Desenvolvimento de um método de preparo de amostras para determinação de Cr, Cu, Pb e Zn em espécies de peixes oriundas do Canal São Gonçalo, Pelotas/RS utilizando planejamento experimental

Abstract

The concern with the pollution of water resources has been a constant in contemporary society and there are many ways to identify it, such as the use of fish as environmental biomarkers. Among the most common pollutants in fish, metals and their compounds are cited and, depending on the concentrations in which they are, can cause toxicity. In this work, was developed a sample preparation method for the determination of metals in fish, using the acid decomposition with reflux system.The best conditions of decomposition were obtained through a central composite design (CCD). Fish samples were decomposed in the presence of 5 mL of HNO3 and 2 mL of H2O2 during 2h at 150°C in the digester block.The techniques flame atomic absorption spectrometry (F AAS) and graphite furnace atomic absorption spectrometry (GF AAS) were used for the determination of analytes. The accuracy of method wasevaluate by analysis of certified reference materials of fish and the results obtained were in agreement with the certified value.The limits of quantification obtained (9.6 mg kg-1; 1.9 mg kg-1; 57.0 µg kg-1 and 69.2 µg kg-1 for Cu, Zn, Cr and Pb, respectively) were below the limits of the established by legislation. After optimization, the method was applied for fish sample preparation. The analyzed fish species were: Micropogoniasfurnieri(corvina), Pimelodusclarias(pintado), Cyphocharaxvoga(biru) and Loricaariichthys anus (viola) which was collected in estuarine and limnic regionsof São Gonçalo channel, in Pelotas, in seasons autumn, winter and spring of 2013 and summer of 2014. The levels of concentration found for the analytes investigated ranged between 6.7 at 12 mg kg-1 for Cu; 1.8 at 23.6 mg kg-1 for Zn; 37 at 487 µg kg-1 for Pb and 40at 1268µg kg-1 for Cr.The highest concentrations of Cu, Zn and Pb, were observed in fish collected in the points belonging to the estuarine region. However, Cr showed high levels, especially in limnic region. The samples of specie Loricariichthys anus (viola) showed the highest concentrations of all analytes evaluated. The Zn concentrations and Cu remained below the maximum established while high levels of Pb and Cr indicated that the estuarineregionof the channel suffers the impact of human activities, in particular, the domestic, construction and demolition waste and waste industries such as leather tanning. Given the results suggest a continuous monitoring of the biota of the São Gonçalo channel, as this region is important economic, social and ecological for the local population.