排序方式： 共有69条查询结果，搜索用时 26 毫秒
41.
High fluoride groundwater occurs in Maku area, in the north of West Azarbaijan province, northwest of Iran. Groundwater is
the main source of drinking water for the area residents. Groundwater samples were collected from 72 selected points including
40 basaltic and 32 nonbasaltic springs and wells, in two stages, during June and August 2006. The areas with high fluoride
concentrations have been identified, and the possible causes for its variation have been investigated. Regional hydrogeochemical
investigation indicates that water-rock interaction is probably the main reason for the high concentration of ions in groundwater.
The concentration of F− in groundwater is positively correlated with that of HCO3
− and Na+, indicating that groundwater with high HCO3
− and Na+ concentrations help to dissolve some fluoride-rich minerals. All of the water samples, collected from the basaltic areas
do not meet the water quality standards for fluoride concentration and some other parameters. Hence, it is not suitable for
consumption without any prior treatment. Inhabitants of the area that obtain their drinking water supplies from basaltic springs
and wells are suffering from dental fluorosis. The population of the study area is at a high risk due to excessive fluoride
intake especially when they are unaware of the amount of fluoride being ingested due to lack of awareness. 相似文献
42.
The Ilam Formation (Santonian–Campanian in age), part of the Bangestan Group, is disconformably overlain by the Sarvak Formation and underlain by the Gurpi Formation in the Tang-E Rashid, Peyon area, Izeh (Zagros), southwest of Iran.Facies analyses indicate that the Ilam carbonates formed in four microfacies belts: tidal flat, lagoon, shoal and open marine, in a platform ramp environment. Major and minor elements and carbon and oxygen isotope values were used to determine the original carbonate mineralogy of the Ilam Formation. Petrographic evidence and elemental and oxygen and carbon isotope values indicate that aragonite was the original carbonate mineralogy in the Ilam Formation. The elemental and isotopic compositions of the Ilam carbonates also illustrate that they have stabilized in the marine phreatic environment. Variations of Sr/Ca and δ18O values versus Mn suggest that diagenetic alteration occurred in a closed system. Temperature calculation based on the oxygen isotope value of the least-altered sample indicates that the very early shallow burial fluid temperature was around 28 °C.Recognition of the exact boundary between the Ilam and Sarvak Formations is difficult, due to similar lithologies and the absence of the Surgah Formation in the study area. However, elemental and oxygen and carbon isotope analysis were used to determine the boundary between these formations. The δ18O and δ13C values, along with elemental results, clearly indicate a subaerial exposure surface, below which meteoric diagenesis affected the sediments. 相似文献
43.
ABSTRACTIn this study, over 1000 data from the literature was used to characterize and compare the density, strengths, modulus, fracture toughness, porosity and the ultimate shear strengths of the gypsum, limestone and sandstone rocks. The compressive modulus and Mode-1 fracture toughness of the gypsum rock, limestone rock and sandstone rocks varied from 0.7 GPa to 70 GPa, and from 0.03 MPa.m0.5 to 2.6 MPa.m0.5 respectively. Vipulanandan correlation model was effective in relating the modulus of elasticity, fracture toughness with the relevant strengths of the rocks. A new nonlinear Vipulanandan failure criterion was developed to quantify the tensile strength, pure shear (cohesion) strength and to predict the maximum shear strength limit with applied normal stress on the gypsum, limestone and sandstone rocks. The Vipulanandan failure model predicts the maximum shear strength limit was, as the Mohr-Coulomb failure model does not have a limit on the maximum shear strength. With the Vipulanandan failure model based on the available data, the maximum shear strengths predicted for the gypsum, limestone and sandstone rocks were 64 MPa, 114 MPa and 410 MPa respectively. 相似文献
44.
