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981.
Sigismond A. Wilson 《GeoJournal》2011,76(3):191-212
Although the Kimberley Process Certificate Scheme has considerably reduced the flow of conflict diamonds from 4% to less than
1%, other forms of illicit diamonds are estimated at 20% of global production. While scholars and policy makers have given
considerable attention to illicit mining and smuggling (with some success), illicit exploitation still hinders revenue generation
that is needed for economic growth and development in Sub-Saharan African (SSA) countries heavily reliant on alluvial minerals.
Based on surveys of 240 households in four diamondiferous chiefdoms in Kono District in Sierra Leone, key informant interviews,
focus groups and secondary data, and drawing from the actor-oriented approach and Le Billon (Fuelling war: natural resources
and armed conflict. London, International Institute for Strategic Studies, 2005) conceptualization of the political geography of the resource, this paper examines the problem of illicit diamond exploitation
in post-conflict Sierra Leone. It investigates: (1) the causes of illicit diamond mining and smuggling; (2) the spatial and
temporal aspects of illicit mining and smuggling, and (3) possible solutions to illicit diamond exploitation. The paper argues
that the ineffectiveness of national mining laws/policies has created conditions that are exploited by local and international
actors in the diamond industry. This is further exacerbated by the political geography of the resource. Study findings reveal
that while better mining regulation could reduce illicit exploitation, bringing buyers closers to miners and offering them
better prices for rough diamonds will minimize smuggling and thus increase government’s mineral revenue base. 相似文献
982.
The hydroxyl stretching frequencies of four phyllosilicates have been measured at high pressures and temperatures using an externally heated diamond-anvil cell and synchrotron infrared spectroscopy. Spectra were measured up to 26, 31, 21 and 8 GPa at room temperature for samples of talc, pyrophyllite, muscovite and 10-Å phase, respectively. Spectra were also measured in the range 273–500 K at ambient pressure for all samples and at 8–9 GPa for talc and pyrophyllite. The frequency of the Mg3OH band in talc increases with pressure due to the absence of hydrogen bonding. The different orientation of the hydroxyl group in pyrophyllite and muscovite leads to hydrogen bonding and a decrease in the frequency of the Al2OH band with pressure. 10-Å phase is approximately equivalent to talc with the addition of interlayer H2O. In a spectrum of a sample synthesised for 143 h, two hydroxyl stretching bands are clearly resolved on compression. One is the same as the Mg3OH band in talc, indicating the presence of intra-layer hydroxyl in a talc-like environment with no hydrogen bonding. The other, which separates from the talc-like band at 1 GPa, is associated with intra-layer hydroxyl that is hydrogen bonded to interlayer H2O. There are equivalent bands in high-pressure spectra of a sample of deuterated 10-Å phase, synthesised for 400 h. This sample shows a greater extent of hydrogen bonding at ambient pressure than the 143 h sample. For all of the phases studied, increasing temperature leads to a decrease in frequency for every hydroxyl stretching vibration, both at low and high pressures. The shifts in frequency with temperature are an order of magnitude greater than the shifts with pressure when normalised to previously measured structural parameters. 相似文献
983.
Impact of Berm Breaching on Hyperbenthic Macroinvertebrate Communities in Intermittently Closed Estuaries 总被引:1,自引:0,他引:1
Adrian W. T. Lill Gerard P. Closs Marc Schallenberg Candida Savage 《Estuaries and Coasts》2012,35(1):155-168
Berm breaching of intermittently closed estuaries, either naturally or due to management practices, results in a physicochemical
disturbance due to the flushing of water, material and biota into the ocean and the subsequent tidal influx. In 2007 and 2008
comparative and controlled studies were employed in three New Zealand estuaries: Sawmill Creek (46°04′ S 170°12′ E), Otokia
Creek (45°57′ S 179°20′ E) and Kaikorai Lagoon (45°56′ S 170°23′ E), to investigate the impact of berm breaching on the hyperbenthic
macroinvertebrate community in intermittently closed estuaries. Significant changes in community structure occurred in both
the weekly comparative and the controlled studies (ANOSIM P < 0.01). Furthermore, the catch per unit effort of both total
and key invertebrate taxa significantly increased after breaching (ANOVA P < 0.01). However, substantial numbers of individuals were expelled into the ocean (5,800 individuals, 20-min sample) while
new taxa immigrated into the estuaries. Along with migration-related changes to community structure, berm breaches also resulted
in the loss of ∼80% of inundated habitat and the concentration of existing populations. Consequently, the management of intermittent
estuary connections to the ocean has implications for the ecology of individual, managed estuaries and also for regional coastal
populations of epibenthic invertebrates. 相似文献
984.
