A Review of Some Environmental Issues Affecting Marine Mining     

Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.  相似文献   

Applied social area analysis: Defining and evaluating areas for urban neighbourhood councils   总被引：1，自引：0，他引：1  

Derek R. Hall 《Geoforum》1977,8(5-6)

Urban neighbourhood councils, neither statutorily established nor widely initiated in England, are seen to possess a number of advantages over existing forms of representative participation in relation to the equitable distribution of resources. In Portsmouth a community area perception survey and principal components analysis of census data were undertaken to produce synthesised ‘best fit’ social sub-areas upon which to base neighbourhood councils. These areas were then analysed in terms of their relevance and appropriateness, terms specifically defined, along four scale dimensions. An original contention that for maximum effectiveness neighbourhood councils should be established to cover all urban residential areas was confounded by the manifest irrelevance of the neighbourhood council concept in certain socio-spatial contexts.  相似文献   

Commentary on duplicative publications     

Derek B. Booth 《Quaternary Research》2007,68(1):1

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Correlating specific conductivity with total hardness in limestone and dolomite karst waters     

Wies&#x;awa Ewa Krawczyk  Derek C. Ford 《地球表面变化过程与地形》2006,31(2):221-234

Under field conditions modern digital conductivity meters give standardized, rapid and reproducible measurements. Here we investigate the accuracy of their estimates of the composition of karst waters, as total hardness (TH, as mg/L CaCO₃) for limestone and dolomite. These are the fundamental measures of process in carbonate karst geomorphology. PHREEQC theoretical curves for the dissolution of pure calcite/aragonite and dolomite in water at 25 °C are compared with water analyses from karst studies worldwide. Other principal ions encountered are sulphates, nitrates and chlorides (the ‘SNC’ group). From carbonate karsts, 2309 spring, well and stream samples were divided into uncontaminated (SNC < 10%), moderately contaminated (10 < SNC < 20%), and contaminated (SNC > 20%) classes. Where specific conductivity (SpC) is less than 600 µS/cm, a clear statistical distinction can be drawn between waters having little contamination and substantially contaminated waters with SNC > 20%. As sometimes claimed in manufacturers' literature, in ‘clean’ limestone waters TH is close to ¹/2SpC, with a standard error of 2–3 mg/L. The slope of the best‐fit line for 1949 samples covering all SNC classes where SpC < 600 µS/cm is 1·86, very close to the 1·88 obtained for clean limestone waters; however, the value of the intercept is ten times higher. The regression line for clean limestone waters where SpC > 600 µS/cm helps to distinguish polluted waters from clean waters with possible endogenic sources of CO₂. In the range 250 < SpC < 600 µS/cm, dolomite waters can be readily distinguished from limestone waters. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Short-Timescale Chemo-Mechanical Effects and their Influence on the Transport Properties of Fractured Rock     

Derek Elsworth  Hideaki Yasuhara 《Pure and Applied Geophysics》2006,163(10):2051-2070

Anomalous changes in permeability are reported in fractures circulated by fluids undersaturated with respect to the mineral host. Under net dissolution and net removal of mineral mass, fractures may alternately gape or seal, depending on the prevailing mechanical and chemical conditions. The influence on transport properties is observed to be large, rapid, and irreversible: Permeabilities may change by two orders of magnitude in a month, and the direction of permeability change may switch spontaneously, for no apparent change in environmental forcing. These behaviors are apparent in continuous circulation experiments conducted on fractures in novaculite and limestone, intermittently imaged by X-ray CT. In novaculite, permeability reduces by two orders of magnitude as silica is net removed from the sample. Surprisingly, these changes can occur at modest temperatures (~80°C) and stresses (~3.5 MPa), where compaction progresses as temperatures are incremented. Isothermal (~20°C) circulation tests in limestone show similar compaction driven by pressure solution. Where circulation remains undersaturated in Ca, the change in permeability spontaneously switches from net reduction to net increase as a wormhole forms. The surprising magnitude and rapidity of these changes are investigated in the context of the competition between stress- and chemistry-mediated effects.  相似文献   

Carolina Thunder Revisited: Toward a Transcultural View of Winston Cup Racing*     

Derek H. Alderman  Preston W. Mitchell  Jeffrey T. Webb  Derek Hanak 《The Professional geographer》2003,55(2):238-249

