Eutrophisation des eaux des retenues des barrages Smir et Sehla (maroc) : causes, conséquences et consignes de gestion

Au Maroc, plusieurs retenues de barrages connaissent des problèmes de la dégradation de leur qualité d'eau due essentiellement aux différentes sources de pollution. L'une des conséquences de cette situation est l'enrichissement de l'eau par les nutriments (N et P) indicateur d'un état avancé de l'eutrophisation. Ce phénomène provoque un déséquilibre de l'écosystème avec un développement anarchique d'algues et une consommation intense de l'oxygène au fond des lacs.La Direction de la Recherche et de la Planification de l'Eau a conduit depuis la fin des années 80 un programme de surveillance de la qualité des eaux des retenues de barrage dans le but de proposer des solutions pour réduire ses conséquences.Le présent travail consiste à présenter les résultats de l'eutrophisation des eaux de deux retenues de barrages : Smir située au Nord du Maroc qui sert à alimenter la zone côtière entre Tétouan et Sebta en eau potable, et Sahla située au Nord-Est du Maroc qui sert à alimenter la ville de Taounate en eau potable et protéger la grande retenue Al Wahda contre l'envasement et l'eutrophisation.Les résultats concernent l'exploitation des données physico-chimiques et biologiques selon un profil vertical de profondeur. Entre 1993 et 1998 pour Smir et entre 1996 et 1998 pour Sahla.Les paramètres physico-chimiques, transparence et phosphore total ne semblent pas être de bons descripteurs de la qualité des eaux de ces retenues se trouvant dans les zones semi-arides du fait de l'importance de la charge solide particulaire non bio-disponible pour le phytoplancton. Par contre la concentration en chlorophylle a semble être représentative du niveau trophique puisqu'elle donne une idée réelle du développement algale.Un état trophique des deux lacs réservoirs est dressé, et une comparaison de la qualité des eaux est faite en tenant compte des différentes mesures prises par le gestionnaire de la ressource en eau pour atténuer le phénomène de l'eutrophisation.In Morocco, many reservoirs have known water quality problems due to the different pollution sources to which they are subjected. One of the consequences of this situation is the enrichment of the water by nutrients (such as phosphorus and nitrogen), leading to eutrophication. This phenomenon causes ecological imbalance with an excessive development of algae and a high oxygen demand in the bottom of lakes.Since the end of the 1980s, the Directorate of Water Research and Planning has been conducting a water quality monitoring program in reservoirs to understand the eutrophication phenomenon and to suggest solutions in order to reduce its possible impacts.In this paper we present the results of a case study of eutrophication in two reservoir lakes: the Smir reservoir, located in northern Morocco with a capacity of approximately 43 million m3, and the Sahla reservoir, located in north-eastern Morocco with a capacity of approximately 62 millions m3. The Smir reservoir is used to supply potable water for the northern coastal region, whereas the Sahla reservoir supplies potable water to the city of Taounate and as well protects the reservoir Lake Al Wahda.The results comprise a data set for a special experimental water quality monitoring program intended to monitor the evolution of physical, chemical and biological parameters along a vertical profile at the deepest point of the reservoirs. Samples were collected from 1993 to 1998 for Smir, and from 1996 to 1998 for Sahla.The physical-chemical, transparency and total phosphorus parameters do not appear to reflect the trophic status for these reservoir lakes located in the hot regions of semiarid areas. Indeed the solid particles were not bio-available for phytoplankton. However the chlorophyll concentration appears to be representative and indicative of increases in algal growth. The trophic state of the two reservoir lakes was addressed and a comparison of water quality was carried out in relation to different considered measurements

Wet synthesis of high purity crystalline urea phosphate from untreated Moroccan industrial phosphoric acid

The phosphorus-nitrogen fertilizer family improves the availability of phosphorus and nitrogen for efficient crop growth. Urea phosphate 17-44-0 (N-P2O5-K2O%) is considered as a binary fertilizer characterized by its high purity and it is easily soluble in water. In addition, urea phosphate can be used in other fields as a high-quality food additive, finishing agent for metals and fermentation food. As a fertilizer, it is suitable for alkaline soils.In this work, a new process for the synthesis of urea phosphate by the wet route is developed. It consists in directly producing crystalline urea phosphate by the chemical reaction between Moroccan industrial phosphoric acid (54 % P2O5) and solid urea (46 %). The synthesis is carried out by mixing the solid urea with a stoichiometric amount of untreated Moroccan industrial phosphoric acid. The chemical reaction is complete for optimal conditions which are a temperature of 50 °C and a duration of 90 min. After cooling, the urea phosphate crystals are formed without any additional treatment and are easily recovered. Analysis of the residual liquor after recovery of the urea phosphate crystals confirms that the majority of impurities which may be harmful to the environment pass into the liquid phas

