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Belkhodja H.,Institute Superieur Of Peche Et Daquaculture Of Bizerte | Romdhane M.S.,Institute National Agronomique Of Tunis
Cahiers de Biologie Marine

The limpets Patella caerulea was evaluated as possible biomonitor of heavy metal contamination in marine coastal areas. Water samples and specimens of the limpet were sampled seasonally during 2006-2007, from three different stations in the North coasts of Tunisia (Bizerta Channel: CB, La Goulette: LG and Sidi Rais: SR) to measure their accumulated heavy metal concentrations. The concentrations of Fe, Mn, Cu, Cd, Cr, Ni, Al and Pb were determined by ICP-OES methods. In water samples, only 3 metals (Mn, Cu and Al) were detected at different stations while in the limpet all the investigated metals were found. Iron and Aluminium concentrations in soft tissues of P. caerulea were significantly higher (ANOVA, p < 0.05) than the concentration of the other metals in all the stations while the lowest one was cadmium concentration. The order of metal accumulation in the animal at different stations was: Fe >> Al >> Mn - Cu > Ni - Pb > Cr > Cd. The highest mean values of the heavy metals in soft tissues of P. caerulea were found at CB station, for Cd, Cr and Fe. We also noticed at the same station relatively high mean values for Ni, Al and Pb; at LG station, for Mn, Cu and Pb and at SR station for Al. Source

Kouzana L.,University of Tunis | Benassi R.,University of Tunis | Ben mammou A.,University of Tunis | Sfar felfoul M.,Institute National Agronomique Of Tunis
Journal of African Earth Sciences

Coastal aquifers serve as major sources for freshwater supply in many countries around the world, especially in arid and semi arid zones. The fact that coastal zones contain some of the densely populated areas in the world makes the need for freshwater even more acute. The intensive extraction of groundwater from coastal aquifers reduces freshwater outflow to the sea and creates local water aquifer depression, causing seawater migration inland and rising toward the wells. This phenomenon, called seawater intrusion, has become one of the major constraints imposed on groundwater utilization. As seawater intrusion progresses, existing pumping wells become saline and have to be abandoned.In this paper, we have the results of the seawater intrusion study of the Korba aquifer by the geophysical and hydrochemical methods. In order to locate the zones affected by saltwater intrusion, 38 Vertical electrical sounding (VES) were distributed over the coastal area between Korba and Oued Lebna. The interpretation of these electric soundings using Winsev software, based on mechanical boreholes, carry out iso-resistivity and iso-depth maps of seawater intrusion. The maps of apparent iso-resistivity having different lengths of line and the pseudosections differentiate dry grounds, grounds saturated with fresh water and those saturated with brackish water and saltwater. Mapping of the boundaries between freshwater and saltwater is an ideal application for resistivity surveys because of the high electrical conductivity of the saltwater and its contrast with that of fresh water. The correlation of the different electric surveys allowed realizing geo-electric sections showing the vertical configuration of seawater intrusion. It comes out from this study that saltwater intrusion reached approximately a distance of 3. km inland.The high groundwater salinity anomaly observed in Diar El Hajjej, Garaet Sassi and Takelsa-Korba zones was explained by the presence of seawater intrusion in these areas. This hypothesis is based on high chloride concentrations, the inverse cationic exchange reactions, and the lower piezometric level compared to sea level. © 2010 Elsevier Ltd. Source

Belkhodja H.,Institute Superieur Of Peche Et Daquaculture Of Bizerte | Jaafoura M.H.,Institute Mohamed Kassab DOrthopedie | Missaoui H.,Direction Generale de la Peche et de LAquaculture de Tunis | Romdhane M.S.,Institute National Agronomique Of Tunis
Cahiers de Biologie Marine

This study devised a staging system for and monitored the gonad development of the limpet Patella caerulea in La Goulette harbour (Gulf of Tunis) using a Gonad Somatic Index (GSI) and histological techniques. Sex ratio varied along the study period, where samples always presenting more males than females. Maturation began in August/September for both sexes. In males, spawning took place from March to August 2006 and from April to June 2007. Regarding females, spawning took place from May to July 2006 and from April to July 2007. A secondary spawning peak was observed in January 2007 for both sexes. No statistical differences were registered between GSI of both sexes; however, the use of the GSI in determining the annual reproductive cycle is discussed. High wind speed under optimum conditions of temperature and salinity appear to induce spawning in the limpets. Source

