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Un site aquifère contaminé, situé en bordure de l’oued Meboudja (Annaba, Algérie), a été caractérisé en mettant en place une surveillance de la qualité des eaux de surface et souterraines affectées par les nombreux rejets industriels et urbains sur une période de 11 ans (1999?2009). Les déchets industriels sont déposés directement sur le sol et les effluents sont déversés dans l’oued Meboudja sans aucun traitement préalable. Les eaux souterraines présentent une conductivité électrique élevée (de 1000 à 6000 μS/cm), de fortes teneurs en chlorure et en sodium avec respectivement un maximum de 1400 et 730 mg/L. Partant des résultats de l’analyse en composantes principales effectuée sur 33 puits en juillet 2009, les trois principaux processus responsables de l’évolution chimique observée au niveau de l’aquifère ont été identifiés: (a) l’apport salifère du lac Fetzara et le lessivage des formations métamorphiques carbonatées (responsables de l’augmentation de la minéralisation) ; (b) l’alimentation de la nappe par les eaux de l’oued Meboudja, recevant de nombreux polluants industriels (responsable des fortes teneurs en fer et en manganèse) ; et (c) l’utilisation des produits chimiques dans l’agriculture (responsable de l’augmentation des teneurs en nitrates). Les fortes minéralisations sont enregistrées notamment dans les puits situés à proximité des rejets industriels. En outre, de fortes concentrations métalliques en fer et en manganèse sont observées dans les eaux de l’oued. L’évolution de ces deux éléments dans les eaux de la nappe au cours d’un cycle hydrologique montre que l’augmentation des teneurs est liée notamment à une réalimentation de la nappe par l’oued et à une mauvaise oxygénation de la nappe. L’existence de niveaux argileux peut en effet jouer le rôle d’écran en surface et favoriser les conditions réductrices dans la nappe. La Meboudja agit par conséquent comme une source diffuse de contaminants tout au long de son parcours. Les caractéristiques hydrodynamiques de l’aquifère ont été estimées à l’aide de l’interprétation des données des pompages d’essai effectués dans plus d’une dizaine de puits. Des modèles d’écoulement et de transport de polluants ont été élaborés en utilisant le code MODFLOW-MT3D. L’ampleur de la migration des contaminants a été évaluée pendant une période de 11 ans (1999?2009). L’interaction oued-nappe est considérée comme responsable de la migration des contaminants dans la plaine de la Meboudja.
EDITEUR Z. W. KundzewiczEDITEUR ASSOCIÉ C. Leduc 相似文献
43.
Non‐linear stochastic inversion of gravity data via quantum‐behaved particle swarm optimisation: application to Eurasia–Arabia collision zone (Zagros,Iran) 
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下载免费PDF全文 Potential field data such as geoid and gravity anomalies are globally available and offer valuable information about the Earth's lithosphere especially in areas where seismic data coverage is sparse. For instance, non‐linear inversion of Bouguer anomalies could be used to estimate the crustal structures including variations of the crustal density and of the depth of the crust–mantle boundary, that is, Moho. However, due to non‐linearity of this inverse problem, classical inversion methods would fail whenever there is no reliable initial model. Swarm intelligence algorithms, such as particle swarm optimisation, are a promising alternative to classical inversion methods because the quality of their solutions does not depend on the initial model; they do not use the derivatives of the objective function, hence allowing the use of L1 norm; and finally, they are global search methods, meaning, the problem could be non‐convex. In this paper, quantum‐behaved particle swarm, a probabilistic swarm intelligence‐like algorithm, is used to solve the non‐linear gravity inverse problem. The method is first successfully tested on a realistic synthetic crustal model with a linear vertical density gradient and lateral density and depth variations at the base of crust in the presence of white Gaussian noise. Then, it is applied to the EIGEN 6c4, a combined global gravity model, to estimate the depth to the base of the crust and the mean density contrast between the crust and the upper‐mantle lithosphere in the Eurasia–Arabia continental collision zone along a 400 km profile crossing the Zagros Mountains (Iran). The results agree well with previously published works including both seismic and potential field studies. 相似文献
44.