The morphosedimentary evolution of a sector of the southern Espinhaco range (northern Minas Gerais State, Brazil) and its
regional neotectonic setting are presented herein. The studied site is a stream at base level flowing along the western border
of the range. Its identification was accomplished by using remote sensing techniques including the analysis of 3D slope models
generated with shuttle radar topography mission images. The main geomorphological features of the identified site were surveyed
in a 1:500 scale. In addition, seven stratigraphic logs are described. A regional geologic compilation and facies diagrams
were used as a basis for the integration of the geomorphological and stratigraphic data, which produced some conclusions about
the recent tectonic reactivations at the eastern border of Sao Francisco Craton. The results point to a local eastward tilting
of the Espinhaco range. This fact is in accordance with previous findings in neighboring areas and results in the asymmetric
evolution of the fluvial valley, as well as the regional relief. 相似文献
985.
This study assesses the origin and pollution of trace metals in surface soils in a region with contrasting land uses (urban
vs. rural). Principal component analysis (PCA) reveals that Cr and Ni are predominantly of geogenic origin. These two trace
metals are also the only ones with statistically significant correlations with soil particle size and organic matter content.
Copper, Pb and Zn, and possibly Hg, are of anthropogenic origin, but their concentrations rarely reach levels described as
strongly polluted by pollution indexes. The concentrations of these anthropogenic trace metals are statistically not different
in urban and rural areas, except for Pb that is higher in the urban area. This general lack of a difference between the two
land uses indicates that the influence of this small urban area on trace metal concentrations in soils is minor. Lead and
Zn have the most, but still a modest number, of strongly polluted sites, mainly in an industrial part of the city. GIS analysis
shows that, based on the pollution load index (PLI), overall concentrations of trace metals also reach their highest levels
in that industrial area. These observations indicate that the influence of industry on trace metal pollution in soil exceeds
that of other urban activities in the region. Local background concentrations were found to be very different from general
crustal background concentrations. This demonstrates the importance of the careful selection of a background type in studies
like this. 相似文献
986.
Soumyajit Mukherjee Hemin A. Koyi Christopher J. Talbot 《International Journal of Earth Sciences》2012,101(1):253-272
The Higher Himalayan Shear Zone (HHSZ) contains a ductile top-to-N/NE shear zone—the South Tibetan detachment system-lower
(STDSL) and an out-of-sequence thrust (OOST) as well as a top-to-N/NE normal shear at its northern boundary and ubiquitously distributed
compressional top-to-S/SW shear throughout the shear zone. The OOST that was active between 22 Ma and the Holocene, varies
in thickness from 50 m to 6 km and in throw from 1.4 to 20 km. Channel flow analogue models of this structural geology were
performed in this work. A Newtonian viscous polymer (PDMS) was pushed through a horizontal channel leading to an inclined
channel with parallel and upward-diverging boundaries analogous to the HHSZ and allowed to extrude to the free surface. A
top-to-N/NE shear zone equivalent to the STDSU developed spontaneously. This also indirectly connotes an independent flow confined to the southern part of the HHSZ gave
rise to the STDSL. The PDMS originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel.
The lower boundary of this faster PDMS defined the OOST. The model OOST originated at the corner and reached the vent at positions
similar to the natural prototype some time after the channel flow began. The genesis of the OOST seems to be unrelated to
any rheologic contrast or climatic effects. Profound variations in the flow parameters along the HHSZ and the extrusive force
probably resulted in variations in the timing, location, thickness and slip parameters of the OOST. Variation in pressure
gradient within the model horizontal channel, however, could not be matched with the natural prototype. Channel flow alone
presumably did not result in southward propagation of deformation in the Himalaya. 相似文献
987.
The vegetation damage assessment of the Wenchuan earthquake of May 2008 using remote sensing and GIS 总被引:1,自引:2,他引:1
The methodology for assessing the vegetation damaged by the Wenchuan earthquake by using the technologies of remote sensing
and GIS was discussed in Dujiangyan city of Sichuan Province, China. The model of extracting vegetation from CBERS images
was formulated using the differentiation knowledge of vegetation and non-vegetation discovered by image analysis and geographic
analysis. The damage degree index (DDI) of the vegetation was defined here, which was the difference of the normalized difference
vegetation index before the earthquake and that after earthquake. The China-Brazil Earth Resource Satellite (CBERS)-02’s images
acquired, respectively, on 6 May and 27 June 2008, the model of extracting vegetation, and DDI were used to obtain the information
about the area and degree of the damage vegetation in the study. There was 87.94 square kilometers vegetation damaged by Wenchuan
earthquake, which accounted for 7.9% of the total area in Dujiangyan city. The area percentage of the damage vegetation in
each grade related strongly and positively to the elevation grade and slope grade and weakly related to the aspect type. The
distribution characteristics of the damage vegetation were useful for making plan of restoring vegetation here. 相似文献
988.
