being halved by 2015 (as the DFID has confidently predicted). 相似文献
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There has been a notable increase in the use of geographic information systems (GIS) in studies of environmental (in)justice in the last two decades. Whilst the potential of such techniques is increasingly being recognised, there remain some key research challenges facing researchers interested in wider notions of environmental justice (EJ). One avenue of research concerns the estimation of population denominator and the influence of the estimation model on the conclusions emanating from such studies. Whilst the potential of so-called dasymetric mapping techniques have been explored in other substantive areas such as crime and health geography, their use in EJ applications remains under-explored. This paper represents a preliminary attempt to redress this gap in the literature through a comparison of the deprivation profiles of residents living in the vicinity of landfill sites in Wales using both ‘traditional’ and innovative methods of population estimation that provide a more realistic representation of actual population distribution. The results as we demonstrate suggest that more emphasis needs to be placed on the methods by which population is estimated if the results of GIS-based environmental justice studies are to be more widely applied. 相似文献
10.
AMENITY MIGRATION IN THE U.S. SIERRA NEVADA* 总被引：1，自引：0，他引：1
ABSTRACT. Since 1960 California's Sierra Nevada counties have ranked among the regions with the strongest relative population growth in the state. Reassessment of peripheral areas has been the main force driving population and settlement growth in the central Sierra Nevada of California and Nevada, termed “amenity migration” or “counterurbanization.” This study analyzes the impacts of amenity migrants—“urban refugees”—on socioeconomic conditions in high‐mountain regions. We define these regions as the “High Sierra,” comprising zones at elevations more than 1,800 meters above sea level. People who migrate to the High Sierra tend to be white and well educated, with considerable household earnings. Unlike the population in the foothills, these migrants are not senior citizens. Their demand for periodic or permanent residences has caused housing prices to increase enormously. As a result, a majority of homes are now priced well beyond the reach of local salaries, which may lead to potential conflict between locals and newcomers. The massive settlement expansion in high‐mountain areas requires a new approach to land‐use planning, one that takes functional regions into account. Therefore, it is expedient to reassess existing jurisdictional boundaries. 相似文献
11.
Temporal patterns in floodplain genesis and alluvial sedimentation in lowlands tropical rain forest zones of Ghana, Sierra Leone and western Kalimantan (Indonesian Borneo) based upon 14C age determinations are described.Alluvial low terraces or buried sediments in West Africa yielded ages of 36-21 ka. In west Kalimantan a widespread episode of alluviation has yielded dates of 54-51 ka. The 20-13 ka interval was characterised by channel incision with valley floor erosion and neither region records sedimentation. Holocene alluvial sedimentation and floodplain construction in West Africa occurred during two temporal intervals: 10-7 ka and 4 ka to present and in western Kalimantan in response to early Holocene sea level rise followed by late Holocene regression and coastal outgrowth.The clustering of 14C dates closely corresponds to regional lake level fluctuations and vegetational changes and to global indications of climatic change. We propose that periods of more frequent episodes of accelerated floodplain erosion and reconstitution, channel morpho-sedimentary activity and alluvial accumulation (1) are responses to interstadial and interglacial periods of higher precipitation following intervening periods of cooler and drier conditions; and (2) may be synchronous during the last 60 ka throughout the African and Asian inner humid lowland tropics. 相似文献
12.
Testing the sensitivity of geomorphic indices in areas of low-rate active folding (eastern Betic Cordillera, Spain) 总被引：2，自引：0，他引：2
Antonio Pedrera Jos Vicente Prez-Pea Jesús Galindo-Zaldívar Jos Miguel Azan Antonio Azor 《Geomorphology》2009,105(3-4):218-231
Active deformation structures have an incidence in topography that can be quantified by using geomorphic indices. Most of these indices have been checked in faulted regions with high-deformation rates. The application of several geomorphic indices (hypsometric curve analysis, normalized stream-length gradient, and valley width-to-valley height ratio) to the drainage network of the southern limb of the Sierra de Las Estancias antiform (Internal Zones, eastern Betic Cordillera), where low-rate active folding has been recognized, allows us to investigate the suitability of these indices to identify active structures in such a scenario. Hypsometric curves clearly identify regions with recent uplift and young topography, but they do not provide any constraint on the location of active folds. Local valley width-to-valley height index variations have been detected just coinciding whit the position of ENE–WSW active folds. Normalized stream-length gradient index serves to locate active folds in areas of hard rock substratum, but not in those areas with soft sediments (Neogene-Quaternary sedimentary basins). This is most likely due to the fact that in the basins erosion is much more intense than in the hard rock sectors. In view of these results, we consider that geomorphic indices constitute a valuable tool for identifying sectors affected by low-rate uplift related to active folding, with the best results obtained in hard rock areas. 相似文献
13.
