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Natural Hazards - The sliding incidences along the mountainous roads in the northern part of Algeria are considered a major hazard, often with huge impacts on infrastructures, causing terrible... 相似文献
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Mohamed Metwaly Ahmed Ismail Jun Matsushima 《应用地球物理》2007,4(3):221-230
Ground penetrating radar （GPR） is one of the promising technologies that can be used to detect landmines. Many factors may affect the ability of GPR to detect landmines. Among those factors are： 1） the type of landmine material （metallic or plastic）, 2） conditions of the host soil （soil texture and soil moisture）, and 3） the radar frequency utilized. The impact of these factors on the ability of GPR to detect landmines is investigated by studying their effect on the dielectric permittivity contrast between the landmine and the host soil, as well as on the attenuation of the radar waves. The impact of each factor was theoretically reviewed and modeled using the Matlab and Mathcad software packages. Results of the computer modeling were correlated with GPR data acquired for metallic and plastic landmine types. It was found that the ability of GPR to detect landmines depends to a great extent on the landmine type, water content of the host soil, utilized radar frequency, and soil texture. The landmines are much easier to detect than plastic landmines for any soil conditions and any radar frequency. Increasing the soil＇s moisture content, regardless of soil texture, eases the detection of the plastic landmine and worsens the detection of the metallic mines. Increasing the percentage of clay in the soil causes the same effect as the moisture content. However, higher radar frequency delivers better results for landmine detection as long as the percentage of clay and the moisture content in the soil remains low. The results of this study are expected to help in selecting optimum radar antennae and data acquisition parameters depending on the landmine type and environmental conditions. 相似文献
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Integrated geoelectrical survey for groundwater and shallow subsurface evaluation: case study at Siliyin spring, El-Fayoum, Egypt 总被引：3，自引：1，他引：2
Mohamed Metwaly Gad El-Qady Usama Massoud Abeer El-Kenawy Jun Matsushima Nasser Al-Arifi 《International Journal of Earth Sciences》2010,99(6):1427-1436
Siliyin spring is one of the many natural fresh water springs in the Western Desert of Egypt. It is located at the central
part of El-Fayoum Delta, which is a potential place for urban developments and touristic activities. Integrated geoelectrical
survey was conducted to facilitate mapping the groundwater resources and the shallow subsurface structures in the area. Twenty-eight
transient electromagnetic (TEM) soundings, three vertical electrical soundings (VES) and three electrical resistivity tomography
(ERT) profiles were carried out around the Siliyin spring location. The dense cultivation, the rugged topography and the existence
of infra structure in the area hindered acquiring more data. The TEM data were inverted jointly with the VES and ERT, and
constrained by available geological information. Based on the inversion results, a set of geoelectrical cross-sections have
been constructed. The shallow sand to sandy clay layer that forms the shallow aquifer has been completely mapped underneath
and around the spring area. Flowing of water from the Siliyin spring is interconnected with the lateral lithological changes
from clay to sand soil. Exploration of the extension of Siliyin spring zone is recommended. The interpretation emphasizes
the importance of integrating the geoelectrical survey with the available geological information to obtain useful, cheap and
fast lithological and structural subsurface information. 相似文献
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Sixty-five sediment samples and 25 water samples were collected from Al-Mujib reservoir, central Jordan, in order to investigate
the heavy metal and ionic contamination assessment. Therefore, to achieve this aim, water and sediment samples were collected
during winter and summer seasons (2007) from Al-Mujib reservoir and the areas surrounding it. The study shows that there are
elevated levels of SO4
2−, Cl− and Na+ in reservoir water, which might originate from anthropogenic activities in the reservoir catchment area. In addition, the
reservoir water has higher total hardness (TH) values together with high Ca and Mg contents. This might be attributed to pH
of reservoir water and the nature of the rocks exposed in the catchment area. The average levels of heavy metals in reservoir
sediments are Fe = 14,888.1, Cu = 17.8, Zn = 88.6, Ni = 38.7, Cd = 4.4, Mn = 337.9 and Pb = 6.1 mg/kg, which are lower than
that observed in Wadi Al-Arab reservoir, northern Jordan. The values of enrichment factor are Cd = 35.5, Ni = 3.02, Zn = 2.54,
Cu = 1.26, Mn = 1.2 and Pb = 0.57; these values indicate that heavy metals in sediments of Al-Mujeb reservoir have a different
anthropogenic incrimination inputs. The study showed that the sediments are polluted with Cd, relatively contaminated with