Michael R. Williams Gopal Bhatt Solange Filoso Guido Yactayo 《Estuaries and Coasts》2017,40(5):1227-1246
In large part driven by total maximum daily load (TMDL) mandates, the restoration community in the Chesapeake Bay region has been implementing novel best management practices (BMPs) and stream restoration designs in urban areas, such as regenerative stream/stormwater conveyance (RSC) structures and stream-wetland complexes (SWCs). However, the nutrient and sediment reduction efficiencies of these novel designs are virtually unknown, and the possibility of increasing riverine flow in the Chesapeake Bay watershed associated with climate change this century necessitates an evaluation of their performance to develop and utilize those that optimize reductions in nutrient and sediment fluxes. We compare pre- and post-construction loads (total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS)) from RSCs (i.e., upland BMPs) and a SWC (i.e., stream restoration) constructed at the outflow of a highly developed watershed in the Coastal Plain physiographic province of Maryland. The largest of the two RSCs performed best in relation to expected nutrient and sediment reductions because of superior water retention capability. By the length of river reach restored, the SWC attained from 79 to 88% of its N reduction TMDL goal, but only 19 to 23 and 2.7 to 3.1% for TP and TSS, respectively; by watershed area, % attainments of TMDL goals were much lower. Results indicate that SWCs have the potential to curtail N loading from developed catchments, but additional water quality benefits may be limited. Climate change projections indicate that there will be an increased frequency of larger-volume storms that will result in an increase in stormflow runoff from urban areas, and increased pollutant loads will likely curtail potential gains made by efforts to achieve TMDL goals. Given the large-scale implementation of BMPs currently underway to accommodate the Chesapeake Bay TMDL, the restoration community needs to adopt a concerted strategy of building climate resilience into many types of urban BMPs to help attain and maintain loads at TMDL levels in anticipation of a progressively wetter climate throughout this century. 相似文献
989.
Yajun Xin Mengyuan Li Dingchao An Hongying Ji Jichun Kang 《Arabian Journal of Geosciences》2017,10(14):311
Based on calculations of rock fracture surface and angle, incremental-load creep experiments were conducted on two groups of major-defect fractured rock specimens in an RLW-2000 rheology test system. The research investigated the fracture type and the creep properties of major-defect fractured rock and analyzed the relationships between failure load and horizontal or vertical projection distance, and between each of theme and fracture area or angle. The results showed that rock fracture was divided into three types according to the distribution, including I, II, and III types. I, II, and III types were respectively an internal fracture running through neither the upper nor lower end, one through the upper or lower end and one through both upper and lower ends, and a III type was further sub-divided into IIII and IIIII types. The instantaneous strain was larger than the creep strain under the same creep loading stage. As the creep loading increased on two groups of major-defect fractured rock, the instantaneous strain decreased abruptly and then increased abruptly, while the creep strain decreased rapidly at first and later increased near-linearly. When the failure angle was larger than the friction angle, failure load was positively correlated with failure angle yet was negatively correlated with vertical projection distance. Vertical projection distance and fracture angle, which decided fracture type, controlled rock failure load. Failure load increased in turn from I type to III type, and low-type fracture determined mainly failure load in multiply-fracture specimen. 相似文献
990.
The current research has been conducted to evaluate groundwater aquifers qualitatively in the area located in the Western side of Qena city. The Quaternary aquifer represents the main groundwater source in the study area. It exists under unconfined to semiconfined conditions at depths varying between 4 m due North and 80 m in the South. The chemical analyses of the groundwater samples indicate that 77% of the total samples are fresh and 20% are brackish, while only 3% are saline. In addition, the iso-salinity contour map indicates that the salinity increases towards the central and northern parts of the study area. The total and permanent hardness increase as water salinity increases and vice versa in case of temporary hardness in the groundwater samples. The chemical water types and the ion ratios indicate meteoric origin of groundwater as well as the dissolution of terrestrial and marine salts. The contribution of recent recharge from the River Nile to a few groundwater wells in the study area varies from low to high. In addition, the most recharge sources are from the precipitation. Nitrate concentrations in groundwater increase towards the central and Northern areas significantly elevated in response to increasing anthropogenic land uses. Much of the solutes and physicochemical parameters in these waters are under the undesirable limits of World Health Organization (WHO) for drinking purpose, and a plot of sodium adsorption ratio versus EC shows that about 23% of the groundwater samples are good water quality, about 45% of groundwater samples are moderate quality, and 23% of the groundwater samples are intermediate water class, while the rest of samples (9%) are out of the range. 相似文献