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ABSTRACT
In Brazil several reports of contamination of the water and aquatic organisms exist for
metals. Having been evidenced the bioaccumulation occurrence in mollusks provoked
by the pouring out of urban sewer and industrial rejects. The contained metallic
contaminates in certain foods, as the native oysters, generally are related to the
discharge of effluent industrials inside of the bodies from the water. The objective of
this work was to evaluate the secular variation of the metal level (Cu, Pb, Zn and Cd) in
the oysters cultivation of the Vaza-Barris river in rainy period (july/07) and of dry
weather (december/07), relating the data gotten with literature and the current law. The
results for Copper, required essential micronutrient for the growth of the aquatic
organisms, in the rainy period was of 4,27 ppm and dry weather, 10,94 ppm, both
below of the established one for the Brazilian legislation, of 30ppm. The Cadmium,
found in natural environments in sufficiently low concentrations, is a metal of raised
potential toxic and it was registered in the present study in 0,60 ppm being that secular
variation was small, below of the boundary-value established of 1,0ppm.The Lead,
related the problems of public health as the exhibition the inks and ceramic, in the
present work it was not registered in the studied periods. The zinc has an important
paper in the growth, development and function of all the cells, being an essential
micronutrient found in abundance in the oysters. However, the indexes of that found
metal presented very high values and great seasonal difference, of 276,92 ppm in the
rainy period and 49,03 ppm, in the dry weather period. The Brazilian legislation
establishes a maximum of 5,0ppm of that metal in fish "in nature ". Therefore, for the
metals: Cu, Cd and Pb the cultivation place in the Vaza Barris river it presents
favorable values. However, the high indexes of Zn found they are of unknown nature,
being recommended additional studies and monitoring of that metal in the area
estuarine of the Vaza Barris river (SE).
Key-words: Zinc; Crassostrea sp; Vaza-Barris river; bioaccumulation.
1. INTRODUÇÃO
A avaliação da contaminação ambiental através dos níveis de metais pesados
em alimentos é o primeiro passo para a avaliação de riscos à população humana
(CAVALCANTI, 2003). MANTOVANI (1988) afirmou que os contaminantes metálicos
contidos em certos alimentos, principalmente em pescados, estão geralmente
relacionados à descarga de efluentes industriais dentro dos corpos d´água. BENDATI,
(1997) relatou que os contaminantes são metais, de origem antropogênica
provenientes de atividades industriais e agrícolas e ao processo de urbanização na
área das bacias hidrográficas. De certo modo, as indústrias lançam resíduos químicos
sem prévio tratamento da água contaminando os organismos marinhos. O mercúrio,
cádmio e o chumbo são considerados não-essenciais devido à sua elevada toxicidade
e efeitos cumulativos (PEREIRA et al., 2003).
O cobre é um micronutriente essencial, benéfico e essencial ao metabolismo
humano, requerido para o crescimento dos organismos aquáticos, mas em
concentrações elevadas são danosos ao ambiente e ao homem. Geralmente a
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