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21.
Since a state law issued in 1989, every big town in Colombia has to promote its own preparedness programme for disaster relief in the framework of the Oficina Nacional para la Atencion de Desastres (1987). Such a programme includes a very detailed hazard-zone map for flooding and debris flows in the densely inhabited suburbs of Ibagué city (capital of Tolima Department), as well as enquiries about risk knowledge and consciousness among people who live at high risk. We stress the fact that both detailed hazard-zone maps and enquiries should be closely undertaken at the same time, and that distinguishing previous knowledge, existing consciousness and risk perception to forecast the behaviour of people and of the community in case of disaster, are criteria for a better risk assessment. 相似文献
22.
On the role of heat flow, lithosphere thickness and lithosphere density on gravitational potential stresses 总被引:1,自引:0,他引:1
Gravitational potential stresses (GPSt) are known to play a first-order role in the state of stress of the Earth's lithosphere. Previous studies focussed mainly on crust elevation and structure and little attention has been paid to modelling GPSt using realistic lithospheric structures. The aim of the present contribution is to quantify gravitational potential energies and stresses associated with stable lithospheric domains. In order to model realistic lithosphere structures, a wide variety of data are considered: surface heat flow, chemical depletion of mantle lithosphere, crustal thickness and elevation. A numerical method is presented which involves classical steady-state heat equations to derive lithosphere thickness, geotherm and density distribution, but additionally requires the studied lithosphere to be isostatically compensated at its base. The impact of varying surface and crustal heat flow, topography, Moho depth and crust density on the signs and magnitudes of predicted GPSt is systematically explored. In clear contrast with what is assumed in most previous studies, modelling results show that the density structure of the mantle lithosphere has a significant impact on the value of the predicted GPSt, in particular in the case of thick lithospheres. Using independent information from the literature, the method was applied to get insights in the state of stress of continental domains with contrasting tectono-thermal ages. The modelling results suggest that in the absence of tectonic stresses Phanerozoic and Proterozoic lithospheres are spontaneously submitted to compression whereas Archean lithospheres are in a neutral to slightly tensile stress state. These findings are in general in good agreement with global stress measurements and observed geoid undulations. 相似文献
23.
D. Traor A. Beauvais T. Aug F. Chabaux J.-C. Parisot M. Cathelineau C. Peiffert F. Colin 《Journal of Geochemical Exploration》2006,88(1-3):350
Eluvial concentration of platinum-group minerals (PGM) has developed in the south of New Caledonia, from the weathering of a mafic and ultramafic cumulate. The platinum/palladium (Pt/Pd) ratio evolution from the bottom to the top of the weathering profile indicates a chemical mobilization of Pd in supergene environment. The examination by scanning electron microscopy of the residual PGM collected in the weathering profile and their chemical characterization by electronic microprobe show a preservation of the structure and chemical signature (in the core of the grains) of the fresh PGM. This clearly demonstrates that the PGM studied here are residual and are affected by dissolution process. 相似文献
24.
Miriam Borba-Roschel Anne Alexandre Anglica Fortes Drummond Chicarino Varajo Jean Dominique Meunier Csar Augusto Chicarino Varajo Fabrice Colin 《Journal of Geochemical Exploration》2006,88(1-3):172
This paper presents the preliminary results of phytolith analyses of a peat located in the cerrado of the Uberaba municipality, State of Minas Gerais, Brazil. The phytolith soil sequence is discussed by comparison with phytolith assemblages extracted from dominant plants (Cyperaceae and Poaceae). Increasing mean age of phytolith assemblages with depth is assumed. Poaceae Cuneiform bulliform cell, Parallelepiped bulliform cell and Elongate smooth long cell types dominate up to 80 cm, rapidly drop to 42% at 80 cm and regularly decrease from 42% to 2% upwards. Cyperaceae Rondel concave type shows the inverse trend, being dominant in the upper part of the profile. This pattern can be assigned to increasing selective dissolution of the Cyperaceae phytolith type with depth, or/and to a decrease of water stress suffered by the grasses, leading to a decrease of bulliform cell silicification. Soil processes and paleo-environmental changes hypotheses are discussed. 相似文献
25.
Colin McLeay 《GeoJournal》2006,65(1-2):91-102
In the 1990s the artistic autonomy of the territorial subsidiaries of the major record companies increased. Local scale “cultural freedom” did not mitigate the role of national regulation, with the music industry remaining bound by regulation imposed by agencies representing nation-states. National-scale policy rhetoric highlighting the need for “cultural protection” focused attention away from an interest in the economics of popular music, a balance evident in policies of Australian federal governments. In seeking to increase the export potential of locally produced music, Australian governments have come to hold an important place in the political economy of contemporary Australian music. 相似文献
26.
27.
