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31.
Abstract Major ions and stable isotopes in groundwaters of the Plio-Quaternary shallow aquifer of the Djerid oases, southern Tunisia, were investigated to elucidate the origin of groundwater recharge and the mineralization processes. It has been demonstrated that the groundwater composition is mainly controlled by the water–rock interaction, the encroachment of brines from the Chotts and the return flow of irrigation waters. The isotopically depleted groundwater samples suggest that the recharge waters derive from an old palaeoclimatic origin. However, the enriched groundwater samples reflect the presence of evaporated recharge water. Furthermore, the large negative deuterium-excess values indicate the effect of secondary evaporation processes, probably related to the return flow of irrigation waters pumped from the underlying aquifer. Editor D. Koutsoyiannis; Associate editor E. Custodio Citation Tarki, M., Dassi, L. and Jedoui, Y., 2012. Groundwater composition and recharge origin in the shallow aquifer of the Djerid oases, southern Tunisia: implications of return flow. Hydrological Sciences Journal, 57 (4), 790–804. 相似文献
32.
The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and the deterioration of water quality. The large amount of water shown to exchange tidally between the lagoon and the open sea suggests that while water per se is important and observed eutrophication problems are not caused by a lack of water. Heavy metal concentrations in surface sediments of the lagoon indicate that the ecosystem degradation is most likely related to the discharge of untreated phosphogypsum. Excessive pumping from the local freshwater aquifer that previously supplied freshwater to the lagoon via sub-aquatique fractures is likely to be a significant factor contributing to the water and sediment quality degradation of Boughrara Lagoon. 相似文献
33.
A new and high efficient scheme is developed for the Eulerian–Lagrangian Localized Adjoint Method (ELLAM) to solve the Advection–Dispersion transport Equation (ADE) on unstructured triangular meshes. To obtain accurate results, the new method requires a very limited number of integration points (usually 1 per element). 相似文献
34.
Three-Dimensional Modeling of Mass Transfer in Porous Media Using the Mixed Hybrid Finite Elements and the Random-Walk Methods 总被引：2，自引：0，他引：2
A three-dimensional (3D) mass transport numerical model is presented. The code is based on a particle tracking technique: the random-walk method, which is based on the analogy between the advection–dispersion equation and the Fokker–Planck equation. The velocity field is calculated by the mixed hybrid finite element formulation of the flow equation. A new efficient method is developed to handle the dissimilarity between Fokker–Planck equation and advection–dispersion equation to avoid accumulation of particles in low dispersive regions. A comparison made on a layered aquifer example between this method and other algorithms commonly used, shows the efficiency of the new method. The code is validated by a simulation of a 3D tracer transport experiment performed on a laboratory model. It represents a heterogeneous aquifer of about 6-m length, 1-m width, and 1-m depth. The porous medium is made of three different sorts of sand. Sodium chloride is used as a tracer. Comparisons between simulated and measured values, with and without the presented method, also proves the accuracy of the new algorithm. 相似文献
35.
Tunisian Chott’s region is one of the most productive artesian basins in Tunisia. It is located in the southwestern part of
the country, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the
water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow
pattern and time of residence. The system is composed of an upper unconfined “Plio-Quaternary” aquifer with a varying thickness
of 20–200 m, an intermediate confined/unconfined “Complex Terminal” aquifer about 100 m in thickness and a deeper “Continental
Intercalaire” aquifer about 150 m in thickness separated by thick clay and marl layers. The dissolution of evaporites and
carbonates explains part of the contained Na+, Ca2+, Mg2+, K+, SO42− and Cl-, but other processes, such carbonate precipitation, also contributes to the water composition. The stable isotope composition
of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient
water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the Plio-Quaternary
aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. 相似文献
36.
The lithology of the studied aquifers has an important effect on their hydrogeologic setting. Moreover, the structural patterns have their imprint on the geologic setting and consequently the hydrogeologic conditions of the area. Lake Nasser recharges the groundwater in the study area by large amount of water increasing the groundwater level. A comparison of the depth to water in the same wells at two different periods (1998 and 2014 ) shows that the depth to water increases with average rise 11.1 m during 16 years. The constructed water table map shows that the groundwater flow is mainly towards the northwest direction reflecting recharge from Lake Nasser. The hydraulic parameters of the Abu Aggag and Sabaya sandstone aquifers are determined in the present work from pumping tests. The transmissivity of the studied aquifers reflects the moderate to high potentiality. The groundwater salinity of the studied aquifers is fresh water and varies from 353 to 983 ppm (part per million) and suitable for all purposes. It increases due to the west direction coinciding with groundwater flow direction. The main result of the present study shows that the seepage water from Lake Nasser attains 17 mcm/year. 相似文献
37.
