Avaliação da Concentração de Cd, Pb e Cr em Sedimentos do Canal São Gonçalo em Pelotas-RS por Espectrometria de Absorção Atômica com Forno de Grafite.

Abstract

Environmental quality has become increasingly a matter of concern because the insertion of potentially toxic metals can cause trouble both for people and animals. São Gonçalo Canal situated in Pelotas-RS is the link between Lagoa Mirim and Lagoa dos Patos. Recent studies have been conducted to check the environmental impact of the canal and water bodies around you may be suffering due to the release of rejects, passage of large boats to the Port of Rio Grande and the action of the use of agrochemicals the rice paddies next to it. In this context, the present work aims to apply the ultrasound- assisted extraction as a simple sample preparation method to determine volatile toxic elements such as Cd, Pb and Cr in sediment from São Gonçalo channel by Graphite Furnace Atomic Absorption Spectrometry in order to assess its contamination. For the method, was used 100 mg of sediment and added 2 mL of HNO3 and 1 mL of HF and the mixture was left in the ultrasonic bath for 1 hour to 25oC. The limits of detection obtained considering the sample mass used were 0.002; 0.386 and 0.026 mg Kg-1 for Cd; Pb and Cr, respectively. The accuracy of the method was confirmed by the certified reference materials analysis and its precision was determined by the values of relative standard deviation below 10%, considered satisfactory for the GF AAS technique. The characterization of the chemical composition of some sediment samples was carried out by Infrared Spectroscopy technique, which showed the complexity of this matrix. The analysis of sediment samples showed an average concentration, in m kg-1, of 0.261; 1.966 and 28.28 for Cd; Pb, and Cr, respectively. These concentrations are lower than to the established legislation. However, it emphasizes the importance of frequent monitoring of the channel, since such concentrations may be increased. The method used, considered simple was efficient to extract the volatile analytes of the sample without the need of a closed system and/or a high-pressure system. This way, the method can help with the fast and effective monitoring, with a low cost and high sensitivity to control toxic metals in sediment samples.