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排序方式: 共有211条查询结果,搜索用时 15 毫秒
1.
S. Ramesh K. Nvv Murthy S. M. Hussain S. Ramasamy G. A. Ramadass 《Marine Georesources & Geotechnology》2020,38(1):57-63
AbstractPalar basin is located between Pennar and Cauvery sedimentary basins of East coast of India in Bay of Bengal, northeast Indian Ocean. Sea floor drill (Wire-line Autonomous Coring System – WACS) with operational capability of up to 3000?m water depth was developed to collect long cores from deep sea floor for geotechnical and ocean resource assessment studies. During the drilling operation it encountered Nummulitic coralline limestone of Lower Eocene age at 18 meters below the seafloor (mbsf) at 850?m water depth indicating carbonated platform presence for the first time at the study region. Bathymetry contour from Naval Hydrography Chart and General Bathymetric Chart of the Oceans (GEBCO) has revealed the presence of shallow mounds from 50 to 200?m depth closure contour near the sampling site at 850?m water depth which might be a submerged carbonated structure. Since, Nummulites are shallow water dwelling fauna (<20?m depth) but its occurrence at 18 mbsf in 850?m water depth is recorded because of the advancement in technology tool for long core sampling by means of sea floor drill. 相似文献
2.
Present environment and historic changes from the record of lake sediments, Dhaka City, Bangladesh 总被引:1,自引:0,他引:1
Changes in the urban environment of Dhaka City have been evaluated from the geochemical compositions of bottom sediments from two lakes, Gulshan-1 and –2. Abundances of Pb, Zn, Fe2O3 and total sulfur in a Gulshan-1 core gradually increase toward the sediment–water interface. Three stages of condition change can be recognized in Gulshan-1, based on trace metal concentration patterns. The basal Stage I corresponds to background Dhaka sedimentation, whereas gradual increase in Stage II represents the beginning of pollution. Marked increases in Pb and Zn in Stage III reflect rapid urban development and increased emissions to the atmosphere. The condition of the Dhaka environment is compared to that of Japan based on Zn–Fe2O3 and Pb–Fe2O3 relations. Zn–Fe2O3 ratios in Stage I Dhaka sediments are similar to normal Japanese sediments, whereas Stage II data lie on the same trend as Japan urban sediments. Dhaka Stage III samples have greater Zn:Fe2O3 ratios than Japanese urban sediments, suggesting Zn pollution from poorly-controlled industrial sources. In contrast, the Dhaka Pb–Fe2O3 trend lies between normal and urban Japanese sediments. Although vehicle emissions in Dhaka are now significant, the data suggest that Pb pollution from this source remains in its early stages. 相似文献
3.
S. Mahmood A. Ahmed A. Hussain M. Athar 《International Journal of Environmental Science and Technology》2005,2(3):193-199
Variability among populations was analyzed in five provenances of Acacia nilotica from spatially variable habitats. Populations of A. nilotica developed in response to their habitat conditions. The level of variability was significantly high among the populations. Phenotypic variability was extremely high for leaf and stipular spine characteristics. The nature of morphological variability for vegetative traits appeared environmentally controlled. The differentiation of leaf and stipular spine expression seems to have an adaptive significance for the species in terms of water economy. Although, seed and pod characteristics are genetically controlled showing a lower proportion of variability but these traits supported r and k-selection that may allow the species to survive under a wide array of contrasting habitats. The study suggested that populations of A. nilotica are differentiated in relation to the heterogeneity of environment. These populations became adapted to their habitat through the variability of morphological expressions. The morphologically differentiated populations of the species had allowed them to maintain themselves in a wide array of environmental situations enabling A. nilotica to occupy ample ecological ranges. 相似文献
4.
Sajjad Hussain Saima Gul Sabir Khan Habib ur Rehman 《Arabian Journal of Geosciences》2013,6(11):4547-4556
In the present study, the retention capacity of carbonaceous material obtained from the diesel engine exhaust mufflers for Cr(VI) removal has been investigated. The physicochemical properties such as density, pH of aqueous slurry, pH at point of zero charge, ash content, moisture content, volatile matter, surface area, scanning electron microscopy and electron dispersive spectroscopy of the carbonaceous material were determined. The capacity of adsorbent for removal of Cr(VI) from aqueous solution was observed under different experimental condition like contact time, initial concentration of metal ions, pH and temperatures on the adsorption capacity of the adsorbent. Maximum adsorption of Cr(VI) ions was found at low pH. The adsorption process was found to follow second-order kinetics. The rate constant was evaluated at different temperatures along with other thermodynamic parameters like activation energy, Gibbs free energy change, enthalpy change and entropy change. Both Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium of carbonaceous material at different temperatures. Langmuir isotherm shows better fit than Freundlich isotherm at given conditions. The result shows that low-cost carbonaceous material from diesel engine exhaust mufflers can be efficiently used for wastewater treatment containing Cr(VI) ions. 相似文献
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Sattam Almadani Elkhedr Ibrahim Mahfooz Hafez Hussain Alfaifi Talal Alharbi Kamal Abdelrahman Essam Abdel-Motaal 《Arabian Journal of Geosciences》2018,11(2):33
In the present study, the existence of cavities, voids, and fractures was verified at the site of the El-Elb Dam, which is located to the northwest of Riyadh City across Wadi Hanifa, using 2D electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) techniques. For this purpose, four ERT profiles were measured on the downstream side of the El-Elb Dam using the Syscal Pro Switch-72 resistivity meter. In addition, a GPR survey using a 400-MHz antenna and a SIR-3000 instrument was conducted along five profiles above the stilling basins on the downstream side of the dam and one radar profile was measured outside the stilling basins area across the course of the wadi. The resultant geophysical data were interpreted with the aid of information from a field-based structural and stratigraphic evaluation of the outcropped bedrock on the banks of the wadi course. The analysis of the inverted ERT and filtered radar sections revealed several resistivity and electromagnetic reflection anomalies that are identified laterally and vertically across the measured sections. These anomalies indicate the presence of fractures and karst features affected the limestone bedrock in the dam site. These near-surface karstified and fractured strata represent a critical hazard to the structural safety of the dam. 相似文献
8.
Natural Resources Research - Coal waste is a potential source of rare-earth elements (REEs) and some economically critical elements recovery. The present study reports the abundance and enrichment... 相似文献
9.
Journal of Oceanology and Limnology - Kuwait’s shrimp fishery presents typical tropical shrimp fishery characteristics with highly variable recruitment, fast growth and strong seasonal... 相似文献
10.
The chemical composition of the Dharwar metavolcanic suite from Chitaldrug is found to be similar to that of early Precambrian metabasalts from Canadian and Australian Shields. Its low K2O content and the similarities in the ferromagnesium trace elements with those of oceanic olivine normative tholeiites indicate a low K2O oceanic type of original magma. It is suggested that a protocontinent having a thin crust approaching basic composition existed during the pre-Dharwar era. 相似文献