Sierra Leone has recently emerged from a long period of political instability and is ranked among the world's poorest countries. During the decade-long civil war of the 1990s, widespread forced out-migration left much of the countryside abandoned, as rural residents fled to the safety of the capital city, Freetown. Consequently, food production became severely dislocated and, in the post-conflict era, the state of the agricultural sector has become a major concern to governmental and non-governmental development agencies. Focussing on the question of urban food security in Freetown, this paper examines the incidence, dynamics and significance of urban and peri-urban agriculture (UPA) among households, at a crucial point in Sierra Leone's post-conflict reconstruction phase. Drawing on recent field-based data, the paper contributes to the growing debate concerning how urban planning and development might be reconciled with the promotion of an ‘enabling environment’ in which UPA is encouraged and supported. It is argued that in the case of Freetown, a detailed evaluation of UPA is urgently needed to determine how agricultural activities can fit in with urban structure, urban problems and the livelihoods of a wide range of actors in and around the city. The paper concludes that not only is UPA a vital element in ensuring household food security, but it could potentially play a fundamental role in safeguarding the urban food continuum and promoting sustainable urbanization in the post-conflict period and beyond. 相似文献
14.
Municipal Solid Waste (MSW) landfills world-wide are experiencing the consequences of conventional landfilling techniques, whereby anaerobic conditions are created within the landfill waste. Under anaerobic conditions, slow stabilization of the waste mass occurs, producing methane, (an explosive, 'greenhouse' gas) and toxic leachate over long periods of time. As a potential solution, it was demonstrated that the aerobic degradation of MSW within a landfill can significantly increase the rate of waste decomposition and settlement, decrease the production of methane gas, reduce the level of toxic organics in the leachate and decrease quantities of landfill leachate that need treatment. This paper summarizes the successful results of two separate aerobic landfill projects located in Georgia (USA) and discusses the potential economic and environmental impacts to world-wide solid waste management. 相似文献
15.
With Globally Important Agricultural Heritage Systems (GIAHS) increasing in number around the world, their conservation has become a new international research theme. From the perspective of combining theoretical analyses and practical case applications, this study examines the Important Agricultural Heritage Systems (IAHS) conservation pathways and operation mechanisms through industrial integration development (IID). First, the theoretical framework of IID in IAHS sites was constructed according to the requirements of IAHS conservation, which include analyses of the connotation and basic principles of IID, the necessity of IID for IAHS sites, the resource conditions, and the IID pathways. And then based on the theoretical framework, the IID of Longji Terraces in Guangxi, Honghe Hani Rice Terraces System in Yunnan (HHRTS), Aohan Dryland Farming System in Inner Mongolia (ADFS), and Huzhou Mulberry-dyke & Fish-pond System (HMFS) in Zhejiang are analyzed systematically. The main finding is that IID is an effective pathway for IAHS conservation. However, the IID in IAHS sites must stress the ecological and cultural values of the resources; IID should be based on local resource advantages; and IID should attach importance to the combination of different policies and coordination between different stakeholders. 相似文献
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17.