Marie-Pierre Aubry William A. Berggren Christian Dupuis Holeil Ghaly David Ward Chris King Robert W. O'B. Knox Khaled Ouda Moustafa Youssef Wael Fathi Galal 《地学学报》2009,21(4):237-256
We present a review of archaeological and geological studies on the West Bank as a basis for discussing the geological setting of the tombs and geologically related problems with a view to providing archaeologists with a framework in which to conduct their investigations on the restoration, preservation and management of the antique monuments. Whereas the geology of the Upper Nile Valley appears to be deceptively simple, the lithological succession is vertically variable, and we have recognized and defined several new lithological units within the upper Esna Shale Formation. We have been able to delineate lithological (shale/limestone) contacts in several tombs and observed that the main chambers in some were excavated below the Esna Shale in the Tarawan Chalk Formation. We have been able to document changing dip in the strata (warping) in several tombs, and to delineate two major orientations of fractures in the field. Investigations behind the Temple of Hatshepsut, in the Valley of the Kings and around Deir El Medina have revealed four broad regional structures. We confirm that the hills located near the Nile Valley, such as Sheik Abdel Qurna, do not belong to the tabular structure of the Theban Mountain, but are discrete displaced blocks including the Thebes Limestone, as supported by Google Earth photographs. 相似文献
45.
Mohammadyousef Roghani Ph.D. Ying Li Ph.D. Nader Rezaei Ph.D. Ariel Robinson Elham Shirazi Ph.D. Kelly G. Pennell Ph.D. 《Ground Water Monitoring & Remediation》2021,41(2):112-121
Hazardous waste site investigations have shown that volatile organic compounds (VOCs) can be transported via sewer pipes and migrate into indoor spaces. Despite field data confirming the presence of this exposure pathway, there is lack of context-based numerical models that provide guidance to characterize and predict VOCs concentration in sewer gas at vapor intrusion sites. Particularly, this poses a challenge when assessing and mitigating risks associated with these exposure pathways. Therefore, a numerical model has been developed to simulate the concentration of VOCs in sewer gas in different stages throughout the sewer lines. The developed model considers various input parameters, including temperature, sewer liquid depth, groundwater depth, and sewer construction characteristics to incorporate local and operational conditions. The model's output is verified using field data from a sewer system constructed near a Superfund site. Moreover, a sensitivity analysis was conducted to evaluate the model's response to variation of the external input parameters. To the best of our knowledge, this study is the first attempt to model VOCs concentration in sewer gas, particularly to address vapor intrusion. The developed model can be used as a numerical tool to support the development of sewer assessment guidelines, risk assessment studies, and mitigation strategies. 相似文献
46.
Geotechnical Risk Assessment of Mine Development Intersections with Respect to Mining Sequence 总被引：2，自引：2，他引：0
Wael Abdellah Hani S. Mitri Denis Thibodeau Lindsay Moreau-Verlaan 《Geotechnical and Geological Engineering》2014,32(3):657-671
Mine developments such as haulage drifts and their intersections with cross-cuts are the only stope access in sub-level stoping mining system. Thus, they must remain stable during their service life. Haulage drift instability could lead to serious consequences such as: production delay, damage to equipment, loss of reserves and high operational cost. The goal of this paper is the stability of mine developments with respect to mining sequence with focus on the performance of haulage drift intersection during the production plan. A case study, the #1 Shear East orebody at Vale’s Garson Mine in Sudbury Ontario will be examined in this paper. A three-dimensional, elastoplastic, finite difference code (FLAC3D) is used for this study. The extent of strength-to-stress ratio corresponds to Mohr–Coulomb strength-to-stress ratio of 1.4 is used as failure evaluation criterion. The unsatisfactory performance is reached when the extent of strength-to-stress ratio exceeds the anchorage limit of the rockbolt. Stochastic analysis; adopting point-estimate method, is then employed with the numerical modelling to tackle the inherent uncertainty associated with rockmass properties. Then, the probability of instability at various mining steps is estimated for the roof and north wall of the studied intersection. The cost of consequence models is introduced to provide an economical solution if the intersection failed, blocked or damaged. Furthermore, the geotechnical risk associated with the instability of mine development intersection is estimated using risk-indexing tool. The results are presented and categorized in terms of probability, cost of consequence and risk-index at various mining stages. 相似文献
47.
