Salinization of groundwater in the Nefzawa oases region,Tunisia: results of a regional-scale hydrogeologic approach   总被引：1，自引：0，他引：1  

Mounira Zammouri  Tobias Siegfried  Tobias El-Fahem  Samiha Kriâa  Wolfgang Kinzelbach 《Hydrogeology Journal》2007,15(7):1357-1375

Groundwater pumped from the semi-confined Complexe Terminal (CT) aquifer is an important production factor in irrigated oases agriculture in southern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available from the 1980s. Water samples were taken from drains and observation wells tapping both the CT and the phreatic aquifers and analyzed with regard to chemistry, temperature, isotopes and other environmental tracers. Local salinization mechanisms are suggested, i.e. the upwelling of saline water from the underlying, confined Continental Intercalaire (CI) aquifer, as well as backflow of agricultural drainage water. At this stage, the main salt pan, the Chott el Djerid, is not a contamination source. A finite difference model was also developed to simulate groundwater flow and contaminant transport in the oases. Calibration for the period 1950–2000 was carried out in order to adjust geological and chemical system parameters. The simulation of planned extraction projects predicts a worsening of the present situation. Maintenance of the present abstraction regime will not reduce or stop the salinity increase.

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Résumé L’eau souterraine pompée dans l’aquifère semi-captif du Complexe Terminal (CT) est un facteur de production important pour l’agriculture des oasis irriguées du sud de la Tunisie. Une augmentation de la salinité de l’eau souterraine a été considérée comme la conséquence de l’augmentation des prélèvements dans l’aquifère au cours des dernières décades. Toutes les sources de contamination ont été étudiées à l’aide de données hydro-chimiques disponibles depuis les années 80. Des échantillons d’eau ont été prélevés dans des drains et des puits d’observation qui captent à la fois le CT et les aquifères phréatiques; la chimie, la température, les isotopes ainsi que d’autres traceurs environnementaux ont été analysés. Des processus locaux de salinisation sont proposés, comme par exemple la remontée d’eau salée en provenance de l’aquifère captif du Continental Intercalaire (CI) sous-jacent, ainsi que le reflux des eaux du drainage agricole. A ce stade, le principal marais salé, le Chott el Djerid, n’est pas une source de contamination. Un modèle aux différences finies a également été élaboré pour simuler les écoulements souterrains et le transport de contaminants dans les oasis. Une calibration pour la période 1950–2000 a été effectuée afin d’ajuster les paramètres des systèmes géologique et chimique. La simulation de projets planifiés d’extraction prédit une aggravation de la situation actuelle. La conservation du régime d’extraction actuel ne réduira ou ne stoppera pas l’augmentation de la salinité.

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Resumen El agua subterránea que se bombea del acuífero semi-confinado Terminal Complejo (CT) es un importante factor de producción en la agricultura de riego con oasis en el sur de Túnez. Se ha observado un incremento en la salinidad del agua subterránea como consecuencia de la abstracción creciente del acuífero durante las últimas décadas. Se investigaron todas las fuentes de contaminación usando datos hidroquímicos disponibles de la década de 1980s. Las muestras de agua se tomaron de drenajes y pozos de observación alojados tanto en el CT como los acuíferos freáticos y se analizaron en relación con química, temperatura, isótopos y otros trazadores ambientales. Se sugieren mecanismos de salinización local, i.e. el ascenso de agua salada a partir del acuífero confinado subyacente Intercalado Continental (CI), así como también retorno de flujo de agua de drenaje agrícola. En esta etapa, el pan salado principal, el Chott el Djerid, no es una fuente de contaminación. También se desarrolló un modelo de diferencia finita para simular el flujo de agua subterránea y el transporte de contaminantes en los oasis. Se calibró el modelo para el periodo 1950–2000 para de este modo ajustar parámetros del sistema químico y geológico. La simulación de los proyectos de extracción que se han planeado predice un empeoramiento de la situación actual. El mantenimiento del régimen de extracción actual no reducirá o detendrá el incremento de salinidad.

