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排序方式: 共有420条查询结果,搜索用时 31 毫秒
411.
Chia-Chuan Liu Jyoti Prakash Maity Jiin-Shuh Jean A. H. M. Selim Reza Zhaohui Li Bibhash Nath Ming-Kuo Lee Kao-Hung Lin Prosun Bhattacharya 《Environmental Earth Sciences》2012,66(5):1513-1523
Fluid and mud samples were collected from Wushanting (WST), Hsiaokunshui (HKS), Yenshuikeng (YSK), Kuantzeling (KZL), and
Kunshuiping (KSP) mud volcanoes of southwestern Taiwan. Concentrations of major ions and trace elements in mud volcanic fluids
were analyzed to find the possible linkage to elevated arsenic (As) concentrations in the Chianan plain groundwater. The elevated
Na+, K+, and Cl− concentrations indicated possible marine origin of the fluids. The trace element concentrations in the mud volcanic fluids
were generally low, but the As concentrations were up to 0.12 mg/L. High contents of As, Fe, and Mn were observed in the mud
samples. Saturation index calculations indicated that both carbonate and oxide minerals acted as potential sinks for As in
the mud volcanic fluids. Arsenic in the dewatering fluids and muds may be transported by the subsurface flow and surface streams
as suspended solids and eventually deposited in the Chianan plain aquifers. Under reducing conditions, As may be released
from the host minerals (such as Fe- and Mn-oxides/hydroxides), thereby causing widespread groundwater As pollution. 相似文献
412.
Kamlesh Verma Sanjeeb Bhattacharya A. M. Asim Ansari Prakash K. Srivastava Amit Dharwadkar 《Journal of the Geological Society of India》2014,83(5):532-534
Eleven glacial sediment samples collected from different elevation of Jutulsessen Nunatak, Gjelsvikfjella of East Antarctica were studied for the clay mineralogical analysis using X-ray diffraction technique. The result shows prominent peak at 10, and 3.34 Å suggesting the presence of biotite possibly derived from the catchment where biotite rich granite gneisses are exposed. The detailed investigation on the shape of biotite peak of certain samples shows the signs of alteration of biotite in to a mixed layer containing tri-octahedral smectite (low charge vermiculite). The presence of mixed layer along with the biotite is found to be associated with the samples of lower geomorphic level. The progressive alteration of clay sized biotite to form a mixed layer in the lower horizons of Jutulsessen Nunatak is probably due to the periodic accumulation of melt-water during the austral summer. 相似文献
413.
Kurt R. Petvipusit Ahmed H. Elsheikh Tara C. Laforce Peter R. King Martin J. Blunt 《Computational Geosciences》2014,18(5):763-778
Geologic CO2 sequestration in deep saline aquifers is a promising technique to mitigate the effect of greenhouse gas emissions. Designing optimal CO2 injection strategy becomes a challenging problem in the presence of geological uncertainty. We propose a surrogate assisted optimisation technique for robust optimisation of CO2 injection strategies. The surrogate is built using Adaptive Sparse Grid Interpolation (ASGI) to accelerate the optimisation of CO2 injection rates. The surrogate model is adaptively built with different numbers of evaluation points (simulation runs) in different dimensions to allow automatic refinement in the dimension where added resolution is needed. This technique is referred to as dimensional adaptivity and provides a good balance between the accuracy of the surrogate model and the number of simulation runs to save computational costs. For a robust design, we propose a utility function which comprises the statistical moment of the objective function. Numerical testing of the proposed approach applied to benchmark functions and reservoir models shows the efficiency of the method for the robust optimisation of CO2 injection strategies under geological uncertainty. 相似文献
414.
415.
Bhupendra K. Mishra Chandra S. Dubey Dericks P. Shukla Prosun Bhattacharya Arnold L. Usham 《Environmental Earth Sciences》2014,72(9):3281-3291
High Arsenic (As) concentrations have been reported in superficial water in the Yamuna flood plains (YFP), Delhi, which is being extensively used for agriculture. The concentration of As in some common vegetables such as Solanum lycopersicum (tomato), Abelmoschus esculentus (lady’s finger), Solanum melongena (brinjal), Lagenaria siceraria (bottle gourd), Raphanus sativus (radish), Zea mays (corn), and Luffa acutangula (ridge gourd) has been studied in this work. The range of As concentrations (dry weight) varies from 0.6 to 2.52 mg/kg with the highest accumulation of 2.52 mg/kg in radish followed by tomato (2.36 mg/kg). The order of As concentration in the decreasing order is R. sativus > S. lycopersicum > Z. mays > L. acutangula > L. siceraria > S. melongena > A. esculentus. Thus, As accumulation is the highest in roots and the lowest in least juicy fruits. The daily dietary intake of As through the consumption of various vegetables was also calculated. Though the mean As concentration was the highest in radish (2.52 mg/kg) but the highest amount of As is being consumed through tomato (0.383 mg/day), which is nearly three times the World Health Organization’s provisional maximum tolerable daily intake limit of 0.126 mg/day for a 60 kg person. High concentration of As in vegetables grown in YFP, Delhi is being reported here. This high contamination is primarily due to the presence of As in irrigation water having its source from coal-based thermal power plants in the vicinity of the area. If not checked properly, it will pose a serious health risk to people living in these densely populated areas surrounding YFP. 相似文献
416.