Optimization of conditions to convert phosphogypsum into Ca(OH)2 and Na2SO4

With a view to finding solutions to the problems of Moroccan phosphogyosum (PG) in the long term, a research theme has been developed in our laboratory on the valorization of this residue by its conversion into marketable products by soft chemistry way less expensive. Thus, we investigated the optimal experimental conditions allowing a good efficiency of PG conversion by using NaOH to synthesize marketable products such as Ca(OH)2 and Na2SO4 of high purity. We varied the reagent concentrations and the attack durations to optimize these conditions. The quality of the products obtained is checked by XRD, IR and ICP to determine the distribution of PG impurities between obtained products. The morphology and size distribution were also established by SEM and laser granulometry

Modified differentials and basic cohomology for Riemannian foliations

We define a new version of the exterior derivative on the basic forms of a Riemannian foliation to obtain a new form of basic cohomology that satisfies Poincar\'e duality in the transversally orientable case. We use this twisted basic cohomology to show relationships between curvature, tautness, and vanishing of the basic Euler characteristic and basic signature.Comment: 20 pages, references added, minor corrections mad

Efficacy of a combination of N-palmitoylethanolamide, beta-caryophyllene, carnosic acid, and myrrh extract on chronic neuropathic pain: A preclinical study

Neuropathic pain (NP) is a common public health problem that poses a major challenge to basic scientists and health-care providers. NP is a complex problem with an unclear etiology and an often-inadequate response to current medications. Despite the high number of drugs available, their limited pharmacological efficacy and side effects hamper their chronic use. Thus, the search for novel treatments is a priority. In addition to pharmaceuticals, natural extracts and food supplements are often used to help treating patients with NP. One such supplement is Noxiall®, a commercially available combination of N-Palmitoylethanolamide (PEA), beta-caryophyllene; carnosic acid and myrrh. Here, we compare the efficacy of Noxiall® to that of the medications gabapentin and pregabalin in the NP model of chronic constriction injury (CCI) using sciatic nerve ligation in mouse. Following CCI, mice developed a significant increase in mechanical allodynia and thermal hyperalgesia. Results showed that administration of either Noxiall®, pregabalin, or gabapentin significantly attenuated mechanical allodynia. The magnitude of the Noxiall® effect was comparable to that of gabapentin or pregabalin. In addition, co-administration of non-effective doses of pregabalin and Noxiall® resulted in a significant decrease in NP, suggesting an additive efficacy. Noxiall® was efficacious also in reducing CCI-induced thermal hyperalgesia. These findings support the rationale of using natural remedies in conjunction with classical pharmacological agents to treat chronic NP

Synthesis and antimicrobial activity of some quinoxaline derivatives

Some new structural motifs containing the quinoxaline nucleus have been synthesized and examined for their pharmacological properties. In this study, 6-chloroquinoxaline-2,3(1H, 4H)-dione and 6 nitroquinoxaline-2,3(1H, 4H)-dione were synthesized as basic nuclei for the preparation of the new quinoxaline-2,3-diones by alkylation reactions under the conditions of phase transfer catalysis. The products were characterized by spectroscopic methods 1H and 13C NMR. Then, the synthesized products were tested for their antibacterial effects against two bacterial strains. The values of minimum inhibitory concentrations (MIC) vary according to the nature of the alkyl bonded to the quinoxaline nucleus

Structural study, thermal and physical properties of K2O-CaO-P2O5 phosphate glasses

Glasses of 50P2O5-xCaO-(50-x)K2O  (x= 0, 10, 20, 30, and 40 mol %) compositions were synthesized using the melt-quench procedure. The amorphous character of the prepared material was confirmed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Fourier Transform Infra-Red (FT-IR) and Raman spectroscopy are also carried out in order to determine the structural network evolution of the glassy materials with the composition. Besides, the physical properties of the glassy phosphate system were examined such as density and molar volume. The results showed that the increase of CaO content in phosphate glasses diminish the molar volume and raise the density and transition temperature. FTIR and Raman spectroscopy analysis demonstrate the formation of P-O-Ca bonds that substitute P-O-K bonds and the depolymerization of the phosphate chains. The formation of P-O-Ca bonds is in accordance with variations of glass transition temperature, (Tg), molar volume (Vm) and density (ρ). The former bonds are the origin of the partial glass-forming ability of Ca2+. In addition, an analysis of the surface morphology features was conducted using a Scanning Electron Microscopy (SEM) technique

First Exclusive Measurement of Deeply Virtual Compton Scattering off \u3csup\u3e4\u3c/sup\u3eHe: Toward the 3D Tomography of Nuclei

We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized 4He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling 4He nuclei. We measure beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we are able to extract, in a model-independent way, the real and imaginary parts of the only 4He Compton form factor, HA. This first measurement of coherent deeply virtual Compton scattering on the 4He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei