PRELIMINARY-STUDY OF METALS IN SEDIMENTS FROM AREAS INFLUENCED BY COAL PROCESSING AND STEEL-INDUSTRY ACTIVITIES - BAIXO-JACUI REGION, RS-BRAZIL

The present work consists of the study of metallic concentration (Mn, Fe, Cu, Co, Ni, Cr, Zn and Pb) in aquatic sediments from areas affecte d by coal processing and steel industry activities in the Baixo Jacui Region, Rio Grande do Sul State. Sediments samples were collected in t he Taquara and Conde streams, near coal mining areas, and in the Jacui River, in front of and downstream of two coal-fired power stations an d a steel industry. Total, sequential and partial extractions were app lied to the sediment samples and the two last methods are compared to evaluate the efficiency of the procedures in the metal extractions. Th e 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 bf the five fractio ns obtained by the sequential extraction. The geochemical distribution of the studied metals in different sediment components permitted a be tter evidence of anthropogenic contamination origin. The results revea led high percentage of Fe in the oxidizable phase in the Taquara strea m site, indicating the contamination of sediments by pyrite. High perc entage in this fraction was also observed for Co and, in lesser intens ity, for Pb and Cu, suggesting association of these elements to sulfid e. In Jacui River, an accumulation process of Cu, Co, Cr, Ni and Fe in sediments was revealed. These elements are probably originated from t he activities of steel industry, coal-fired power production and coal wastes disposal. The comparison between the procedures of sequential a nd 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 gr eater than the results obtained in the partial extraction.