Fracionamento de metais pesados por procedimento de extra çã o sequencial em sedimentos da Lagoa de Extremoz
The Extremoz Lagoon, located in the Rio Doce hydrographic basin, Rio Grande do Norte State, is part of a degradation scenario resulting from rapid and disordered industrial, urban and agricultural expansion. As possible responsibles for the contamination in this water system are trace metals. In...
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| Formato: | bachelorThesis |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/34389 |
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| Resumo: | The Extremoz Lagoon, located in the Rio Doce hydrographic basin, Rio Grande do
Norte State, is part of a degradation scenario resulting from rapid and disordered
industrial, urban and agricultural expansion. As possible responsibles for the
contamination in this water system are trace metals. In order to verify a relationship
between these metals and results of ecotoxicological tests, nine samples of aquatic
sediments, collected at the same location in the Extremoz Lagoon, from March to
November 2014, were submitted to a selective sequential extraction procedure, which is
among the methodologies used to determine trace metal speciation in contaminated
soils and sediments. The procedure requires the use of a number of proposed reagents
which, in theory, will dissolve by step specific metals from determinated fractions
(exchangeable, reducible, oxidizable and residual) to the solution. Total pseudo
extraction was also performed. Certified reference materials (BCR-701 and MAG-1)
were used to compare the obtained results with the literature, thus evaluating the
efficacy of the sequential extraction procedures. Among the analyzed heavy metals (Cd,
Pb, Cu, Zn, Ni and Cr) the BCR-701 tests showed satisfactory results for Pb, Cu, Ni, Cr
and Zn. Applying the extraction to the aquatic sediment samples, the obtained results
were grouped in a correlation matrix. From the calculated value of rcrit, it was found that
the heavy metals which have a significant negative correlation with the results of the
ecotoxicological tests are Zn, Cu and Cr bound to the oxidizable fraction (organic matter
and sulphides) and to the reducible fraction (oxides and hydroxides of Fe), in addition to
Zn associated to the exchangeable fraction. Another factor that seems to influence the
low survival of the test organisms in the sediment samples studied is their granulometry,
more specifically the coarse sand and the silty clay fraction. |
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