Inland notches: lithological characteristics and climatic implications of subaerial cavernous landforms in Israel 下载免费PDF全文
下载免费PDF全文 Inland notches, are elongated concave‐shape indentations that develop on the carbonate rocky cliffs of mountainous zones, down to the desert fringe. These rock shelters form as a result of the interaction between specific petrologic characteristics and climatic controls, emphasizing the importance of environment upon rock decay. Inland notches are shaped due to slight differences (1–15%) in the porosity of the visor and cavity bed: the cavity bed is more porous, so more likely to erode by exfoliation and dissolution. Thus, the cavity bed retreats at a faster rate compared to the slower subaerial dissolution of the visor bed, until a critical point is reached where the visor collapses. In Israel, inland notches inhabit the same lithostratigraphic units as do large caves. The vast majority (71%) of inland notches are formed in hard, dense, and crystalline limestone deposited throughout the Turonian age. Another 27% are cut into the dolomitic sequence of the upper Albian and lower Cenomanian. The rest (2%) are dispersed in the various formations of the Cenomanian and Eocene eras. Notches are most common in semi‐arid and in Mediterranean climates but mainly in areas with annual rainfall of between 400 mm and 850 mm. In more humid areas (> 900 mm/yr) notches are negligible or completely absent, due to the rapid rate of chemical dissolution of carbonate rocks. In the desert fringe (200–300 mm/yr), mechanical decay is accelerated and notches exhibit disintegration processes, visor collapse, and rock falls. In the desert area (< 200 mm/yr), salt decay replaces the chemical decay characteristic of inland notches, encouraging tafoni formation. In addition, notches form through fluvial activity or on account of greater petrophysical differences between consecutive beds; i.e. elongated cavities may form in soft rocks, shaded by harder visors or crusts. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
45.
Using of neural networks for the prediction of nitrate groundwater contamination in rural and agricultural areas 总被引：1，自引：0，他引：1
Khamis Al-Mahallawi Jacky Mania Azzedine Hani Isam Shahrour 《Environmental Earth Sciences》2012,65(3):917-928
As a neural network provides a non-linear function mapping of a set of input variables into the corresponding network output,
without the requirement of having to specify the actual mathematical form of the relation between the input and output variables,
it has the versatility for modeling a wide range of complex non-linear phenomena. In this study, groundwater contamination
by nitrate, the ANNs are applied as a new type of model to estimate the nitrate contamination of the Gaza Strip aquifer. A
set of six explanatory variables for 139 sampled wells was used and that have a significant influence were identified by using
ANN model. The Multilayer Perceptrons (MLP), Radial Basis Function (RBF), Generalized Regression Neural Network (GRNN), and Linear Networks were used. The best network found to simulate Nitrate
was MLP with six input nodes and four hidden nodes. The input variables are: nitrogen load, housing density in 500-m radius
area surrounding wells, well depth, screen length, well discharge, and infiltration rate. The best network found had good
performance (regression ratio 0.2158, correlation 0.9773, and error 8.4322). Bivariate statistical test also were used and
resulting in considerable unexplained variation in nitrate concentration. Based on ANN model, groundwater contamination by
nitrate depends not on any single factor but on the combination of them. 相似文献
46.
The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray spectrometric data has been utilized to identify geological factors controlling uranium mobility in the geological units along the three detailed study locations of Kab Al-Abyad, South Wadi (W) Al-Tarafawy and W. Al-Farkhah; their eTh/eU ratios averaging around 4.1, 3.7 and 5.6 respectively. Quantitative analysis with the integration of mobility maps and geological studies suggest two systems controlling U-migration within the geological units (confined system and unconfined system). In the confined system, the syngenetically formed U have experienced mobility after leaching and are redistributed in the presence of an incorporation carrier during transportation (probably as carbonate complexes). Then the retardant for uranium is achieved by sorption or by coprecipitation with the aid of Fe oxy-hydroxide, and finally the formation of immobile secondary U-bearing minerals takes place along a lithogeochemical trap. In contrast to the confined system, the unconfined one is basically lacking the lithogeochemical trap which in?uences the final accumulation of U-bearing minerals. The radioactivity of the trachyte rocks arises from the radioactive minerals uranophane and beta-uranophane with U- and/or Th-bearing minerals samarskite, Th-rich REE silicates, monazite and allanite. 相似文献
47.
