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Teneur en métaux lourds du mollusque Perna perna dans la baie du Lévrier, Mauritanie

Thursday, 8 February, 2007 - 17:00
Campus: Brussels Humanities, Sciences & Engineering campus
Faculty: Science and Bio-engineering Sciences
Aly Ould Yahya Dartige
phd defence

This work of thesis lies within the scope of the programme of follow-up of the marine environment set up by Mauritania in 1998 to fulfill the requirements of the international standards relating to the evaluation of the health risks associated with consumption with the bivalves. These species are recognized to concentrate metals even with the state traces in their medium.

We quantified metals traces (Cu, Fe, Zn, Cd and Hg) at more than 1000 individuals of the mussel Perna perna taken on the level of Lévrier bay (Mauritania) over one year period. These taking away, which related to 5 stations, aim to determine the sources of contaminants and to analyze the space and temporal variability of these contaminants.

The results show that this species in general presents weak metal traces concentrations at the level of this bay compared to other studies carried out in the African western zone.

During the summer of the higher values are observed for mercury and cadmium. This season is characterized by an intense upwelling which would take along on the surface part of the water carted by the Current of the Canaries rich in these two metals. What increases the biodisponibility of metals in the marine environment.

The individuals of small size concentrate more Fe, Zn, Cd that the adults. For mercury and copper, the size does not seem to play. As for the sex, it seems not to have any effect on the safe rate of concentration for zinc and copper.

For the station effect, we observed that the concentrations of contaminants were paradoxically weaker at the individuals collected near the sites under influence of rejections entropic. These results enable us to divide bay of the Greyhound into two zones: the Cansado bay considered not polluted (in spite of the proximity of the port ore tanker) and the remainder of bay of the greyhound with two distinct periods (summer and winter).