Ahmed E. Khalil Hatem M. El-Desoky Taher M. Shahin Wael Abdelwahab 《Arabian Journal of Geosciences》2018,11(4):74
Wadi Hammuda is dominated by a variety of low grade regionally metamorphosed volcaniclastic metasediments pertaining to two different geotectonic settings and intruded by arc and late collision granitic rocks. Thus, the volcaniclastic metasediments which form extensive outcrops are considered as a member of island arc assemblages. This paper deals with the petrography, geochemistry, and tectonic setting of the island arc volcaniclastic metasediment rock units. The volcaniclastic metasediments consist of interbedded metagreywackes, metasiltstones, metamudstones, and schists as well as metapyroclastics. They are well foliated, crenulated and tightly folded, metamorphosed, and intruded by granitic rocks. Geochemical data support the petrographic classification and reveal that these volcaniclastic metasediments are generally low-K, essentially tholeiitic in character, with the exception of some metasediments and metapyroclastics which exhibits calc-alkaline and tholeiitic affinities and represent the first stage of island arc volcanism. The overthrusted oceanic lithosphere blocks with fragments of the fore arc and/or back-arc marginal basins volcaniclastic metasediments were incorporated among the island arc volcanics which supported by tectonically relationship between the different rock units in the study area. Contemporaneous with this deformation event, Wadi Hammuda was subjected to low grade regional metamorphism and the rocks document an early phase of shearing and/or foliation. Occasionally minor folds were developed particularly in the metasediments and schists. The subsequent emplacement of the syn-tectonic granites (tonalites and granodiorites) resulted in minor local thrusts. During the regional thrusting event which preceded the emplacement of the late-tectonic granites (alkali feldspar granites) and affected the whole region, low grade successions cover the study area similar to the Meatiq volcaniclastic metasediments. 相似文献
48.
49.
A comparative study of various commercially available programs in slope stability analysis 总被引：1，自引：0，他引：1
Wael Alkasawneh Abdallah I. Husein Malkawi Jamal Hassan Nusairat Nermeen Albataineh 《Computers and Geotechnics》2008,35(3):428-435
The objective of this paper is to study the effect of different slip surface search techniques on the factors of safety obtained using the limit equilibrium (LE) slope stability methods. This objective is accomplished by comparing results from the finite element method, the linear grid method, the rectangular grid method, and the Monte-Carlo searching techniques using different commercially available programs. The results showed that the LE methods are very efficient methods when coupled with a robust searching technique namely the Monte-Carlo method. In addition, the selected slip surface search technique highly influenced the location of the critical slip surfaces as well as the value of the calculated factors of safety. 相似文献
50.
SCOPED‐W: SCalable Online Platform for extracting Environmental Data and Water‐related model outputs 
下载免费PDF全文
下载免费PDF全文 Yaniss Guigoz Elham Rouholahnejad Nicolas Ray Grégory Giuliani 《Transactions in GIS》2017,21(4):748-763
This article presents SCOPED, an innovative approach for extracting environmental data using OGC services. In the field of water resource management, SCOPED‐W (‘W’ for ‘Water’) is a method that was developed in the framework of EU/FP7 IASON and EOPOWER projects. This platform supports the collection of data required to build a Soil and Water Assessment Tool (SWAT) model and the uptake, spatialization and dissemination of raw data generated from the outputs of different SWAT models for the Black Sea region. Scientists are documenting the data served by the platform in ISO standardized metadata to support informed use. SCOPED‐W primarily targets the community of SWAT users in the Black Sea region but it can easily be replicated in other geographical areas. Additionally, the SCOPED approach is based on data interoperability that makes it fully compatible with other domains of application as demonstrated here with three original use cases. The article also highlights the benefits of the approach for the GEO community and discusses future improvements for supporting integration with other platforms such as UNEP Live. 相似文献