Impact of anthropogenic activities on the groundwater resources of the unconfined aquifer of Triffa plain (Eastern Morocco)

Located at the northeastern part of Morocco, the plain of Triffa is characterized by a semi-arid climate where water resources are rather fragile and influenced by a highly irregular rainfall distribution, both in time (annual and inter-annual distribution) and in space. The mean annual rainfall does not exceed 240 mm. In the Triffa plain, the impact of anthropogenic activities on the groundwater resources is reflected both by (a) the decrease in the piezometric level due to the over exploitation and droughts and (b) the deterioration of the chemical quality of water. Currently, this situation is felt mainly by the farmers. The unconfined aquifer is under stress due to the increase of the pollution rate, especially by nitrates that are above the WHO standards, and salinity. Organochlorine pesticides are ubiquitous and persistent organic pollutants used widely in agriculture. Due to their extensive use in agriculture, organic environment contaminants such as hexachlorocyclohexane, DDT, and DDD along organochlorine pesticides are distributed globally by transport through water. Pesticides such as aldrin, lindane, and heptachlor have also been detected and were considered as indicators showing the need to inform and to train farmers on the pesticides and fertilizers use in order to reduce the threat of groundwater contamination.     

Microwave enhancement in coronal holes: Statistical properties

We report on the statistical properties of the microwave enhancement (brightness temperature, area, fine structure, life time and magnetic field strength) in coronal holes observed over a period of several solar rotations.     

Rupture line and damage effects in Aqaba area, Egypt

Strong-motion parameters, peak ground acceleration, peak ground velocity, and peak ground displacement depend on several factors, such as the source of earthquake, distance between the source and site, and the characteristics of that site. Five seismographs and two accelographs were installed by the Egyptian Geological Survey team along the western side of the Gulf of Aqaba from Taba to Sharm El-Sheikh to record seismic events during the period from September 1995 to June 1996. During this period, two events were recorded by the accelographs. The two accelographs were located on the surface of the basement rocks, the first near the epicenter and the second at a farther distance. However, the farthest accelograph recorded higher values compared to the nearer one. Fault mechanics are an important factor in determining the values of strong motion parameters, where the direction of the rupture line plays an important role in detecting the values of strong motion parameters, the strong motion parameters and damage effects seem to be attenuated very fast in the direction perpendicular to the rupture line. This can be interpreted by the fact that the farthest accelograph lies at the extension of the fault rupture (azimuth = 30°), while the nearer one was perpendicular to the strike of the fault rupture.     

Determination of Phosphate in Saudi Arabian Waters

The procedures for the determination of phosphate are based on the reduction of molybdophosphoric heteropoly acids using ascorbic acid. Measurements of the complex products formed with rhodamine B and chlorophenol red dyes and the reduced molybdophosphoric acid are made at 490 and 510 nm with molar absorptivities of 28571 and 20949 l/mol. cm with each dye, respectively. Phosphate could be determined in the concentration ranges of 0.44 to 1.21 and 0.44 to 1.32 μg/l PO₄-P with rhodamine B and chlorophenol red dyes, respectively. The results obtained are compared with those of molybdophosphoric acid with rhodamine B and chlorophenol red using stannous chloride as reducing agent. These procedures are used for the determination of phosphate in the Kingdom of Saudi Arabia.     

Use of the subsurface thermal regime as a groundwater-flow tracer in the semi-arid western Nile Delta,Egypt

Temperature profiles from 25 boreholes were used to understand the spatial and vertical groundwater flow systems in the Western Nile Delta region of Egypt, as a case study of a semi-arid region. The study area is located between the Nile River and Wadi El Natrun. The recharge areas, which are located in the northeastern and the northwestern parts of the study area, have low subsurface temperatures. The discharge areas, which are located in the western (Wadi El Natrun) and southern (Moghra aquifer) parts of the study area, have higher subsurface temperatures. In the deeper zones, the effects of faults and the recharge area in the northeastern direction disappear at 80 m below sea level. For that depth, one main recharge and one main discharge area are recognized. The recharge area is located to the north in the Quaternary aquifer, and the discharge area is located to the south in the Miocene aquifer. Two-dimensional groundwater-flow and heat-transport models reveal that the sealing faults are the major factor disturbing the regional subsurface thermal regime in the study area. Besides the main recharge and discharge areas, the low permeability of the faults creates local discharge areas in its up-throw side and local recharge areas in its down-throw side. The estimated average linear groundwater velocity in the recharge area is 0.9 mm/day to the eastern direction and 14 mm/day to the northwest. The average linear groundwater discharge velocities range from 0.4 to 0.9 mm/day in the southern part.     

