Metals, trace elements and ecotoxicity in sediments of the Cubatão River, Brazil

Abstract

The Cubatão River is one of the most important waterways of the coast of São Paulo. The continuous discharge of domestic and industrial effluents into the river and its tributaries resulted in loss of water quality across the system. Industrial and domestic landfills are also located around the studied area. The purpose of this study was to assess two aspects of sediments from the river and two of its tributaries (Perequê and Pilões Rivers): presence of trace elements and toxic metals, and ecotoxicity. Four sampling surveys were conducted from 2010 to 2011 on six different sites (here named P0, P2, P4, P5, P7 and P8). Ecotoxicity was assessed by exposing Hyalella azteca to the collected sediments. Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectrometry (GF AAS and CV AAS) techniques were applied for measuring concentration of metals and trace elements. The latter enabled quantification of Cd, Pb and Hg, while the former enabled quantification of a wide range of metals and trace elements. As, Cr and Zn concentrations obtained by INAA as well as AAS results were compared to threshold effect levels (TEL) and probable effect levels (PEL), the sediment quality guidelines proposed by the Canadian Council of Ministers of the Environment (CCME) for evaluating the potential effects on aquatic organisms. Cd and Hg values did not exceed TEL at the most of samples. Pb exceeded TEL at only one site campaign. As, Cr and Zn values exceeded TEL in most of sampling sites, with P2 and P4 showing the highest concentrations. Enrichment Factor (EF) and Geoaccumulation Index (IGeo) were calculated for the elements determined by INAA using North American Shale Composite (NASC) and regional background values. In short, As, Br, Cr, Hf, Pb, Sb and Zn were the elements found in concerning amounts, especially As, Br, Cr and Zn. Toxicity results revealed toxic effects on sediments from P2 and P5 (mortality > 50%). Body size analysis demonstrated negative effects at P4 (length smaller than 2,500.00 µm). Data crossing analyses indicate As and Br as main possible contributors to high toxicity levels.