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181.
NILANJAN DASGUPTA TARITWAN PAL JOYDEEP SEN TAMOGHNO GHOSH 《Journal of Earth System Science》2011,120(4):617-626
The study involves the characterization of pegmatoidal granite, southeast of Beawar, Ajmer district, Rajasthan. Earlier researchers
had described this granite as part of the BGC, basement to the Bhim Group of the Delhi Super Group rocks. However, the present
study indicates that it is younger than the rocks of Bhim Group of South Delhi Fold Belt, into which it is intrusive. The
intrusion is structurally controlled and the outcrop pattern is phacolithic. The granite had intruded post-D2 deformation of the Delhi orogeny along the axial planes of D2 folds. The intrusion has also resulted in the formation of a contact aureole about the calc gneisses. 相似文献
182.
Catarina Vinagre João Salgado Henrique N. Cabral Maria J. Costa 《Estuaries and Coasts》2011,34(4):663-674
River flow variability is known to influence estuarine production, yet knowledge on its effect upon estuarine food webs dynamics
is still scarce. Stable carbon and nitrogen isotopes were used to assess the effect of river flow in the connectivity and
food web interactions between the two main fish nursery areas of the Tagus estuary. The aims of the present work were to investigate
the seasonal variation in food web structure and the exchange rate of individuals of marine juvenile fish among estuarine
nurseries, to compare the spring of a rainy year (2001) with that of an average year (2000), and to investigate the impact
of the winter floods of 2001. A low level of connectivity was observed for the fish species that use these areas as nurseries.
In low river flow conditions, two isotopically distinct food webs were established in each nursery area. These food webs were
very sensitive to small variations in the freshwater input. Winter floods seem to disrupt the localized food webs that are
established in low river flow periods, leading to the re-establishment of a wider food web. While in rainy years this wide
food web is maintained until spring, in average years the food web undergoes fragmentation into two localized and isotopically
distinctive food webs. The increase in frequency of droughts due to climate change should lower the connectivity of the estuarine
fish nurseries food webs, causing habitat fragmentation and consequent loss in complexity and resilience. 相似文献
183.
Sudip Dey Sushmita Paul Chandrani Debbarma Prasamita Sarkar 《Journal of the Geological Society of India》2011,77(4):367-376
The present work concentrates on microstructure imaging for visualising the changes of depositional environment during Tertiary
period. For that purpose Tipam layers of Gajalia fold area in southern Tripura was selected which was deposited during late
Tertiary period under marine-coastal environment. Thin sections of eleven selected samples of the study area were prepared
in the laboratory for microstructure analysis. For visualising the crystalline particles or quartz brightness and contrast
of the image was increased up to maximum level. Surface conditions of the samples were analysed within RGB combination. The
grain size and shapes of the eleven samples tested prove that the depositional environment remained very dynamic through Tertiary
period in the study area. The microstructure and surface conditions also strongly support this view. 相似文献
184.
Mobility of aqueous contaminants at abandoned mining sites: insights from case studies in Sardinia with implications for remediation 总被引:1,自引:0,他引:1
Rosa Cidu 《Environmental Earth Sciences》2011,64(2):503-512
Public awareness of environmental health issues has increased significantly in recent years, creating the need for detailed
scientific studies that can identify potential environmental problems. This paper reports the results of hydrogeochemical
surveys carried out in Sardinia, an Italian region with a long mining history. When mining operations in Sardinia ceased,
actions for limiting the potential adverse effects of mine closure on the water system were not undertaken. Drainages from
flooded mines and seeps from mining residues left on the ground are the main mining-related sources of contamination in Sardinia.
Due to the proximity of mining sites to water resources and land that is within reach of animals and humans, the major risks
to human health are associated with the direct discharge of contaminated waters into the streams and soils located down-gradient
of the abandoned mines. Results of hydrogeochemical surveys carried out under different seasonal conditions showed that the
dispersion of toxic and harmful elements (As, Cd, Ni, Pb, Sb and Zn) increases during the rainy season, especially under high
runoff conditions. These results should help regional and national authorities to address present environmental regulations,
particularly those regarding the quality of water resources. Furthermore, the results might be useful elsewhere for planning
remediation actions at abandoned mining sites. Lessons learned by past mining in Sardinia indicate that correct disposal and
management of mining residues should be mandatory from the beginning of exploitation and processing at each active mine. This
would allow reduction of the environmental risks as well as the cost of remediation. 相似文献
185.
In dam safety assessment, it is customary to focus on stability analysis, and the safety factor is regarded as an assessment
index that cannot correctly reflect the effect of multi-factors and variable uncertainty. The factors that induce dam breaks
are complex and uncertain; however, three primary ones can be identified: hydrological factors, seepage and bank slope instability.
