Thèse soutenue

Bioaccumulation du mercure dans la rivière Das Velhas, Minas Gerais, Brésil
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Auteur / Autrice : Irène Arantes
Direction : Marie-Florence Grenier-Loustalot
Type : Thèse de doctorat
Discipline(s) : Chimie
Date : Soutenance en 2008
Etablissement(s) : Lyon 1

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Résumé

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The Rio das Velhas (Velhas River) basin stretches 29. 173 Km2 through the Brazilian state of Minas Gerais. It has provided economic support and jobs for members of the countless fishing communities along its banks. However, chemical and sewage pollution from farms, industry and rapidly growing towns along the river is having a serious impact on water quality. A survey was made on total Hg in water, sediment, plant and the tissues of 39 fish species collected along Rio das Velhas. The total mercury was analyzed using AMA 254 (Automated Mercury Analysis system). The species taken into consideration included detritivores, herbivores, omnivores and carnivores species, as well as migrating and sedentary species with different periods of maturation. The mercury concentration in water, sediment, plant and fish along the Rio das Velhas basin revealed different levels of contamination and such occurrences suggest a contamination condition of the study are. The variation in mercury levels between the different tissues, such as gills, skin, gonads, intestine, heart, stomach, liver, bladder, muscle, eye, kidney and blisters from all species studied are discussed in regard to storage, biotransformation and elimination. The kidney and heart appear to be the preferential organ for mercury accumulation. The bladder is the least affected organ in terms of mercury uptake. The species omnivores and carnivores had higher mercury concentrations while the species herbivores and detritivores had the lowest level of this element. Accumulation of mercury contaminants in all those different tissues in the many species represents a potentially realistic hazard to organisms that feed on them