Environmental assessment: study of metals in fluvial sediments in sites impacted by coal processing and steel industry activities

Abstract

The present work aims to study the contamination of the sediments in areas impacted by coal processing and steel industry activities from the Baixo Jacuı́ Region, in the Rio Grande do Sul state, Brazil. Sediments were collected in the rivers (Jacuı́ and Taquari) and streams (Conde and Ratos) for 7 months in 15 sites. Total and partial extractions were applied to the sample of sediments The accuracy was evaluated for total extraction using the Canada certified reference material (STDS-3, 4). Results of the total extraction in comparison to the background values showed higher metallic elements concentration for some sediment samples, however these results are unable to establish information on the existence of anthropogenic contribution in the sites. Partial extraction applied to the samples allowed the evaluation of the labile available fraction indicating contamination of sediment in some sites. Higher and lower mobilities were verified for Mn and Cr, respectively. The other elements studied presented intermediate to weak mobility. Factor analyzes applied to the variables studied emphasized the differences in the separation of the sites in relation to the variables type and concentration for total extraction, as well as to the mobility and labile available fraction from sediment samples for partial extraction. The variables Fe, C, S and Ni, Co, Zn, Mn were characterized in the Conde stream, indicating contamination by coal. Cr and Cu were found in the Jacuı́ river in the sites nearest to the steel industry.