A Preliminary Study of Metals in Sediments from Areas Influenced by Coal Processing and Steel Industry Activities - Baixo Jacuí Region, RS-Brazil

Abstract

The present work consists of the study of metallic concentration (Mn, Fe, Cu, Co, Ni, Cr, Zn and Pb) in aquatic sediments from areas affected by coal processing and steel industry activities in the Baixo Jacuí Region, Rio Grande do Sul State. Sediments samples were collected in the Taquara and Conde streams, near coal mining areas, and in the Jacuí River, in front of and downstream of two coal-fired power stations and a steel industry. Total, sequential and partial extractions were applied to the sediment samples and the two last methods are compared to evaluate the efficiency of the procedures in the metal extractions. The accuracy of the studied methods, applied in the certified reference material (STSD-4 CANMET) and in the sediment samples were evaluated by comparing total metal concentrations with the sum of the five fractions obtained by the sequential extraction. The geochemical distribution of the studied metals in different sediment components permitted a better evidence of anthropogenic contamination origin. The results revealed high percentage of Fe in the oxidizable phase in the Taquara stream site, indicating the contamination of sediments by pyrite. High percentage in this fraction was also observed for Co and, in lesser intensity, for Pb and Cu, suggesting association of these elements to sulfide. In Jacuí River, an accumulation process of Cu, Co, Cr, Ni and Fe in sediments was revealed. These elements are probably originated from the activities of steel industry, coal-fired power production and coal wastes disposal. The comparison between the procedures of sequential and partial extractions showed differences of mobility for the majority of the studied elements. Except for Mn, all the other elements showed that the sum of the mobile phases of the sequential extraction was greater than the results obtained in the partial extraction,