巢湖西湖岸新石器-商周遗址空间分布规律及其成因 总被引：2，自引：0，他引：2
将地理信息系统空间分析方法引入巢湖西湖岸新石器-商周遗址考古工作,通过点密度分析、空间距离分析、三维分析、缓冲区分析等方法研究遗址空间分布规律及其影响因素。研究表明自新石器至商周时期研究区内遗址时空分布呈现:随时间推移由湖岸边逐渐向西北部扩展,后迁移至南部,再均匀扩散的遗址迁移轨迹;先民多选择靠近水源、地势平坦、土壤肥沃的自然岗地、河谷阶地、山麓面居住,导致古遗址空间上大致呈线状、团聚状、分散状等分布特征,具有明显的河谷谷地指向性、阶地岗地指向性、土壤指向性等规律。提出遗址分布在早期可能主要受到气候水文、地貌、植被土壤等自然因素影响,后期生产力发展水平、经济生活方式等人文因素影响加重。本研究为GIS支持下区域考古研究提供了合适的研究实例,同时GIS方法得到一些推论假设仍需要田野考古调查与发掘等进一步佐证。 相似文献
18.
Sierra Nevada is a protected mountain in the Iberian Peninsula classified as a Biosphere Reserve (1986), Natural Park (1989) and National Park (1999). All these environmental protection programmers are a consequence of its unique landscape in the context of the mid-latitude semiarid mountains, with enclaves of exceptional scientific and cultural value. Thanks to its high altitude, Sierra Nevada held the southernmost Quaternary glaciers in Europe, as well as it happened during the Little Ice Age. In turn, Sierra Nevada is also singular thanks to its vast cultural heritage, since very early societies settled on its slopes and valleys and accommodate their lifestyles and economy to the characteristics of this mountain environment. Currently, Sierra Nevada has become an important tourist centre and receives a large amount of visitors. This process of change has conditioned the implementation of a different economic model: it brings benefits to the populations but it involves changes in the landscape as well, sometimes questionable. From this perspective, a critical revision of the legislation is required balancing the sustainable economic development of the population and the preservation and safeguarding of the heritage values of the landscape. With this goal, we suggest creating and implementing the Sites of Geomorphological Interest. 相似文献
19.
A continental sequence of red beds and interbedded basaltic layers crops out in the Sierra Chica of Córdoba Province, Argentina (31.5°S, 64.4°W). This succession was deposited in a half-graben basin during the Early Cretaceous. We have carried out a palaeomagnetic survey on outcrops of this basin (147 sites in seven localities). From an analysis of IRM acquisition curves and detailed demagnetization behaviour, three different magnetic components are identified in the volcanic rocks: components A, B and X are carried by single- or pseudo-single-domain (titano) magnetite, haematite and multidomain magnetite, respectively. Component A is interpreted as a primary component of magnetization because it passes conglomerate, contact, tilt and reversal tests. The carrier of the primary magnetization, fine-grained (titano)magnetite, is present in basalts with a high degree of deuteric oxidation. This kind of oxidation is interpreted to have occurred during cooling. Components B and X are discarded because they are interpreted as recent magnetizations. In the sedimentary rocks, haematite and magnetite are identified as the carriers of remanence. Both minerals carry the same component, which passes a reversal test. The calculated palaeomagnetic pole, based on 55 sites, is Lat. 86.0°S, Long. 75.9°E ( A 95 =3.3, K =35). This palaeomagnetic pole supersedes four with anomalous positions reported in previous papers. 相似文献
20.
The Global Rainforest Mapping (GRFM) project was initiated in 1995 and, through a dedicated data acquisition policy by the
National Space Development Agency of Japan (NASDA), data acquisitions could be completed within a 1.5-year period, resulting
in a spatially and temporally homogeneous coverage to contain the entire Amazon Basin from the Atlantic to the Pacific; Central
America up to the Yucatan Peninsular in Mexico; equatorial Africa from Madagascar and Kenya in the east to Sierra Leone in
the west; and Southeast Asia, including Papua New Guinea. To some extent, GRFM project is an international endeavor led by
NASDA, with the goal of producing spatially and temporally contiguous Synthetic Aperture Radar (SAR) data sets over the tropical
belt on the Earth by use of the JERS-1 L-band SAR, through the generation of semi-continental, 100m resolution, image mosaics.
The GRFM project relies on extensive collaboration with the National Aeronautics and Space Administration (NASA), the Joint
Research Center of the European Commission (JRC) and the Japanese Ministry of International Trade and Industry (MITI) for
data acquisition, processing, validation and product generation. A science program is underway in parallel with product generation.
This involves the agencies mentioned above, as well as a large number of international organizations, universities and individuals
to perform field activities and data analysis at different levels. 相似文献