Pollution nitrique des eaux souterraines au Tadla (Maroc)

Dans les périmètres irrigués du Maroc, la pollution nitrique diffuse des eaux souterraines augmente le risque de détérioration de la qualité des ressources hydriques et engendre un risque sanitaire pour la population rurale s'approvisionnant le plus souvent directement de l'aquifère. La présente étude, réalisée dans le périmètre du Tadla (3600 km2), située au centre du Maroc, vise à faire l'état des lieux de la contamination des eaux souterraines par les nitrates et à identifier les causes potentielles de cette pollution.Le suivi de la concentration des eaux souterraines en nitrates a été réalisé durant la période août 1996 - avril 1998 dans un réseau de cent puits. Les paramètres du milieu physique et des pratiques culturales ont été déterminés soit par des mesures au champs, des analyses au laboratoire ou par enquête auprès des agriculteurs dans un réseau de 40 sites. Les résultats sont présentés sous forme de cartes thématiques par le SIG.Le niveau actuel de la pollution nitrique des eaux souterraines dans le périmètre irrigué du Tadla commence à devenir critique. De part la pollution ponctuelle mise en évidence aux alentours de quelques agglomérations urbaines et à l'aval des sucreries, les zones dont les teneurs en nitrates des eaux souterraines dépassent 50 mg NO3- /l sont localisées en aval des Béni Amir et en aval et à l'Est des Béni Moussa Est. Béni Moussa Ouest reste en général moins polluée que Béni Moussa Est. Les apports excessifs en eau et en engrais azotés pour les cultures pratiquées (blé, betterave, cultures maraîchères, arboriculture et luzerne), sont les causes directes de la pollution diffuse. Par ailleurs, il est certain que la texture du sol (argileuse, argilo-limoneuse et limono-argileuse), la teneur en argile (29% à 55%) et tous les paramètres qui leurs sont corrélés notamment la réserve utile du sol, réduisent le risque de lixiviation des nitrates en profondeur et assurent en conséquence un contrôle naturel de la pollution nitrique des eaux souterraines. Néanmoins, tous les autres facteurs étudiés notamment le niveau des nappes faible par rapport au sol (<4m-12m), la vitesse d'infiltration du sol en milieu saturé généralement élevée (20-450 mm/h), les teneurs assez importantes du sol en matière organique (1.5%-3.5%) et en azote total (0.10%-0.15%), joueraient positivement sur la vulnérabilité de la nappe à cette pollution. De même, le pouvoir de minéralisation élevé des sols couplé aux conditions écologiques favorables à une minéralisation intense de la matière organique native du sol, assez caractéristique des régions irriguées à climat méditerranéen, seraient en partie responsable de cette pollution. Néanmoins, Aucune corrélation n'a été mise en évidence entre la teneur en nitrate des eaux souterraines et les combinaisons linéaires des variables du milieu physique. Ceci serait dû à l'homogénéité du milieu physique et à l'accumulation de la pollution suivant le sens d'écoulement des nappes de l'amont vers l'aval hydraulique. Vu le niveau d'intensification agricole que connaît cette région, la situation risquerait de s'aggraver rapidement induisant, en dehors de toute mesure de prévention, la détérioration de la qualité des eaux souterraines dans cette région.In Morocco, diffuse ground water pollution by nitrates in irrigated areas has caused an increase in the risk of water quality deterioration. This has generated a health risk in rural areas, since most of the rural population get their drinking water supply from the aquifer. The present study was carried out in the Tadla region. The plain of Tadla is situated in the centre of Morocco, in the Oum Erbia river basin. It covers a surface area of 3600 km2. The Oum Erbia river (160 km long) divides this plain into two large irrigated areas (Beni Amir in the east (3300 ha) and Beni Moussa in the south (6900 ha)), with different hydrological characteristics. The irrigation water comes from the Oum Erbia river, the Bin El Ouidane dam and from two important waters tables: Beni Amir (190 Mm3) and Beni Moussa (250 Mm3). The objectives of this study were to quantify the degree of ground water contamination by nitrates and to identify the potential causes of this pollution.The monitoring of nitrate concentrations in ground water was carried out during the period of August 1996 to April 1998, in 100 wells in the region of study. The physical environment and agricultural practices were determined either by field measurements, laboratory analyses or by investigations with farmers at 40 selected sites. The results are presented by thematic maps using a geographical information system.The level of ground water nitrate pollution is becoming a serious problem. The point pollution is localized around or downstream of urban built up areas such as Fquih Ben Saleh, Beni Mellal, Souk Sebt and Oulad Ayad. This pollution, caused by household wastes, is likely aggravated by waste dumping from the sugar refineries (SUBM, SUTA and SUNAT) as well as by waste water reuse in agriculture. Other zones with nitrate concentrations more than 50 mg NO3 -/L were observed in wells situated downstream from Beni Amir and east of Beni Moussa. West Beni Moussa was generally not as polluted as east Beni Moussa, but an increase in ground water nitrate levels was observed in some downstream wells in west Beni Moussa. The diffuse nitrate pollution has been attributed to land use, irrigation and fertilization practices. These practices may be responsible for nitrate leaching beyond the root zone during the cropping season and may generate large quantities of residual inorganic nitrogen at harvest time. This represents a potential risk of nitrate ground water pollution in the next draining period. The physical characteristics of soil texture (clay, clay-silt and silty clay), percentage clay (29 % - 55 %) and their correlated parameters (especially the useful storage capacity) act to reduce the risk of nitrate leaching and ensures a control on ground water nitrate pollution. However, other observations including: a low water level table compared to the soil surface, particularly in the middle of the irrigated area and around the edge of the Oum Erbia river (<4 - 12m); a high soil infiltration rate in unsaturated soil, which varied from 20 -100 mm/h (permeable soils) to 200 - 450 mm/h (extremely permeable soils); a high level of organic matter in the soil (1.5% - 3.5%) and; total nitrogen contents (0.10% - 0.15%) would increase the aquifer vulnerability to ground water nitrate pollution. Similarly, the high soil mineralization capacity in the 0-60 cm soil layer (100 - 600 kg N /ha), combined with the ecological conditions, favoured an intense mineralization of the native organic matter of soil. This high mineralization capacity, which is characteristic of irrigated Mediterranean areas, could be partly responsible for this pollution. However, no correlation was found between ground water nitrate contents and linear combinations of physical environmental variables. This could be due to the homogeneity of the physical environment and to the movement of water in the saturated soil, in the direction of ground water flow, inducing the accumulation of nitrate pollution in the hydraulic downstream area of the water table.Considering the degree of agriculture in this area, the situation could worsen rapidly, thus inducing significant ground water deterioration. In attempts to avoid this situation, many important measures at the regional scale are necessary, in order to rationalize agricultural practices and to increase the farmers' awareness of ground water nitrate pollution. These urgent preventative actions should be adopted in order to combine agricultural productivity and durability with water economy and water quality preservation. Some programs are in progress within this region. The objectives are essentially to reduce nitrate excess and to introduce more efficient irrigation techniques such as the pivot (frontal ramp) recommended for cereals and sugar beet, and localized irrigation system proposed for vegetable crops and arboriculture. Also, since the Oum Erbia river basin has also been subjected to a clean-up of urban and industrial pollution, it would be interesting to carry out a more precise study of nitrogen dynamics and nitrate leaching at the plot scale, especially for the most common practiced crops in the region (wheat, sugar beet and vegetable crops). This would advance the understanding and management of nitrogen cycles in the crop-water-soil system.Finally, the database included as part of this study may be integrated in a water and nitrate movement simulation model. This will allow the prediction of nitrate leaching losses and identify, through scenario analysis, the links that should be acted on, in order to reduce the risk of ground water nitrate pollution in this region