Almost three decades ago, cultural geographer Richard Pillsbury documented the national expansion of NASCAR and what he considered the erosion of major‐league stock car racing as a unique southern tradition. This claim is reassessed in light of recent research, leading us to suggest that the sport is actually “transcultural” in nature. It is influenced simultaneously by tradition and transition, as well as regional and national forces. In revisiting Pillsbury's seminal work, we document major changes and continuities in Winston Cup racing and briefly examine two North Carolina cases that provide contradictory views on the current relationship between the sport and the American South. North Wilkesboro illustrates how the changing geography of track locations can devalue and demoralize places associated with the tradition of southern stock car racing. The greater Charlotte area demonstrates that the South remains an important part of NASCAR, serving as a gathering place and “knowledge community” for drivers, racing teams, and fans from across the country. In addition to advancing research in the geography of sport and popular culture, the article encourages readers to think critically about regional cultures and their relationship to the forces of nationalization.  相似文献   

Simulation Experiments with Cometary Analogous Material     

Kochan  Hermann W.  Huebner  Walter F.  Sears  Derek W. G. 《Earth, Moon, and Planets》1998,80(1-3):369-411

Comet simulation experiments are discussed, in the context of physical models and the results in cometary physics, gathered especially from the GIOTTO space mission to comet P'Halley. The “status of the today knowledge” about comets, the experiments could start from, is briefly reviewed. The setup of the KOSI (German = Kometen Simulation) - experiments and the techniques to produce cometary analogous material, on the basis of that knowledge are described in general, as for the different KOSI experiments. The limitations of the simulation of physical processes at the surface of real comets in an earth-bound laboratory are discussed, and the possibilities to receive common insights in cometary physics are shown. Methods and procedures are described, and the major results reviewed. As with attempting to reproduce any natural phenomenon in the laboratory, there are short-comings to these experiments, but there are possibly major new insights to be gained. Physical laws only have the same consequences under same experimental or environmental conditions. A number of small-scale comet simulation experiments have been performed, since the early 60ties in many laboratories, but the largest and most ambitious series of comet simulation experiments to date were performed between 1987 and 1993 using the German space agency's (DLR) space hardware testing facilities in Cologne. These experiments were triggered by the scientific community after the comet P'Halley's recurrence in 1986 and the many data gathered by the space missions in this year. Simulation experiments have proved valuable in developing methods for making cometary analogues, and for exploring specific properties of such materials in detail. These experiments provided new insights into the morphology and physical behavior of aggregates formed out of silicate- /water-ice -grains likely to exist in comets. The formation of a dust mantle on the surface, and a system of ice layers below the mantle from the different admixed materials, have been detected after the insolation of the artificial comet. The mechanisms for heat transfer between the comet's surface and its interior, compositional, structural, and isotopic changes that occur near the comet's surface, were described by modeling in accordance with the experimental results. The mechanisms of the ejection of dust and ice grains from the surface, and the importance of gas-drag in propelling grains were investigated by close-up video cameras. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Paul Barringer: The tribute continues     

Derek Sears 《Meteoritics & planetary science》1998,33(4):546-546

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The foreshore: geographical implications of the three legal systems in Great Britain     

Derek J McGlashan  Robert W Duck  Colin T Reid 《Area》2004,36(4):338-347

Despite the word 'foreshore' being in common usage relating to the coast, it has three distinct legal definitions in Great Britain. There are three property law regimes, English law in England and Wales, Scots law (feudal) in Scotland and Udal tenure in parts of Orkney and Shetland. These result in the boundaries between private property interests and public property interests lying in a different position on the beach area under each of these property regimes. This paper examines the physical extent of each of the foreshore definitions and highlights a number of associated issues that rely on these different boundaries fundamentally impacting upon the management of the coast.  相似文献   

The chemistry of star formation     

Derek Ward-Thompson  Helen Fraser  Jonathan Rawlings 《Astronomy& Geophysics》2002,43(4):4.26-4.27

Understanding the chemistry of molecular clouds is now realized to be fundamental to our understanding of the whole star-formation process. A two-day meeting was held within NAM2002 to bring together chemists and astronomers to discuss this complex subject. Derek Ward-Thompson, Helen Fraser and Jonathan Rawlings report.