Ahmed AbdelRazek Rami M El-Sherbiny Hani A Lotfi 《Geomechanics and Geoengineering》2018,13(4):288-300
The use of granulated recycled rubber as a lightweight material in civil engineering applications has been widely growing over the past 20 years. Processed waste tires mixed with soils have been introduced as lightweight fills for slopes, retaining walls, and embankments. It has also been considered as a damping material under foundations in seismic zones. Understanding the properties of sand-rubber mixtures is essential to evaluate its performance in geotechnical applications. Isotopically consolidated drained (CD) triaxial tests were conducted to investigate the effect of rubber size, content and saturation condition on the mechanical properties of sand-rubber mixtures. Moreover, the compressibility of the sand-rubber mixtures under sustained loading was investigated through one dimensional consolidation tests. The unit weight, shear strength and stiffness of sand-rubber mixtures decreased whereas deformability increased at increased rubber content. A non-linear stress-strain response was observed, that changed from brittle to ductile behaviour at increased rubber content. Sand-rubber mixtures, under one dimensional loading, exhibited significant settlement that increased as rubber content increased. 相似文献
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Vibration mitigation using smart, reliable and cost‐effective mechanisms that requires small activation power is the primary objective of this paper. A semi‐active controller‐based neural network for base‐isolation structure equipped with a magnetorheological (MR) damper is presented and evaluated. An inverse neural network model (INV‐MR) is constructed to replicate the inverse dynamics of the MR damper. Next, linear quadratic Gaussian (LQG) controller is designed to produce the optimal control force. Thereafter, the LQG controller and the INV‐MR models are linked to control the structure. The coupled LQG and INV‐MR system was used to train a semi‐active neuro‐controller, designated as SA‐NC, which produces the necessary control voltage that actuates the MR damper. To evaluate the proposed method, the SA‐NC is compared to passive lead–rubber bearing isolation systems (LRBs). Results revealed that the SA‐NC was quite effective in seismic response reduction for wide range of motions from moderate to severe seismic events compared to the passive systems. In addition, the semi‐active MR damper enjoys many desirable features, such as its inherent stability, practicality and small power requirements. The effectiveness of the SA‐NC is illustrated and verified using simulated response of a six‐degree‐of‐freedom model of a base‐isolated building excited by several historical earthquake records. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Elias SALAMEH Hani KHOURY W. Uwe REIMOLD Werner SCHNEIDER 《Meteoritics & planetary science》2008,43(10):1681-1690
Abstract— Triggered by re‐evaluation of a 1960s report on the regional geology of the northeastern border region of Jordan and following Landsat satellite image investigation, a 5.5 km diameter, complex, circular structure was discovered in the central eastern region of the Kingdom of Jordan. Initial ground truthing revealed complex geological structures involving Upper Cretaceous and Paleogene strata, and including a prominent outer rim rising up to 60 m above the surrounding plain, an intermediate ring of up to 20 m elevation within a ring syncline, and a central zone of stratigraphically uplifted sedimentary strata characterized by intense macroscopic (folding and faulting, widespread cataclasis) and locally mesoscopic (cataclasis) deformation. Ten sites with shatter cone development in fine‐grained sandstone or limestone have been mapped to date, mostly in the outer parts of the central uplifted area. This finding confirms that the Jebel Waqf as Suwwan structure was formed as the result of the impact of an extraterrestrial projectile. Search for impact‐diagnostic micro‐deformation has been rather unsuccessful: only 1 quartz grain with both planar deformation features and planar fractures has been detected in a sandstone sample to date. The overall majority of the approximately 70 samples investigated by micropetrographic analysis consist of extremely fine‐grained chert, siltstone, or marly limestone. Cataclasis is widespread in chert and limestone, also on the micro‐scale. Considering the severely limited amount of characteristic impact microdeformation, and the stratigraphic situation within the central uplift, it is likely that a relatively deep level of the central uplift is currently exposed. The extensive drainage demonstrated for this region supports the conclusion that this impact structure could be quite deeply eroded‐especially as its geology involves some relatively soft lithologies (marls, limestones). The age of this impact event is at present poorly constrained at post‐Middle to Lower Eocene. 相似文献
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Siwa oasis is located in the extreme western part of the Egyptian western desert. There are several archaeological sites in
the oasis; the most distinct ones are Alexander the Great temple at Aghormi hill and the Gebel El Mota tomb excavations. They
have suffered due to deterioration and cracks of different kinds and some parts are getting worse as rock falls occur. From
field inspection and lab analysis, it is clear that lithology plays an important role on the extent of damage. Alexander the
Great temple was built over the northern edge of Aghormi hill, which consists of two distinct beds—an upper limestone bed
and a lower shale one. From field survey and laboratory analysis, the shale is considered as a high expanded bed and weak
in its bearing capacity, as its clay content (mainly smectite) experienced swelling due to wetting from the ground water spring
underneath. Consequently, the upper limestone bed suffered from map cracking associated with rock falls due to the differential
settlement of the swelled lower shale one. The temple was threatened by slope instability and had experienced many cracks.
At Gabal El Mota tomb excavations, it was noticed that a comparison of tombs of the same opening size revealed that those
that excavated on shale beds had cracked much more than those that excavated on limestone. This may be attributed to the low
bearing capacity of excavated shale walls. The remedial measures suggested to overcome the stability problems on these archaeological
sites are grouting or construction of retaining walls. 相似文献