In this paper, the risk probability and the dam break threshold value for each factor individually, as well as coupled factors,
are studied. The threshold value is acquired using the relationship formula between risk probability and dam type. The Dongwushi
reservoir located in the Hebei province of China is taken as a case study. The results show that the dam break threshold values
for hydrological factors, seepage and bank slope instability are 2.53, 2.02 and 2.69, respectively. The integrated dam break
threshold value for the coupled factors is 1.25, which indicates that the dam is under serious stress according to the established
risk assessment standard. The safety factor is calculated as 1.15 using the Bishop method, which indicates that the dam is
under serious stress. The results obtained by the proposed method are consistent with those of the Bishop method. Finally,
the proposed theory and method are introduced into a dam safety evaluation system (DSES) for convenient and efficient dam
safety management. 相似文献
186.
Mohamed E. Hereher 《Environmental Earth Sciences》2011,64(4):1117-1125
A set of six Landsat satellite images with 5–9 years apart was used in a post-classification analysis to map changes occurred
at Rosetta promontory between 1973 and 2008 due to coastal erosion. Spectral information were extracted from two multi-spectral
scanner (MSS) images (1973 and 1978), three thematic mapper (TM) images (1984, 1990, and 1999), and one enhanced thematic
mapper plus (ETM+) image (2008). To estimate the quantity of land loss in terms of coastal erosion, a supervised classification
scheme was applied to each image to highlight only two classes: seawater and land. The area of each class was then estimated
from the number of pixels pertaining to this class in every image. In addition, the shoreline position was digitized to address
retreat/advance pattern throughout the study period. Results showed that Rosetta promontory had lost 12.29 km2 of land between 1973 and 2008 and the shoreline withdrew southward about 3.5 km due to coastal erosion. Most land loss and
shoreline retreat occurred between 1973 and 1978 (0.55 km2/year and 132 m/year, respectively). Coastal protection structures were constructed successively at the promontory. These
structures have considerably contributed to reduce coastal erosion; however, they promoted downdrift erosion. 相似文献
187.
Sarah A. S. Dare Sarah-Jane Barnes Hazel M. Prichard Peter C. Fisher 《Mineralium Deposita》2011,46(4):381-407
Magmatic sulfide deposits consist of pyrrhotite, pentlandite, chalcopyrite (± pyrite), and platinum-group minerals (PGM).
Understanding the distribution of the chalcophile and platinum-group element (PGE) concentrations among the base metal sulfide
phases and PGM is important both for the petrogenetic models of the ores and for the efficient extraction of the PGE. Typically,
pyrrhotite and pentlandite host much of the PGE, except Pt which forms Pt minerals. Chalcopyrite does not host PGE and the
role of pyrite has not been closely investigated. The Ni–Cu–PGE ores from the South Range of Sudbury are unusual in that sulfarsenide
PGM, rather than pyrrhotite and pentlandite, are the main carrier of PGE, probably as the result of arsenic contribution to
the sulfide liquid by the As-bearing metasedimentary footwall rocks. In comparison, the North Range deposits of Sudbury, such
as the McCreedy East deposit, have As-poor granites in the footwall, and the ores commonly contain pyrite. Our results show
that in the pyrrhotite-rich ores of the McCreedy East deposit Os, Ir, Ru, Rh (IPGE), and Re are concentrated in pyrrhotite,
pentlandite, and surprisingly in pyrite. This indicates that sulfarsenides, which are not present in the ores, were not important
in concentrating PGE in the North Range of Sudbury. Palladium is present in pentlandite and, together with Pt, form PGM such
as (PtPd)(TeBi)2. Platinum is also found in pyrite. Two generations of pyrite are present. One pyrite is primary and locally exsolved from
monosulfide solid solution (MSS) in small amounts (<2 wt.%) together with pyrrhotite and pentlandite. This pyrite is unexpectedly
enriched in IPGE, As (± Pt) and the concentrations of these elements are oscillatory zoned. The other pyrite is secondary
and formed by alteration of the MSS cumulates by late magmatic/hydrothermal fluids. This pyrite is unzoned and has inherited
the low concentrations of IPGE and Re from the pyrrhotite and pentlandite that it has replaced. 相似文献
188.