Ni and Zn and uncontaminated with respect to Mn, Pb and Cu. 相似文献
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Waleed K. Zubari 《Hydrogeology Journal》1999,7(2):197-208
Over-abstraction of the Dammam aquifer, the principal aquifer in Bahrain, by the agricultural and domestic sectors, has led
to its salinization by adjacent brackish and saline water bodies. A hydrochemical study identified the locations of the sources
of aquifer salinization and delineated their areas of influence. The investigation indicates that the aquifer water quality
is significantly modified as groundwater flows from the northwestern parts of Bahrain, where the aquifer receives its water
by lateral underflow from eastern Saudi Arabia, to the southern and southeastern parts. Four types of salinization of the
aquifer are identified: brackish-water up-flow from the underlying brackish-water zones in north-central, western, and eastern
regions; seawater intrusion in the eastern region; intrusion of sabkha water in the southwestern region; and irrigation return
flow in a local area in the western region. Four alternatives for the management of groundwater quality that are available
to the water authorities in Bahrain are discussed and their priority areas are proposed, based on the type and extent of each
salinization source, in addition to groundwater use in that area. The effectiveness of the proposed management options in
controlling the degradation of water quality in the Dammam aquifer should be evaluated using simulation modeling.
Received: June 1998 Revised: November 1998 Accepted: December 1998 相似文献
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We present a theoretical weakly nonlinear analysis of the dynamics of an inviscid flow submitted to both rotation and precession of an unbounded cylindrical container, by considering the coupling of two Kelvin (inertial) waves. The parametric centrifugal instability known for this system is shown to saturate when one expands the Navier–Stokes equation to higher order in the assumed small precession parameter (ratio of precession to rotation frequencies) with the derivation of two coupled Landau equations suitable to describe the dynamics of the modes. It is shown that an azimuthal mean flow with differential rotation is generated by this modes coupling. The time evolution of the associated dynamical system is studied. These theoretical results can be compared with water experiments and also to some numerical simulations where viscosity and finite length effects cannot be neglected. 相似文献
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Waleed M. M. Mahmoud Nareman D. H. Khaleel Ghada M. Hadad Randa A. Abdel‐Salam Annette Haiß Klaus Kümmerer 《洁净——土壤、空气、水》2013,41(9):907-916
Sulfonamides (SAs) are one of the most frequently used antibiotics. SAs have been found in various environmental compartments. If SAs are not degraded in the environment, they can affect bacteria by their antibiotic properties and contribute to bacterial antibiotic resistance. Therefore, the biodegradability of 11 SAs (sulfanilamide, sulfaguanidine monohydrate, sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethazine, sulfamethoxazole, and sulfadimethoxine) was studied. For this purpose, the Closed Bottle Test (CBT, OECD 301D) was performed, which includes a toxicity control. In order to monitor the environmental fate of the parent compound and to check for transformation products, a simple, efficient, and reliable HPLC–UV method for the simultaneous determination of these SAs has been developed. Acetonitrile and water (with 0.1% formic acid) were used as mobile phase solvents for gradient elution. The method was validated in terms of precision, detection and quantitation limits, selectivity, and analytical solution stability. In the CBT, none of these SAs was readily biodegradable. The HPLC–UV analysis confirmed that no degradation of any SA took place. In the toxicity control, these SAs showed no toxic effect in the used concentration of environmental bacteria applied in the test. 相似文献
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The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management.The presence of such features hinders the extension of urbanizations particularly in the new metropolitan.The eastern part of Saudi Arabia contains various types of karstic limestone,sinkholes,solution cavities and voids.In this context,geophysical methods particularly electrical resistivity technique is used as a cost-effective solution for investigating subsurface caves,voids,and shallow weathered zones.2-D electrical resistivity data sets have been acquired along seven profiles in the new urbanization at Al Hassa area.Data processing has been carried out taking into consideration the response of synthetic models,which simulates physical models of the most common karstic features in the area.The results are very useful to determine the extension of shallow weathered zones and to locate different cavities underneath them.The hard limestone bedrock can also be detected and traced along the surveyed profiles. 相似文献