Khomsi S.,CNRS Georesources lab | Khomsi S.,King Abdulaziz University | Echihi O.,ETAP | Slimani N.,Institute National Agronomique Of Tunis
Comptes Rendus - Geoscience

A set of different data including high resolution seismic sections, petroleum wire-logging well data, borehole piezometry, structural cross-sections and outcrop analysis allowed us to characterise the tectonic framework, and its relationships with the deep aquifers seated in Cretaceous-Miocene deep reservoirs. The structural framework, based on major structures, controls the occurrence of deep aquifers and sub-basin aquifer distributions. Five structural domains can be defined, having different morphostructural characteristics. The northernmost domain lying on the north-south axis and Zaghouan thrust system is a domain of recharge by underflow of the different subsurface reservoirs and aquifers from outcrops of highly fractured reservoirs. On the other hand, the morphostructural configuration controls the piezometry of underground flows in the Plio-Quaternary unconfined aquifer. In the subsurface the Late Cretaceous-Miocene reservoirs are widespread with high thicknesses in many places and high porosities and connectivities especially along major fault corridors and on the crestal parts of major anticlines. Among all reservoirs, the Oligo-Miocene, detritic series are widespread and present high cumulative thicknesses. Subsurface and fieldwork outline the occurrence of 10 fractured sandy reservoirs for these series with packages having high hydrodynamic and petrophysical characteristics. These series show low salinities (maximum 5. g/l) in the northern part of the study area and will constitute an important source of drinkable water for the next generations. A regional structural cross-section is presented, compiled from all the different data sets, allowing us to define the major characteristics of the hydrogeological-hydrogeothermal sub-basins. Eight hydrogeological provinces are defined from north-west to south-east. A major thermal anomaly is clearly identified in the south-eastern part of the study area in Sfax-Sidi Il Itayem. This anomaly is possibly related to major faults pertaining to the Sirt basin and controlled by a deep thermal anomaly. Many exploration targets are identified especially along the Cherichira-Kondar thrust where the Oligocene subcropping reservoirs are well developed. They are highly fractured and show good hydrodynamic characteristics. © 2012 Académie des sciences. Source

Zened A.,French National Institute for Agricultural Research | Zened A.,National Polytechnic Institute of Toulouse | Troegeler-Meynadier A.,French National Institute for Agricultural Research | Troegeler-Meynadier A.,National Polytechnic Institute of Toulouse | And 3 more authors.
Journal of Dairy Science

Among trans fatty acids, trans-10,. cis-12 CLA has negative effects on cow milk fat production and can affect human health. In high-yielding dairy cows, a shift from the trans-11 to the trans-10 pathway of biohydrogenation (BH) can occur in the rumen of cows receiving high-concentrate diets, especially when the diet is supplemented with unsaturated fat sources. In some but not all experiments, vitamin E has been shown to control this shift. To ascertain the effects of vitamin E on this shift of BH pathway, 2 studies were conducted. The first study explored in vitro the effects of addition of natural (RRR-α-tocopherol acetate) and synthetic (dl-α-tocopherol acetate) vitamin E. Compared with control and synthetic vitamin E, the natural form resulted in a greater trans-10/. trans-11 ratio; however, the effect was very low, suggesting that vitamin E was neither a limiting factor for rumen BH nor a modulator of the BH pathway. An in vivo study investigated the effect of natural vitamin E (RRR-α-tocopherol) on this shift and subsequent milk fat depression. Six rumen-fistulated lactating Holstein cows were assigned to a 2 × 2 crossover design. Cows received 20-kg DM of a control diet based on corn silage with 22% of wheat, and after 2 wk of adaptation, the diet was supplemented with 600 g of sunflower oil for 2. more weeks. During the last week of this 4-wk experimental period, cows were divided into 2 groups: an unsupplemented control group and a group receiving 11 g of RRR-α-tocopherol acetate per day. A trans-10 shift of ruminal BH associated with milk fat depression due to oil supplementation of a high-wheat diet was observed, but vitamin E supplementation of dairy cows did not result in a reversal toward a trans-11 BH pathway, and did not restore milk fat content. © 2012 American Dairy Science Association. Source

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