Avaliação in situ da biogeodisponibilidade de metais em área de mineração usando as técnicas de peixes transplantados e DGT
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2017-11-14
Autores
Eismann, Carlos Eduardo [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A toxicidade e biodisponibilidade dos metais presentes no ambiente estão diretamente relacionadas com as suas condições de especiação. A avaliação in situ da biogeodisponibilidade de metais é uma ferramenta importante na manutenção da qualidade ambiental dos sistemas aquáticos. A técnica DGT (do inglês Diffusive Gradient in Thin Films) e o uso de animais transplantados são capazes de fornecer informações desta natureza. As biodisponibilidades de Al, Fe, Mn e Zn em águas de três pontos no interior de uma área de mineração desativada no município de Caldas-MG, Brasil, foram avaliadas utilizando-se a técnica DGT e exemplares transplantados do peixe Oreochromis niloticus. As amostragens foram realizadas em períodos de 14, 28 e 42 dias. Foram utilizados dispositivos DGT com géis difusivos e restritivos e foram determinadas as concentrações de Al, Fe, Mn e Zn nos fígados, brânquias e músculos dos peixes após digestão ácida em microondas. As determinações das concentrações dos analitos nas amostras foram realizadas por Espectrometria de Emissão Óptica com Plasma acoplado Indutivamente (ICP-OES). A massa acumulada nos dispositivos com géis restritivos foi maior que com os géis difusivos, indicando uma possível contribuição da fração moderadamente lábil na massa acumulada nos dispositivos. Os resultados da DGT indicaram uma presença de concentrações muitos baixas de espécies orgânicas destes elementos em todos os pontos estudados. As maiores frações de Al, Fe, Mn e Zn foram identificadas nos pontos 014, 023, 023 e 041 respectivamente. O método proposto se mostrou satisfatório para determinar as concentrações de Al, Fe, Mn e Zn em todas as amostras dos tecidos de O. niloticus. Foram observados incrementos significativos nas concentrações de Mn e Zn nas brânquias dos exemplares transplantados quando comparados com aqueles não transplantados. As concentrações lábeis foram mais satisfatórias do que as concentrações dissolvidas em predizer a variabilidade espacial das concentrações biodisponíveis de Al, Fe, Mn e Zn.
The toxicity and bioavailability of metals in the environment is directly associated to its speciation conditions. The in situ evaluation of the biogeoavailability of metals is an important tool to support the environmental quality of aquatic systems. The DGT technique (Diffusive Gradients in Thin Films) and the use of transplanted animals are able to give this kind of information. The bioavailability of Al, Fe, Mn and Zn was evaluated at three points inside a disabled uranium mining site at Caldas city, Brazil, using DGT technique and transplanted specimens of the fish Oreochromis niloticus. The samplings were performed in periods of 14, 28 and 42 days. The DGT devices were deployed using diffusive and restrictive gels and the Al, Fe, Mn and Zn concentrations were determined at the kidney, gill and muscle of the fishes after an acid digestion using a microwave. The determinations of the analytes were performed by Inductively Coupled Plasma Optic Emission Spectrometry (ICP-OES). The accumulated mass in the devices using restrictive gels was higher than using diffusive gel, indicating that there’s probably a contribution of the moderately labile fractions to the accumulated mass of these devices. Results from DGT indicated the presence of very low concentrations of organic species of Al, Fe, Mn and Zn in all the sampling points. The highest labile fraction of Al, Fe, Mn and Zn were observed at points 014, 023, 023 e 041 respectively. The proposed method was satisfactory in determining the concentration of Al, Fe, Mn e Zn in all the tissue samples of O. niloticus. A significant increase of the Mn and Zn concentrations was observed in the gills of the transplanted specimens when comparing to the not transplanted ones. The labile concentrations were more satisfactory predicting the spatial variability of the bioavailable Al, Fe, Mn and Zn concentrations than the dissolved concentrations.
The toxicity and bioavailability of metals in the environment is directly associated to its speciation conditions. The in situ evaluation of the biogeoavailability of metals is an important tool to support the environmental quality of aquatic systems. The DGT technique (Diffusive Gradients in Thin Films) and the use of transplanted animals are able to give this kind of information. The bioavailability of Al, Fe, Mn and Zn was evaluated at three points inside a disabled uranium mining site at Caldas city, Brazil, using DGT technique and transplanted specimens of the fish Oreochromis niloticus. The samplings were performed in periods of 14, 28 and 42 days. The DGT devices were deployed using diffusive and restrictive gels and the Al, Fe, Mn and Zn concentrations were determined at the kidney, gill and muscle of the fishes after an acid digestion using a microwave. The determinations of the analytes were performed by Inductively Coupled Plasma Optic Emission Spectrometry (ICP-OES). The accumulated mass in the devices using restrictive gels was higher than using diffusive gel, indicating that there’s probably a contribution of the moderately labile fractions to the accumulated mass of these devices. Results from DGT indicated the presence of very low concentrations of organic species of Al, Fe, Mn and Zn in all the sampling points. The highest labile fraction of Al, Fe, Mn and Zn were observed at points 014, 023, 023 e 041 respectively. The proposed method was satisfactory in determining the concentration of Al, Fe, Mn e Zn in all the tissue samples of O. niloticus. A significant increase of the Mn and Zn concentrations was observed in the gills of the transplanted specimens when comparing to the not transplanted ones. The labile concentrations were more satisfactory predicting the spatial variability of the bioavailable Al, Fe, Mn and Zn concentrations than the dissolved concentrations.
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Palavras-chave
Biodisponibilidade, DGT, Biomonitoramento, Mineração de urânio, Oreochromis niloticus, Bioavailability, Biomonitoring, Uranium mining