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Particulate matter dispersion and haze occurrence potential studies at a local palm oil mill     

L. C. Abdullah Ph.D.  L. L. Wong M.Sc.  M. Saari Ph.D.  A. Salmiaton Ph.D.  M. S. Abdul Rashid Ph.D. 《International Journal of Environmental Science and Technology》2007,4(2):271-278

The emissions from palm oil industry through incineration and open burning are the major sources of air pollutions contribution in Malaysia. The consequence of increasing the particulate concentration, the particulate matter dissolves with vapour and grows into droplets when the humidity exceeds approximately 70% and causing opaque situation known as haze. This work focuses on the dispersion particulate matter from palm oil mill. Gaussian Plume Model from a point source, subject to various atmospheric conditions is used to calculate particulate matter concentration then display the distribution of plume dispersion using geographic information system. Atmospheric Stability, mixing height, wind direction, wind speed, natural and artificial features play an important role in dispersion process. Study on the dispersion of particulate matters and the haze potential are presented as a case study in this paper. The data obtained will be served as the purpose of modeling the transport of particulate matter for obtaining permits and prevention of significant deterioration to the environment.  相似文献   

Letter to the editor     

Hafzullah Aksoy  N. Erdem Unal  Abdullah Gedikli 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):447-449

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Performance of a steel structure on Ar-Rayyas Sabkha soils     

Abdullah?A.?SabtanEmail author 《Geotechnical and Geological Engineering》2005,23(2):157-174

Sabkha deposits cover extensive areas along the Red Sea and the Arabian Gulf shores. They are the site of huge industrial complexes in spite of their low bearing capacity of its upper part. The strength of the Sabkha soil is controlled by several factors, among them are the evaporatic salts that cement the grains. The Standard Penetration Test (SPT) is used extensively in this terrain but its results are misleading. The Sabkha soil that may give high N value will lose most of its strength upon wetting as part of the salts are dissolved. Therefore, the design N value was adjusted for Sabkhas to account for salt migration, by relating the SPT (N) value to the Sabkha moisture and salt content. A steel structure factory that was placed in an eastern Saudi Arabian virgin Sabkha deposits was considered. After a few years of operation fresh water leaked through the ground and caused signi.cant differential collapse settlement which threatened the functional integrity of the superstructure. The differential settlement was con.ned to one area of the structure indicating that localized conditions must have contributed to the observed settlement. The subsurface conditions and the geotechnical properties of the site are presented. A statistical model was developed that quanti.es the effect of the moisture and salt content on SPT (N) values. A simple site procedure is suggested to correct the design N value in similar cases. It was found that the increase in the moisture content could reduce the SPT (N) values by as much as 60, good agreements were found between the measured and predicted N values.  相似文献   

Bacterial community and some physico-chemical characteristics in a subtropical mangrove environment in Bahrain   总被引：5，自引：0，他引：5  

Al-Sayed HA  Ghanem EH  Saleh KM 《Marine pollution bulletin》2005,50(2):147-155

A study of bacterial communities and some physico-chemical parameters of a subtropical mangrove habitat in the Arabian Gulf (Bahrain) was carried out in 1993-1994. Six stations at different parts of the tidal channel were selected for sampling. The mangrove habitat was found to harbor diverse bacterial communities, included among them anoxygenic phototrophs (AP), oxygenic phototrophs (OP), organotrophs (OT), total coliforms (TC), faecal coliforms (FC) and haloalkaliphiles (HA). Spatial and temporal variations in bacterial communities and environmental parameters were found. Each of the OT, AP, TC, and FC were dominant in the innermost stations (S1&S2) and gradually decreased seaward. The HA community on the other hand, was dominant at the seaward stations (S5&S6) and was most likely to have originated from the sea through the tidal flows. Both AP and OT were considered as part of the mangrove native flora, whereas TC and FC were alien and believed to have been introduced through partially treated sewage released at the upstream of the tidal channel. Closely monitoring of the mangrove water revealed succession pattern in bacterial communities. The AP community was predominant from November 1993 to March 1994, succeeded by dominance of OP from June 1994 to October 1994. Both bacterial blooms gave water a pinkish, purple, or green color, respectively. Although OT prevailed during Transitional period between AP and OP eutrophication, it remained comparatively constant (not less than 2 x 10(5)cfu/ml) through other periods. Frequent eutrophication phenomena of OP, which took place in summer and autumn, coincided with increases in water temperature, chlorophyll a, and nutrients (NO(3)(-) and PO(4)(-)). On the other hand, OT and AP were negatively correlated with temperature, salinity and chlorophyll a, but no specific pattern was observed in relation to NO(3)(-) and PO(4)(-). In comparison with seawater, nutrients such as NO(3)(-) and PO(4)(-) were consistently higher in the mangrove habitat. Partially treated sewage and farm drainage canals are proposed to form additional sources of nutrients. Although, the mangrove habitat has been demonstrated to possess self-cleaning properties, data obtained suggest that anthropogenic pollution has a deleterious effect.  相似文献   