Fertilisation azotée du blé dur (Triticum durum Desf L.) en irrigué dans les Doukkala (Maroc)

Cette étude multi-site a pour objet de déterminer les équations nécessaires au raisonnement de la fertilisation azotée du blé dur en irrigué dans les Doukkala. La variété "Marzak" a été utilisée. En 1992-93, huit essais dose d'azote ont été conduits (0, 60, 120, 180 kgN/ha). En 1993-94, trois essais combinant les densités de semis et les niveàux d'azote ont été réalisés. Les résultats ont montré que les réponses aux apports d'azote dépendaient de la fertilité initiale du sol. En 1993-94, l'augmentation de la densité de semis aboutit a une amélioration du rendement grain. Une équation de calcul de la dose d'azote à apporter qui tient compte de la différence entre le rendement visé et celui du témoin sans azote, l'efficience de l'azote absorbé (ENA) et le taux de recouvrement apparent de l'engrais (TR) a été établie. Le rendement du témoin sans azote a été hautement corrélé à la teneur en azote nitrique initiale, au taux de matière organique et à la teneur en azote obtenue en conditions d'anaérobie à 40°C. Le TR diminue avec l'augmentation de la quantité d'azote apportée, l'ENA est constant avec une moyenne de 3.5 kgN/100 kg de grain

Study the effect of echinacea purpurea extract on cellular delayed type hypersensitivity and splenocyte proliferation in BALB/c mice

