Seasonal variation of heavy metals (Cd, Pb and Hg) in sediments and in mullet, Mugil cephalus (Mugilidae), from the Ghar El Melh Lagoon (Tunisia)

1 - This study investigates the toxic contaminants cadmium (Cd), lead (Pb) and mercury (Hg) in surface sediments and in the fish species Mugil cephalus of the lagoon of Ghar El Melh (GEM), Tunisia. 2 - Sampling was conducted seasonally during 2003 and 2004. The results of this study indicated that levels of Cd and Pb varied in sediment from 0.4 to 0.9µgg-1dw and 25 to 70µgg-1dw, respectively. Mercury concentrations in sediment were generally below 1µgg-1dw. The highest level was observed in the north-east of lagoon. In fish muscle, concentrations of Cd, Pb and Hg varied between 0.013 to 0.025µgg-1dw, 0.048 to 0.422µgg-1dw and 0.222 to 0.409µgg-1dw, respectively. 3 - Results of heavy metal analyses in sediment and fish indicated that there were relatively metal contamination problems in GEM lagoon near the harbour due to the anthropogenic activities, notably from the Medjerda River and wastewater from the coastal towns around the lagoon

Assessment of heavy metals in sediment and in suspended particles affected by multiple anthropogenic contributions in harbours

La Goulette, Rades and Sidi Bou Said harbours are considered as the most important commercial and tourist ports in the Gulf of Tunis. They are located on the northeast coast of Tunis and receive industrial and municipal wastewaters from Tunis city. The contamination level of copper, lead, zinc, cadmium, manganese, iron, total nitrogen and total organic carbon in the surface sediments was assessed on the basis of the enrichment index factors and corresponding to sediment quality guidelines. The results revealed moderate to highly elevated concentrations near to the sites of intense industrial, shipping and/or commercial activities suggesting a direct influence of these sources. In winter and summer, concentrations varied for cadmium, 0.28–1.40 mg kg-1; lead, 18–217 mg kg-1; zinc, 87–459 mg kg-1; copper, 8–121 mg kg-1; manganese, 208–254 mg kg-1; and for iron, 24–40 g kg-1. Furthermore, in summer the concentration of the total organic carbon and the total nitrogen contents range between 4.3–6.5 % and 0.06–0.49 % with an average value of 5.9 and 0.15 %, respectively. Whereas, in winter, total organic carbon and the total nitrogen concentrations varied between 2.3–9.6 % and 0.03–0.22 % with an average value of 6.1 and 0.14 %, respectively. The levels of lead, copper, zinc and iron in suspended particulate matter content range between 3.1–27.5 mg kg-1; 0.4–11.7 mg kg-1; 1–1.5 mg kg-1; 1.2–1.7 g kg-1, respectively. This study revealed that heavy metals pollution is mainly localized in the commercial (Rades) and fishing (La Goulette) harbours and not in the yachting (Sidi Bou Said) harbour

A Stereo Audio ΣΔ ADC Architecture with Embedded SNDR Self-Test

International audienceIn this paper we present a new architecture for audio Analog-to-Digital Converters (ADCs) that includes a Built-In Self-Test (BIST) technique for the test of the Signal-to-Noise and Distortion Ratio (SNDR). A periodical binary stream is generated in the chip in order to stimulate the converter. The reuse of the bandgap circuit already existing in the converter allows us to generate the test stimulus with a very small analog area overhead. The output response analysis is performed by means of a sinewave fitting algorithm. The reuse of the digital filter already existing in the converter allows us to generate a synchronized reference signal necessary for the fitting algorithm. The BIST technique is equivalent to a standard test carried out with a sinusoidal signal at -12 decibels Full-Scale (dBFS). The total test time is 60 ms and the estimated BIST overhead area is 7.5% of the whole stereo converter area in a 0.13 μm CMOS technology. Experimental results show that the correlation between the embedded self-test and a sinusoidal standard test is excellent, with a SNDR error smaller than 1 dB

Assessment of 16 months of Paracentrotus lividus (Echinodermata, Echinoidea) exploitation along the northern Tunisia coastline in the SW Mediterranean Sea

International audienceExploitation of sea urchins as a food resource has started in the southern and eastern Mediterranean Sea. An evaluation of the scale of fisheries-based exploitation of this resource is essential before establishing any means of limitation. In this study Paracentrotus lividus yield was estimated on the northern Tunisian coast. Eleven tons were harvested over 16 months, of which almost half came from one fishing station. The analysis of the population structure during the main fishing period did not show significant decrease in sea urchin test diameter. Indeed, the fishermen had respected our preliminary recommendations i.e., 80 kg quota per fishing zone per day and a minimum size of 50 mm. The total landings, catch per unit effort, gonad indices, percentage of urchins able to emit gametes and levels of toxic metals (cadmium, lead and mercury) in the gonads were estimated per fishing zone. Several periods were shown to have more intensive fishing activity, the main one being concomitant with the maximal gonad index. These data allow us to recommend the suspension of fishing between June and October. Finally, this study did not find any metal contamination in the gonads, although we suggest that a survey should be made concerning sea urchin health variables. Other recommendations are made for the long-term sustainability of this fishery

Contaminated sediment resuspension induces shifts in phytoplankton structure and function in a eutrophic Mediterranean lagoon

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A large scale survey of trace metal levels in coastal waters of the Western Mediterranean basin using caged mussels (Mytilus galloprovincialis).

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Distributions of total metals in the surface sediments of the Bandirma and Erdek Gulfs, Marmara Sea, Turkey

The aim of this study is to determine the contents of aluminum, iron, manganese, nickel, copper, zinc, chromium, cadmium, lead, and mercury in sediments at 1-30m depths of the Bandirma and Erdek Gulfs in the Southern Inner Shelf of the Marmara Sea. Sediment samples were collected from different depths (1 m, 5m, 10m, 20m, 30m) at each region in February 2008. Primary hydrographic conditions, such as temperature (6.6-14.5 degrees C), salinity (22.6-26.875 psu), percentage of dissolved oxygen saturation (35-83 %), and pH (8.0-8.4) were recorded for each sampling point. Moreover the total organic carbon (0.5-2.9%) and the total calcium carbonate contents (0.8-60%) of sediment samples were determined. In surface sediments of both gulfs, Pb (21-62mg kg(-1)) and Cd (0.52-0.86 mg kg(-1)) contents were determined to be higher than the shale average (Pb 20mg kg(-1), Cd 0.2 mg kg(-1)) while the other metal contents were measured to be lower in general. On the other hand, generally Hg (0.06-1.1 mg kg(-1)) contents were higher than the shale average (0.3 mg kg(-1)) at all of the examined stations in the Bandirma Gulf and lower than the shale average in the Erdek Gulf