Least-cost adaptation options for global climate change impacts on the Brazilian electric power system

Global climate change induced by the emission of greenhouse gases may pose challenges to energy security. The vulnerability of energy sources, in particular of renewable sources, to climate change raises the need to identify adaptation measures. This paper applies an integrated resource planning approach to calculate least-cost adaptation measures to a set of projected climate impacts on the Brazilian power sector. The methodology used has the advantage of finding optimal solutions that take into consideration the whole energy chain and the interactions between energy supply and demand. Results point in the direction of an increased installed capacity based, mostly, on natural gas, but also sugarcane bagasse, wind power and coal/nuclear plants, to compensate for a lower reliability of hydroelectric production, amongst other impacts. The indirect effect of these results is the displacement of natural gas from other consuming sectors, such as industry, in favor of its use for power generation. Results obtained are, however, based on the techno-economic premises used in the simulation, which may vary in the long term.     

Distribution and Influence of Iron Phases on the Physico—Chemical Properties of Phyllosilicates

Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD,DTA,dissolution analysis(DCB),IR,Moessbauer and X-band Electron Spin Resonance(ESR) spectroscopies.The purity of the samples and the degree of structural order were determined by XRD.The location of Fe in the octahedral sheet is characterized by absorption bands at-875cm^-1 assigned as Al-OH-Fe which is present after chemical dissolution of free iron.The Moessbauer spectra of these clays sow two doublets with isomer shift and quadrupole splitting typical of octahedral coordinated Fe^3 ,in addition to third doubler with hyperfine parameter typical of Fe^2 in the spectra of Abu-Had kaolinite (H)sample.6-lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples.Goethite was confirmed by both IR and DTA.Multiple nature of ESR of these clays suggested structural Fe in distorted octaedral symmetry and as non-structural Fe.Little dispersion and low swelling indices as well as incomplete activaiton of investigated montmorillonite samples by NaCO3 appear to be due to incomplete disaggregation of montmorillonite particles.This can be explained by the ability of Fe-gel to aggregate the montmorillonite into pseudo-particles and retard the rigid-gel structure.However,extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples.On the other hand,amounts and site occupation of Fe associated with kaolinite samples show a negative correlation with the parameters used to describe the degree of crystalline perfection,color,brightness and vitrification range of these kaolinite samples.     

Analyse sismo-stratigraphique du bassin d'Abda (Maroc occidental), exemple de structures inverses pendant le rifting atlantiqueSeismo-stratigraphic analysis of the Abda Basin (West Morocco): a case of reverse structures during the Atlantic rifting

The review of the seismic reflection and well data from the coastal Abda Basin (western Morocco) shows that its Triassic and Jurassic sequences were deposited in a submeridean sag basin, whose eastern margin is characterised by progressive truncations and pinching out of these sequences against a prominent Palaeozoic high. The uplift of this latter is interpreted as a response to an Upper Triassic–Middle Jurassic local compressional event that controlled Triassic–Jurassic sedimentation within the Abda Basin. The present day ‘West Meseta Flexure’ is a surface expression of this uplift. To cite this article: H. Echarfaoui et al., C. R. Geoscience 334 (2002) 371–377.     

On the spectrum of a gaseous nebula of pure hydrogen

The Balmer decrement was calculated for a homogeneous, spherical, pure hydrogen nebula, ionised and excited both by radiative and collisional processes. Reabsorption in the Balmer series from sublevels 2s and 2p was taken into account. Calculations were carried out for electron temperatures of 10⁴ K and 2×10⁴ K, electron densities from 10³ to 10⁶ cm^–3, and radii from 10¹⁵ to 10¹⁷ cm. The results define allowed and forbidden regions in the log(H/H) vs log(H/H) diagram different from those of previous results obtained assuming purely radiative or purely collisional ionisation and excitation. A brief comparison with observations is presented and discussed.     

Numerical Analysis of the Behavior of A New Aeronautical Alloy (Ti555-03) Under the Effect of A High-Speed Water Jet

In this paper, we present a numerical simulation of a water jet impacting a new aeronautical material Ti555-03 plate.The Computational Fluid Dynamics(CFD) behavior of the jet is investigated using a FV(Finite Volume) method.The Fluid–Structure Interaction(FSI) is studied using a coupled SPH(Smoothed Particle Hydrodynamics)-FE(Finite Element) method. The jets hit the metal sheet with an initial velocity 500 m/s. Two configurations which differ from each other by the position(angle of inclination) of the plate relatively to the axis of revolution of the jet inlet are investigated in this study. The objective of this study is to predict the impact of the fluid produced at high pressure and high speed especially at the first moment of impact. Numerical simulations are carried out under ABAQUS. We have shown in this study that the inclination of the titanium alloy plate by 45° stimulates the phenomenon of recirculation of water. This affects the velocity profile, turbulence and boundary layers in the impact zone. The stagnation zone and the phenomenon of water recirculation are strongly influenced by the slope of the plate which gives a pressure gradient and displacement very important between the two configurations. Fluctuations of physical variables(displacement and pressure) prove the need for a noise and vibratory study. These predictions will subsequently be used for the modeling of the problem of an orthogonal cut in a high-speed machining process assisted by high-pressure water jet.