Environmental Impact Assessment of a Flood Control Channel in Sfax City, Tunisia

The objective of this study is to evaluate water and sediment quality in the southern branch of a flood control channel in Sfax city, as well as its neighboring sites. This artificial channel, located 4km away from downtown Sfax, was implemented in 1984 to protect the city against floods. Even though it contributed to reduce the harmful flood effects, this channel also resulted in new environmental problems that may cause a public health threat. Indeed, artificial surfaces pose a greater risk of infection due to bacteria, fungi and other microorganisms. A total of 19 water samples (9 from the channel and 10 from groundwater wells) were collected in a dry period and analyzed in the laboratory. Furthermore, 12 sediment samples were taken from the bottom of the channel. Water quality data were used to examine the spatial variability of the different water quality parametrs. The resultant maps revealed an important contamination and illustrated that the degree of contamination differs from one site to another, depending on the distance from the pollution source (industrial, domestic or agricultural activity), the depth of the groundwater table and also the maintenance of the well and its surroundings

Environmental Impact Assessment of a Flood Control Channel in Sfax City, Tunisia

The objective of this study is to evaluate water and sediment quality in the southern branch of a flood control channel in Sfax city, as well as its neighboring sites.  This artificial channel, located 4km away from downtown Sfax, was implemented in 1984 to protect the city against floods. Even though it contributed to reduce the harmful flood effects, this channel also resulted in new environmental problems that may cause a public health threat. Indeed, artificial surfaces pose a greater risk of infection due to bacteria, fungi and other microorganisms. A total of 19 water samples (9 from the channel and 10 from groundwater wells) were collected in a dry period and analyzed in the laboratory. Furthermore, 12 sediment samples were taken from the bottom of the channel. Water quality data were used to examine the spatial variability of the different water quality parametrs. The resultant maps revealed an important contamination and illustrated that the degree of contamination differs from one site to another, depending on the distance from the pollution source (industrial, domestic or agricultural activity), the depth of the groundwater table and also the maintenance of the well and its surroundings

Surface sediment dynamics along the eastern coast of Djerba Island (Gabes Gulf, Tunisia)

International audienceSurface sediment dynamics were studied on the eastern coast of Djerba Island (Gabes Gulf, southern Tunisia) by simultaneously assessing currents, as well as the mineralogy and grain size of bottom sediments. Harmonic analysis of time-series sea data at Ras Taguermess and El Kantara illustrated the dominance of a semi-diurnal tidal component, with a period of 12h 42min. Orthogonal Empirical Functions analysis of tidal currents along the major axis at El Kantara produced a standard deviation of +45 cm s−1 with a main angle of 29°, whereas at Ras Taguermess it was 5 cm s−1 with a north-south direction. Analysis of grain sizes from sediment samples taken between Ras Taguermess and Ras Marmour show that the shallow bottoms (0–10 m) are composed of fine, medium and coarse sands. Mean grain size ranges between 100 and 763 μm, a distribution attributed to a high level of wave activity. Moreover, two mean grain size gradients were evidenced: the first is alongshore from north to south, from Ras Taguermess to Aghir, and the second from south-east to north-west, between Ras Marmour and Bin El Ouediane. Quartz is abundant from Ras Taguermess to Sidi Garous along the many beaches, while it quantitatively decreased in the eroded area between Sidi Garous and Aghir. Thus, transport is from north to south. A high build-up of sediment was observed in Bin El Ouediane, resulting from a barrier island formation

Surface sediment dynamics along with hydrodynamics along the shores of Tunis Gulf (north-eastern Mediterranean).

International audienceThe authors report on a study conducted as a part of a project to favour sustainable management of coastal zones, investigating hydrodynamics, sediment dynamics, grain size and mineral composition of surface sediment in Tunis Gulf. Currents, winds and waves affect the erosion, transport and deposition of particles along the coast, leading to an unbalanced sediment budget. Currents recorded in the coastal areas of Port au Prince and Ghar El Melh have an average speed 12 cm s−1 during summer but exceeding 20 cm s−1 in the case of short strong winds. Numerical simulations of current velocities in the Gulf of Tunis were conducted in both summer and winter. Current velocities reached 20 cm s−1 and 10 cm s−1 in winter and summer, respectively.The results of grain-size and mineralogical analyses of surface sediments collected at various depths between Sidi El Mekki and Cap Bon (Tunis Gulf) led to identification of their origin, essentially via transport and deposit. Granulometric study showed that detritus materials in the gulf are of continental origin, while mineralogical analyses revealed a clear relationship between recent sedimentary stock from the gulf and the bordering geological formations. As all sediment distribution is controlled by water movement, a high fraction of fine sediments (>90%) is transported by the major Mediterranean currents and deposited in the gulf’s central zone. Coarse sediments, on the other hand, are found at the gulf’s entrance in the vicinity of Ghar El Melh Lagoon and, more generally, along the gulf’s western shore as a result of littoral transport under wave and swell action

Surface sediment dynamics along the shore of Hammamet Gulf (Tunisia, southern Mediterranean)