Paul Jacob Hancock Paul Roberts Michael J. Kesteven Ronald D. Ekers Elaine M. Sadler Tara Murphy Marcella Massardi Roberto Ricci Mark Calabretta Gianfranco de Zotti Philip G. Edwards Jennifer A. Ekers Carole A. Jackson Mark Leach Chris Phillips Robert J. Sault Lister Staveley-Smith Ravi Subrahmanyan Mark A. Walker Warwick E. Wilson 《Experimental Astronomy》2011,32(2):147-177
The Australia Telescope 20 GHz (AT20G) survey is a large area (2?? sr), sensitive (40 mJy), high frequency (20 GHz) survey of the southern sky. The survey was conducted in two parts: an initial fast scanning survey, and a series of more accurate follow-up observations. The follow-up survey catalog has been presented by Murphy et al. (MNRAS 402:2403, 2010). In this paper we discuss the hardware setup and scanning survey strategy as well as the production of the scanning survey catalog. 相似文献
417.
The ultimate bearing capacity of a number of multiple strip footings, identically spaced and equally loaded to failure at the same time, is computed by using the lower bound limit analysis in combination with finite elements. The efficiency factor (ξγ), due to the component of soil unit weight, is computed with respect to changes in the clear spacing (S) between the footings. It is noted that the failure load for a footing in the group becomes always greater than that of a single isolated footing. The values of ξγ for the smooth footings are found to be always lower than the rough footings. The values of ξγ are found to increase continuously with a decrease in the spacing between footings. As compared to the available theoretical and experimental results reported in literature, the present analysis provides generally a little lower values of ξγ. 相似文献
418.
In this study, an attempt has been made to estimate land surface temperatures (LST) and spectral emissivities over a hard
rock terrain using multi-sensor satellite data. The study area, of about 6000 km2, is a part of Singhbhum-Orissa craton situated in the eastern part of India. TIR data from ASTER, MODIS and Landsat ETM+
have been used in the present study. Telatemp Model AG-42D Portable Infrared Thermometer was used for ground measurements
to validate the results derived from satellite (MODIS/ASTER) data. LSTs derived using Landsat ETM+ data of two different dates
have been compared with the satellite data (ASTER and MODIS) of those two dates. Various techniques, viz., temperature and
emissivity separation (TES) algorithm, gray body adjustment approach in TES algorithm, Split-Window algorithms and Single
Channel algorithm along with NDVI based emissivity approach have been used. LSTs derived from bands 31 and 32 of MODIS data
using Split-Window algorithms with higher viewing angle (50°) (LST1 and LST2) are found to have closer agreement with ground
temperature measurements (ground LST) over waterbody, Dalma forest and Simlipal forest, than that derived from ASTER data
(TES with AST 13). However, over agriculture land, there is some uncertainty and difference between the measured and the estimated
LSTs for both validation dates for all the derived LSTs. LST obtained using Single Channel algorithm with NDVI based emissivity
method in channel 13 of ASTER data has yielded closer agreement with ground measurements recorded over vegetation and mixed
lands of low spectral contrast. LST results obtained with TIR band 6 of Landsat ETM+ using Single Channel algorithm show close
agreement over Dalma forest, Simlipal forest and waterbody with LSTs obtained using MODIS and ASTER data for a different date.
Comparison of LSTs shows good agreement with ground measurements in thermally homogeneous area. However, results in agriculture
area with less homogeneity show difference of LST up to 2°C. The results of the present study indicate that continuous monitoring
of LST and emissivity can be undertaken with the aid of multi-sensor satellite data over a thermally homogeneous region. 相似文献
419.
The southwestern margin of the Eastern Ghats Belt characteristically exposes mafic dykes intruding massif-type charnockites.
Dykes of olivine basalt of alkaline composition have characteristic trace element signatures comparable with Ocean Island
Basalt (OIB). Most importantly strong positive Nb anomaly and low values of Zr/Nb ratio are consistent with OIB source of
the mafic dykes. K-Ar isotopic data indicate two cooling ages at 740 and 530 Ma. The Pan-African thermal event could be related
to reactivation of major shear zones and represented by leuco-granite vein along minor shear bands. And 740 Ma cooling age
may indicate the low grade metamorphic imprints, noted in some of the dykes. Although no intrusion age could be determined
from the present dataset, it could be constrained by some age data of the host charnockite gneiss and Alkaline rocks of the
adjacent Prakasam Province. Assuming an intrusion age of ∼1.3Ga, Sr-Nd isotopic composition of the dykes indicate that they
preserved time-integrated LREE enrichment. In view of the chemical signatures of OIB source, the mafic dykes could as well
be related to continental rifting, around 1.3Ga, which may have been initiated by intra-plate volcanism. 相似文献
420.
Manish Kumar Pankaj Kumar A.L. Ramanathan Prosun Bhattacharya Roger Thunvik Umesh K. Singh M. Tsujimura Ondra Sracek 《Journal of Geochemical Exploration》2010
Groundwater with high geogenic arsenic (As) is extensively present in the Holocene alluvial aquifers of Ghazipur District in the middle Gangetic Plain, India. A shift in the climatic conditions, weathering of carbonate and silicate minerals, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon (6.4–259.5 μg/L) when compared to the post-monsoon period (5.1–205.5 µg/L). The As enrichment was encountered in the sampling sites that were close to the Ganges River (i.e. south and southeast part of Ghazipur district). The depth profile of As revealed that low concentrations of NO3− are associated with high concentration of As and that As depleted with increasing depth. The poor relationship between As and Fe indicates the As release into the groundwater, depends on several processes such as mineral weathering, O2 consumption, and NO3− reduction and is de-coupled from Fe cycling. Correlation matrix and factor analysis were used to identify various factors influencing the gradual As enrichment in the middle Gangetic Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. Saturation in both periods is reached for crystalline Fe phases such as goethite, but not with respect to poorly crystalline Fe phases and any As-bearing phase. The results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO2 is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The present study is vital considering the fact that groundwater is an exclusive source of drinking water in the region which not only makes situation alarming but also calls for the immediate attention. 相似文献