Adrian Lawrence Marianne Stuart Colin Cheney Neil Jones Richard Moss 《Hydrogeology Journal》2006,14(8):1470-1482
Contaminant migration behaviour in the unsaturated zone of a fractured porous aquifer is discussed in the context of a study site in Cheshire, UK. The site is situated on gently dipping sandstones, adjacent to a linear lagoon historically used to dispose of industrial wastes containing chlorinated solvents. Two cores of more than 100 m length were recovered and measurements of chlorinated hydrocarbons (CHCs), inorganic chemistry, lithology, fracturing and aquifer properties were made. The results show that selecting an appropriate vertical sampling density is crucial both to providing an understanding of contaminant pathways and distinguishing whether CHCs are present in the aqueous or non-aqueous phase. The spacing of such sampling should be on a similar scale to the heterogeneity that controls water and contaminant movement. For some sections of the Permo-Triassic aquifer, significant changes in lithology and permeability occur over vertical distances of less than 1 m and samples need to be collected at this interval, otherwise considerable resolution is lost, potentially leading to erroneous interpretation of data. At this site, although CHC concentrations were high, the consistent ratio of the two main components of the plume (tetrachloroethene and trichloroethene) provided evidence of movement in the aqueous phase rather than in dense non-aqueous phase liquid (DNAPL). 相似文献
28.
Yang Liu Alfred T. Anderson Colin J. N. Wilson Andrew M. Davis Ian M. Steele 《Contributions to Mineralogy and Petrology》2006,151(1):71-87
Large pyroclastic rhyolites are snapshots of evolving magma bodies, and preserved in their eruptive pyroclasts is a record
of evolution up to the time of eruption. Here we focus on the conditions and processes in the Oruanui magma that erupted at
26.5 ka from Taupo Volcano, New Zealand. The 530 km3 (void-free) of material erupted in the Oruanui event is comparable in size to the Bishop Tuff in California, but differs
in that rhyolitic pumice and glass compositions, although variable, did not change systematically with eruption order. We
measured the concentrations of H2O, CO2 and major and trace elements in zoned phenocrysts and melt inclusions from individual pumice clasts covering the range from
early to late erupted units. We also used cathodoluminescence imaging to infer growth histories of quartz phenocrysts. For
quartz-hosted inclusions, we studied both fully enclosed melt inclusions and reentrants (connecting to host melt through a
small opening). The textures and compositions of inclusions and phenocrysts reflect complex pre-eruptive processes of incomplete
assimilation/partial melting, crystallization differentiation, magma mixing and gas saturation. ‘Restitic’ quartz occurs in
seven of eight pumice clasts studied. Variations in dissolved H2O and CO2 in quartz-hosted melt inclusions reflect gas saturation in the Oruanui magma and crystallization depths of ∼3.5–7 km. Based
on variations of dissolved H2O and CO2 in reentrants, the amount of exsolved gas at the beginning of eruption increased with depth, corresponding to decreasing
density with depth. Pre-eruptive mixing of magma with varying gas content implies variations in magma bulk density that would
have driven convective mixing.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
29.
Validation of a fish farm waste resuspension model by use of a particulate tracer discharged from a point source in a coastal environment 总被引:2,自引:0,他引:2
Chris J. Cromey Thom D. Nickell Kenneth D. Black Paul G. Provost Colin R. Griffiths 《Estuaries and Coasts》2002,25(5):916-929
To validate a resuspension model of particulate material (salmonid farm wastes), a UV fluorescent particle tracer was selected with similar settling characteristics. Tracer was introduced to the seabed (water depth ≈30 m) and sediment samples taken on days 0, 3, 10, 17 and 30 to measure the horizontal and vertical distribution of tracer in sediments. A concentric sampling grid was established at radii of 25, 50, 100, 150, 200, 400, 700 and 1, 000 m from the source on transects 30° apart. The bulk of the deployed tracer was initially concentrated in an area 25 m radius from the release point; tracer was observed to steadily decrease to zero over a period of 30 days. In a 200 m region measured from the release point in the direction of the residual current, the redeposition of tracer was low. A Lagrangian particle tracking model was validated using these observed data by varying resuspension model parameters within limits to obtain the best agreement between spatial and temporal distributions. The validated model generally gave good predictions of total mass budgets (±7% of total tracer released), particulary where tracer concentrations were high near the release point. Best fit model parameters (critical erosion shear stress=0.018 N m−2, erodibility constan=60 g m−2 d−1) are at the low end of reported parameters for coastal resuspension models. Such a low critical erosion shear stress indicates that the frequency of resuspension and deposition events for freshly deposited material is high. 相似文献
30.
To prevent harm to human health from degrading ecosystems, epidemiologists need useful indicators that are sensitive to those
shifts in health status that might parallel these declines. Traditional measures of health (e.g., life expectancy, infant
mortality) are intuitively linkable to effects from environmental degradation but, in fact, they do not appear to provide
early warning indications of negative ecological impacts on health. Alternative health measures, such as social well-being,
may be needed for epidemiological research. New measures must combine those factors having policy relevance, including sensitive
measures of well-being and of health, with models of those human behaviours that contribute to ecological declines. Exposure
factors (e.g., pollution) made worse by ecosystem changes (e.g., global warming) also are relevant. In addition, epidemiologists
must be able to relate health outcomes not only to the traditional base of geo-political boundaries (e.g., census tracts or
countries), but more appropriately to eco-regions (e.g., climate regions). Only then could direct comparisons of effect be
made between areas that have eco-region as the common base for defining both denominators and numerator events for rate calculations
and comparisons. In conclusion, administrative infrastructure is needed so that meaningful eco-epidemiology can be conducted.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献