International audienceIn the summer of 2015 the authors analysed grain size and surface sediment composition through high spatial resolution from samples taken at 53 stations along the Hammamet coast (southern Mediterranean Sea). The Acoustic Doppler Current Profiler deployed in this study showed that the surface current flows toward the north-east, parallel to the coast at a maximum speed along the main axis of about 5.9 cm s−1. Near the bottom the current flows toward the north-west at a maximum speed of 2.2 cm s−1. The tide plays a relatively small role in water circulation in Hammamet Gulf. Spatial distribution of particle size, along with speed and current direction analysis, furnish an overview of the gulf’s sediment dynamics and transport. The sands are categorised as moderately sorted, well sorted or very well sorted. Particle size distribution of surface sediments from the coast to a depth of 25 m offshore shows a decreasing trend in the offshore direction. Mineralogical analysis shows that Hammamet’s coastal sands are composed of two main minerals: quartz and calcite. Magnesium calcite and aragonite are present in small amounts.Sediment dynamics along the Hammamet Gulf shores are complex, being subject to the effect of swells and secondarily of tides. We encourage the implementation of responsible environmental management procedures in order to help preserve the site

Assessment of surface sediment dynamics and response of benthic macrofauna assemblages in Boughrara Lagoon (SW Mediterranean Sea)

International audienceA study was conducted in the spring of 2009, the winters of 2010 and 2013, and in the summer of 2012 at 13 stations in Boughrara Lagoon, Tunisia (southern Mediterranean). The country’s largest lagoon, it is considered to be an anthropogenically stressed area, though a major tourist centre—Djerba Island—is located along its northern shores. The lagoon bottoms were studied via analyses of grain size, surface sediment composition, total organic matter (TOM) and through the trophic and functional organisation of benthic macrofauna. The results indicate that the bottoms are composed of fine, medium or coarse sands and that sediment distribution is controlled by water movement. Estimation of TOM content revealed that the studied samples present both normal and imbalanced sediments. The structure and organisation of the lagoon’s benthic macrofauna are dominated by select deposit feeders and underwent significant changes during the period 2010–2013.Subjected for decades to increased pollution due to growing human activities in the surrounding area, Boughrara Lagoon now appears to be impacted by certain environmental/anthropogenic stressors, as indicated by the presence of pollution-tolerant bio-indicator species in the imbalanced area. The response of the lagoon ecosystem to changes in benthic sediment deposition provides a potential assessment tool for similar habitats elsewhere

Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)

International audienceThe authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay shore (from 0 to 2 m depth), the bottom is coveredby medium sand. Sediment transport is noted along the coast; from north to south and from south to north, caused by longshore drift and a rip current in the middle of the bay. These two currents are generated by wind and swell, especially by north to northeast waves which transport the finest sediment. Particle size analysis of bottom sediment indicates a mean grain size ranging from coarse to very fine sands while vertical distribution of grain size tends to decrease from surface to depth. The increase in particle size of sediment cores may be due to the coexistence of terrigenous inputs along with the sedimentary transit parallel to the coast due to the effect of longshore drift. Mineralogical analysis shows that Monastir's coastal sands and bottom sediment are composed of quartz, calcite, magnesium calcite, aragonite and hematite. The existence of a low energy zone with potential to accumulate pollutants indicates that managerial action is necessary to help preserve Monastir Bay

Assessing surface sediment dynamics along the north-west coast of Marsa Dhouiba (Tunisia, southern Mediterranean)

International audienceAn investigation was conducted from summer 2012 to winter 2013 at 25 stations along the Tunisian coast near Kef Abbed at Marsa Dhouiba (north-east Mediterranean Sea) to analyse grain size, sediment mineralogy and currents. Particle-size analysis shows that sand deposits at shallow depths are characterised by S-shaped curves, indicating a degree of agitation and possible transport by rip currents near the bottom. At greater depths (between 10 and 30 m), the bottom is covered by coarse sand and gravel. A current was observed transporting sediment eastward along the coast; another seaward current was also noted. Generated by wind, swell and especially waves from west to north-west, the two currents transport clay and silt-sized sediment seaward. An Acoustic Doppler Current Profiler showed Marsa Dhouiba’s coastal current to follow a direction 175° East, with its main axis running north/north-west parallel to the coast and its minor axis also running north/north-west. Analysis of current components indicates that the velocities u and v are oriented north to south. Sediment evolution in shallow waters is dependent on detrital inputs from streams and winds. The coarse fraction of surface sediments in Marsa Dhouiba presents 87% of total sediments and is located at depths of 10 to 30 m. Sediment dynamics in the Marsa Dhouiba region are closely related to the west/north-west swell

A complete fronthaul CWDM single fiber solution including improved monitoring scheme

International audienceFronthaul is a network segment between Remote Radio Head (RRH) situated on the antenna site, and the Base Band Unit (BBU) localized in the Central Office. It uses the Common Public Radio Interface protocol (CPRI). A point to point physical topology can be used, but the deployment of thisconfiguration uses a lot of optical resources. Coarse Wavelength Division Multiplexing (CWDM) dual fiber and single fiber links can be used to reduce the number of optical fibers. This paper focuses on single fiber links. The difficulty to build a complete fronthaul single fiber solution is to provide a monitoring system in addition to CPRI data transport. We propose to characterize, in terms of Bit Error Rate (BER) CPRI requirements, a fronthaul CWDM single fiber link up to 4.9 Gbits/s. Furthermore, an innovative single fiber monitoring scheme, based on the reduction of Rayleigh Backscattering light in the fiber is illustrated. This reduction is carried out due to the combination of a Polarization Beam Combiner and a Faraday Rotator Mirror

Dinoflagellates encystment with emphasis on blooms in Boughrara Lagoon (South-Western Mediterranean): Combined effects of trace metal concentration and environmental context

International audienc