Desenvolvimento de Método de Preparo de Amostra para Determinação de Cu e Zn em Sedimentos e Avaliação do Grau de Contaminação do Canal São Gonçalo em Pelotas - RS

Abstract

Currently, numerous investigations have been performed in order to evaluate the potential environmental impacts related to the increased concentration of toxic metals in the environment. The metals have been considered relevant contaminants, due to its reactivity and toxicity. Once in the environment, these elements can be distributed in different environmental compartments, especially in sediments and biota, and can also be found in the waters, depending on environmental conditions. Thus, the contamination of sediments is used as an important indicator of environmental pollution and serving for mapping, plot and monitor the anthropogenic sources of contamination and/or anomalies caused by natural geochemistry processes. Metals such as Cu and Zn are essential elements, but in certain concentrations are considered toxic. Bordering the city of Pelotas, the Channel São Gonçalo is the main link between the Lagoa Mirim and Lagoa dos Patos, being of great importance for the maintenance of biodiversity. However, little is known about the geochemistry of the sediments of the study area. It is indispensable for monitoring actions, the determination of the levels of toxic metals present in the sediment. Thus, this paper presents the development of a new analytical method employing ultrasonic assisted extraction for the determination of Cu and Zn in the sediment from Channel São Gonçalo by Flame Atomic Absorption Spectrometry. The sediment samples were prepared using a mixture of HNO3 and HF. The limits of detection were 0.83 and 0.44 mg kg-1 for Cu and Zn, respectively. The proposed method is simple and reliable and provides precise and accurate results, helping in the environmental assessment of the Channel São Gonçalo. The developed method shows good accuracy and precision, attested by the recovery and analysis of certified reference material and by the values of relative standard deviation. Through the results presented here, it can be concluded that the Channel São Gonçalo, it presents significant levels of metals, since in nearly all times and all places sampling were possible to find significant differences. Regarding limits for metals in the winter of 2013, the values of Cu exceeded the TEL in Points 0 and 1 and the values of Zn in Point 1, representing a possible occurrence of adverse effects to the biological community, however no metal exceeded the PEL value that confirms an adverse effect on biota. Based on these results the importance of analyzes of continuous monitoring of the region is evident to ensure that contamination levels do not exceed safe limits for biota.