Geochemistry and petrography of REE-bearing Fe-oxide assemblages in Choghart iron deposit,Yazd, Iran
Younes Shekarian Ardeshir Hezarkhani Nima Najafi Anaraki Arash Nikvar Hassani 《Arabian Journal of Geosciences》2017,10(12):273
The Choghart magnetite-apatite deposit situated in the Bafq district, Central Iran, has been scrutinized for rare earth elements (REEs) by precise geochemical investigation. The Central Iran is a susceptible area of rare earth elements. One of the Choghart’s prominent points is the existence of hydrothermal zones which made prediction of REEs occurrence within the deposit possible. Choghart is placed within felsic volcanic tuffs, rhyolitic rocks, and volcanic sedimentary sections belonging to the lower Cambrian. Abundance and distribution pattern of REEs in Choghart iron deposits reveal a part of deposit formation and its mineralogical modifications. Petrography and mineralogy of the ore body demonstrated two main types of alterations (sodic and calcic) associated with iron ore mineralization in Choghart deposit. The main ore includes a large quantity of massive magnetite in the lower part of Choghart deposit. The minor mineralization involves apatite, pyrite, alkaline amphibole, especially actinolite and tremolite, calcite, talc, quart, monazite, and bastnasite. Geochemical sampling from north–northeast (N-NE) side of the mine denotes the presence of these elements in hydrothermal zones. Statistical populations of the area were categorized by fractal geometry into four main differentiations: host rock type (albitofyre), iron, metasomatose, phosphate zones, and a subset of the phosphate zone which is named high iron high phosphate type. REEs like lanthanum, neodymium, yttrium, and niobium constitute the most quantity of Choghart. Deposit characteristics demonstrate its similarity to Kiruna type. The significant feature of iron oxide-apatite deposits of Kiruna ore type is the existence of monazite inclusions within apatite. These inclusions were also observed within apatite type I and II of Choghart mineralization. Moreover, REEs geochemistry in Choghart deposit was identified by investigation on geochemical data analyses. The analysis represents negative Eu anomaly and further enrichment of light REEs compared to the heavy ones. Chondrite normalized REEs patterns are defined by negative anomalies of Eu, which is the main characteristic of Kiruna ore type. The results showed that REEs concentration in phosphate zone, as a high absorption of REEs, is much higher than metsomatose, albitofyre, and iron zones. REEs distribution in N-NE side of the mine indicated that the contact of iron ore with tailings in N-NW side of the mine leads REEs to be enriched nearly 1% , as well as that of NE with high contents of REEs 1.5% ), which is very significant. 相似文献
38.
Due to the non-linear coupling between flow and transport equations the simulation of real density driven flow problems requires a lot of computational time and/or heavy equipments. We suggest some approximations and numerical recipes to reduce the CPU costs for these strongly non-linear coupled equations without loss in accuracy. 相似文献
39.
This paper studies the interaction of linear water waves with a moored floating breakwater with a leeward boundary composed from a vertical wall. This describes a real modelling for the case of ports in contrary to the problems of unbounded domains. It involves the application of a partial reflection boundary condition for this sidewall. In fact, the partial reflection problem in practical application is of great importance in the design of a harbour or breakwater and mainly for short waves. The reflection coefficient of the harbour boundary (sidewall) plays an important role in modifying the performance of the floating breakwater. Moreover, it reduces the resonant peaks appearing inside the ports due to the energy accumulation in an enclosed domain. The effects of the variation of structural parameters of the breakwater on the transmitted wave height are discussed in details for various values of partial reflection. 相似文献
40.
Saad Younes Ghoubachi 《Arabian Journal of Geosciences》2011,5(5):1103-1115
The present work deals with the groundwater aquifer of the Lower Cretaceous sandstone and its sustainable development in Sinai. The studied aquifer system is the most promising groundwater system in Sinai due to its wide extension, hug storage, and good quality. The objective of this paper aims to elucidate the hydrogeological characteristics of the Lower Cretaceous aquifer. The aquifer system occurs under confined conditions. The top surface of the Lower Cretaceous dips steeply towards the southwest direction with step faults. The average sand percent of the penetrated aquifer attains 54%. The main direction of groundwater flow is generally from southwest and locally is concentric to the center of study area related to the influence of the graben block. The aquifer has a hydraulic gradient generally reaches 0.0011 m/m and attains 0.0028 in central portion of study area. The aquifer parameters (effective porosity, transmissivity, and hydraulic conductivity) increase towards the northeast direction with increasing of the sand percentage. Durov diagram plot revealed that the groundwater has been a final stage evolution represented by a NaCl water type. The groundwater salinity increases towards the central of study area coinciding with groundwater flow. The groundwater salinity of the Lower Cretaceous aquifer is brackish water and varies from 2,510 to 5,256 ppm and unsuitable for drinking and domestic purposes. 相似文献