Objective: Purple cone flower plant (Echinacea purpurea) is one of the most important Herbal products in many countries. Up to now a lot of experiments demonstrated the controversial effects of this herb on immune system . In this research we study the in vivo and in vitro effect of Iranian E.purpurea extract on cellular immunity. Materials and Methods: At first we determined the lethal dose of E.purpurea extract after intraperitoneal injection in BALB/c mice. Then we made five groups of mice and treat them by four times intraperitoneal injection of 1 ml extract at different doses (0, 0.4, 2, 10 and 50 mg/ml) during two weeks. Splenocyte proliferation response to extract was assessed by MTT method. Delayed-Type Hypersensitivity (DTH) response was evaluated by priming mice with 1×108 Sheep Red Blood Cell (SRBC) injected subcutaneously in the back on day 7after treatment. Results: As a result no significant variation in weight and spleen index of test groups to control was observed. Splenocyte proliferation and DTH response of test groups to control increased significantly (p<0.05). Conclusion: However these data confirmed the results of previous studies, in addition presented the first results about significant increase in DTH response that could not be seen before. Scince the main reason of this difference refers to active compounds of herb extract, comparing effective component of this extract with that of E.purpurea cultivated in other geographical condition will consider as the next studies

Polarization and its discontents: Morocco before and after the Arab Spring

This paper uses data obtained from three Moroccan household surveys that took place between 2000 to 2013, to address issues related to the so-called "Arab puzzle". Welfare inequalities are low and declining in Arab countries and exist against the backdrop of a growing sense of dissatisfaction and frustration. The paper hypothesizes that welfare inequality plays a role, if seen through the lens of absolute measures and notably absolute polarization. The paper argues that the relatively worse perception of poor, vulnerable, and lower middle-class Moroccan households mirrors the ongoing hollowing out of the welfare distribution process and its concentration in the tails. The results of a multi-logit regression indicate that polarization is significantly correlated to perception and, importantly, that this correlation is asymmetric. The poorer are the households, the more polarization is perceived to link negatively to the well-being of households; and the richer are the households, the more polarization will positively correlate with their perceived well-being. The results are robust to the use of classes or quintiles for ranking social groups from the poorest to the richest

Selection for growth in Coturnix coturnix japonica on a low protein ration

Several experiments were carried out on Coturnix coturnix japonica to investigate the effect of selection for growth on a protein deficient ration. A level of 27% protein was found to be optimum for three different strains and 17.8% was the lowest protein level used that allowed for growth and accordingly this latter level was chosen as that on which to carry out selection. Despite the fact that a statistical analysis showed no difference between three strains, strain 908 was chosen on the basis of the slightly better two-week body weight on the deficient diet as well as for the fact that management facilities did not permit continuing selection with all three strains. The apparent lack of response to mass or individual selection led to the adoption of progeny testing as a basis for selection. Two weeks on the deficient diet immediately upon hatching was not found to be significantly different from a selection standpoint from one week on the normal diet followed by two weeks on the deficient diet. Notwithstanding the lack of difference, the former was chosen because it allowed economy of time and also a lower incidence of a crop disorder observed in the course of the investigations. A maximum response for two-week body weight of 7.6 gms was observed after six series of matings over the control line. Heritability estimates for growth on a deficient diet based on full-sib analysis were 0.17, 0.62 and 0.39 for sire, dam and combined components, respectively, and 0.18 from parent-offspring regression in the selected line. Realized heritability was 0.16. Maternal and non-additive genetic effects were deemed to be important factors of variation in growth. Egg weight increased by two grams as a correlated response to selection for two-week body weight. The sixth series showed the most notable changes. Fertility and hatchability decreased by 10% from the fifth to the sixth series and inbreeding which was negligible for the most part increased by 0.1 in the last series. A significant genetic-environmental interaction in the incidence of pendulous crop was noted. The incidence of this defect was successfully increased by selection of affected birds. The condition was apparently brought on by an increased water consumption induced by a high sugar (cerelose) level in the diet. Special emphasis was placed on determining whether selection was for a specific resistance to the protein deficiency rather than for an overall superior growth rate. As a result of the apparent failure in the selection for a specific resistance to protein deficiency through six series of matings and in view of a similar difficulty encountered by investigators who worked with chickens, it is suggested that perhaps tissue amino acid analysis or perhaps enzyme activity in the selected line may be more sensitive criteria than body weight under such experimental conditions

Echinacea purpurea polysaccharide reduces the latency rate in herpes simplex virus type-1 infections

Objective: During the latency period of herpes simplex virus type-1 (HSV-1), the virus can occasionally reactivate, travel back to the eye and cause recurrent ocular disease. As this condition arises from the ability of HSV-1 to produce a dormant infection, effective medication to prevent the virus enter a latent state should prevent it. In this study, we applied Echinacea polysaccharide (EP) fraction as prophylactic mediator for latency prevention. Methods: In order to investigate the protective properties of EP, we evaluated its immunostimulatory functions on different immune aspects that play important roles in latency prevention (particularly IFN-γ as one of the main indicators of cellular immunity and latency). Finally, we assessed establishment of latency by detection of thymidine kinase gene in trigeminal ganglia of BALB/c mice. Results: We demonstrated that EP promotes immune response, leading to a reduced latency rate, and it has a promising effect on latency prevention. Conclusion: EP was able to exert an antiviral action on the development of recurrent HSV-1 disease when supplied prior to infection. © 2009 S. Karger AG, Basel