The Logar ultrabasite massif and its reflection in the magnetic field (East Afghanistan)     

Abdullah Shareq  V.N. Voinov  E.B. Nevretdinov  L.V. Kubatkin  I.A. Gusav 《Tectonophysics》1980,62(1-2)

The paper deals with the structural position of the Logar ultrabasite massif with respect to the folded Kabul block. The ultrabasite is composed of a thick tectonic mantle in the ophiolite belt in the northern portion of south eastern Afghanistan. Magnetometric data together with geological investigations make it possible to understand the tectonic nature of the massif contacts.  相似文献   

Geochemical characteristics and hydrocarbon generation modeling of the Jurassic source rocks in the Shoushan Basin, north Western Desert, Egypt   总被引：1，自引：0，他引：1  

Mohamed Ragab ShalabyMohammed Hail Hakimi  Wan Hasiah Abdullah 《Marine and Petroleum Geology》2011,28(9):1611-1624

The Shoushan Basin is an important hydrocarbon province in the Western Desert, Egypt, but the origin of the hydrocarbons is not fully understood. In this study, organic matter content, type and maturity of the Jurassic source rocks exposed in the Shoushan Basin have been evaluated and integrated with the results of basin modeling to improve our understanding of burial history and timing of hydrocarbon generation. The Jurassic source rock succession comprises the Ras Qattara and Khatatba Formations, which are composed mainly of shales and sandstones with coal seams. The TOC contents are high and reached a maximum up to 50%. The TOC values of the Ras Qattara Formation range from 2 to 54 wt.%, while Khatatba Formation has TOC values in the range 1-47 wt.%. The Ras Qattara and Khatatba Formations have HI values ranging from 90 to 261 mgHC/gTOC, suggesting Types II-III and III kerogen. Vitrinite reflectance values range between 0.79 and 1.12 VRr %. Rock−Eval T_max values in the range 438-458 °C indicate a thermal maturity level sufficient for hydrocarbon generation. Thermal and burial history models indicate that the Jurassic source rocks entered the mature to late mature stage for hydrocarbon generation in the Late Cretaceous to Tertiary. Hydrocarbon generation began in the Late Cretaceous and maximum rates of oil with significant gas have been generated during the early Tertiary (Paleogene). The peak gas generation occurred during the late Tertiary (Neogene).  相似文献   

Social capital, community based management, and fishers’ livelihood in Bangladesh     

Gazi Md. Nurul Islam  Tai Shzee YewNik Mustapha R. Abdullah  K. Kuperan Viswanathan 《Ocean & Coastal Management》2011,54(2):173-180

This paper examines the impact of Community Based Fisheries Management (CBFM) on fishing households’ welfare in Bangladesh. It analyses how the various types of livelihood assets contribute to fishers’ household incomes. The study found that fishers in CBFM project areas have improved their access to different assets including social, human, physical, financial and natural capitals. The regression results show that social capital contributed significantly to household income, indicating that social factors play very important roles in poverty alleviation in Bangladesh. Future poverty alleviation policy options need to give priority to investments in human, physical and natural capital assets.  相似文献   

Gravitational instability of a non-linear magnetic fluid     

A. A. Abdullah 《Astrophysics and Space Science》1993,204(2):289-295

The problem of gravitational instability of an infinite homogenous fluid has been considered in the presence of a non-vertical magnetic field. A non-linear relation between the magnetic field and the magnetic induction proposed by P.H. Roberts (1981) in the context of neutron stars has been used. The dispersion relations have been obtained. It has been found that Jeans's criterion for instability is unaffected by this non-linear relationship even if the effect due to rotation is considered in the presence of a non-vertical magnetic field.  相似文献   

The importance of environmental science     

Abdullah R. Al-Kandari 《GeoJournal》1994,33(4):341-348

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