Association of metallurgical residues in suspended sediments in the Ribeira de Iguape River

Abstract

For approximately 40 years, the Ribeira de Iguape River received mining wastes derived from metallurgical slag produced and discharged by Plumbum S/A, a company with an office in Adrianópolis (Paraná-Brazil). In order to verify the contribution of these residues to the river contamination, it was necessary to carry out physical and chemical characterizations such as grain size evaluation, chemical analyses, MEV/EDS exams and leaching tests. The residues are magnetic, and have high Zn (average of 118.004,33 mg/kg) and Pb (average of 34.018,00 mg/kg) concentrations wich classifies them in Class I of Solid Residues according to the ABNT-NBR 10.004 norm (1987a) since they exceed by a factor of 34 the allowed Pb concentration (1.000 mg/kg) for deposition of such material. The leaching test, in accordance with the ABNT-NBR 10.005 norm (1987b) showed that this residue resists acid attack. The concentration of extracted Pb was 0.46 mg/kg, well below the recommended value. The sediments in suspension were examined by MEV/EDS and chemical analyses in order to check for the presence of scoria. Rounded fragments typical of metallurgical residues were found in which Pb, Zn, As and Cu are present. This indicates that the metallurgy residues launched into the river by Plumbum are being transported, comminuted and incorporated into the sediments which may increase the disponibility for the biota.