Gonca Gencalioglu-Kuscu 《International Journal of Earth Sciences》2011,100(8):1967-1985
Central Anatolian Volcanic Province (CAVP) is a fine example of Neogene-Quaternary post-collisional volcanism in the Alpine-Mediterranean
region. Volcanism in the Alpine-Mediterranean region comprises tholeiitic, transitional, calc-alkaline, and shoshonitic types
with an “orogenic” fingerprint. Following the orogenic volcanism, subordinate, within-plate alkali basalts (sl) showing little or no orogenic signature are generally reported in the region. CAVP is mainly characterized by widespread
calc-alkaline andesitic-dacitic volcanism with orogenic trace element signature, reflecting enrichment of their source regions
by subduction-related fluids. Cora Maar (CM) located within the Erciyes pull-apart basin, is an example to numerous Quaternary
monogenetic volcanoes of the CAVP, generally considered to be alkaline. Major and trace element geochemical and geochronological
data for the CM are presented in comparison with other CAVP monogenetic volcanoes. CM scoria is basaltic andesitic, transitional-calc-alkaline
in nature, and characterized by negative Nb–Ta, Ba, P and Ti anomalies in mantle-normalized patterns. Unlike the “alkaline”
basalts of the Mediterranean region, other late-stage basalts from the CAVP monogenetic volcanoes are classified as tholeiitic,
transitional and mildly alkaline. They display the same negative anomalies and incompatible element ratios as CM samples.
In this respect, CM is comparable to other CAVP monogenetic basalts (sl), but different from the Meditterranean intraplate alkali basalts. Several lines of evidence suggest derivation of CM and
other CAVP monogenetic basalts from shallow depths within the lithospheric mantle, that is from a garnet-free source. In a
wider regional context, CAVP basalts (sl) are comparable to Apuseni (Romania) and Big Pine (Western Great Basin, USA) volcanics, except the former have depleted Ba
contents. This is a common feature for the CAVP volcanics and might be related to crustal contamination or source characteristics.
Indeed, HFS and other incompatible element ratios suggest the role of crustal contamination in the genesis of the CAVP monogenetic
basalts. 相似文献
189.
David L. Naftz Frank J. Millero Blair F. Jones W. Reed Green 《Aquatic Geochemistry》2011,17(6):809-820
Great Salt Lake (GSL) is one of the largest and most saline lakes in the world. In order to accurately model limnological
processes in GSL, hydrodynamic calculations require the precise estimation of water density (ρ) under a variety of environmental conditions. An equation of state was developed with water samples collected from GSL to
estimate density as a function of salinity and water temperature. The ρ of water samples from the south arm of GSL was measured as a function of temperature ranging from 278 to 323 degrees Kelvin
(oK) and conductivity salinities ranging from 23 to 182 g L−1 using an Anton Paar density meter. These results have been used to develop the following equation of state for GSL (σ = ± 0.32 kg m−3):
r- r0 = 184.0 10 6 2 + 1.0 4 70 8*\textS - 1. 2 10 6 1*\textT + 3. 1 4 7 2 1 \textE - 4*\textS 2 + 0.00 1 9 9 \textT 2 - 0.00 1 1 2*\textS*\textT, \rho - \rho^{0} = { 184}.0 10 6 2 { } + { 1}.0 4 70 8*{\text{S}} - 1. 2 10 6 1*{\text{T }} + { 3}. 1 4 7 2 1 {\text{E}} - 4*{\text{S}}^{ 2} + \, 0.00 1 9 9 {\text{T}}^{ 2} - 0.00 1 1 2*{\text{S}}*{\text{T}}, 相似文献
190.
K PEDIADITI F BUONO F POMPIGNA C BOGLIOTTI E NURLU G LADISA G P PETROPOULOS 《Journal of Earth System Science》2011,120(5):949-961
Despite common acknowledgement of the value of protected areas as instruments in ensuring sustainability, and their promotion
for the achievement of policies on halting the loss of biodiversity, there is no common approach today for monitoring and
evaluating them. This paper presents a novel integrated nature conservation management procedure developed to monitor and
evaluate the sustainability of Mediterranean protected areas. This procedure was successfully implemented and formally evaluated
by protected area managers in six Mediterranean countries, results of which are presented here together with an overview of
the web-based Decision Support System (DSS) developed to facilitate its wide adoption. The DSS and procedure has been designed
and evaluated by managers as a useful tool, which facilitates and provides needed procedural guidance for protected area monitoring
whilst minimizing input requirements to do so. The procedure and DSS were developed following a review of existing protected
area assessment tools and a detailed primary investigation of the needs and capacity of its intended users. Essentially, the
procedure and DSS guides provide the facilities for protected area managers, in following a participatory approach to develop
a context-specific sustainability monitoring strategy, for their protected area. Consequently, the procedure is, by design,
participatory, context specific, holistic and relevant to protected area management and institutional procedures. The procedure
was piloted and formally evaluated in Greece, Italy, Turkey, Egypt, Malta and Cyprus. Feedback collected from the pilot evaluations
is also summarised herein. 相似文献
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