Water and sediment toxicity in a river affected by former mining residues

DOI: 10.15343/0104-7809.2012364610618

Abstract

The Ribeira de Iguape River basin received intense mining activities for lead exploiting and, as a result, the river received the
discharges of estimated amounts of 5.5 tons/month of material rich in As, Ba, Cd, Pb, Cu, Cr and Zn. In this article, the toxicity
of waters and sediments collected in Ribeira de Iguape River was assessed aiming to estimate environmental quality. Three
sampling campaigns were conducted, from 2009 to 2010. Toxicity tests with the cladoceran Daphnia similis were done for water
samples and for sediments, in this case using sediment-water interface exposure. Results showed in general absence of toxicity
for sediments and waters, and only eventually were acute effects registered (marginal toxicity). Results are consistent with the
conditions indicated by the literature, of low concentrations of metals in waters and sediments; however they differ from the
monitoring made by the state environmental agency, which registered chronic toxicity. The occurrence of eventual acute toxicity
indicates that although Ribeira de Iguape River quality is being restored, conditions still are not totally under control.