Metais pesados em sedimentos de fundo no alto Rio Madeira, Amazônia Ocidental

Abstract

The bottom sediments are an important compartment in assessing the intensity and form of which impact on aquatic ecosystems. In this way, the present study aimed to analyze possible changes caused by construction of the Santo Antônio hydroelectric plant in the concentrations of the metals Cr, Co, Ni, Cu, Zn and Pb in bottom sediments in the upper Madeira River and some of its main tributary. The bottom sediment samples were collected at five points in the Madeira River and in two tributaries of the right bank, Jaci Paraná rivers and Belmont, and two from the left margin, Caripunas and Jatuarana rivers, plus two Jaci Paraná river tributaries: Branco and Contra Rivers. Samples of bottom sediments were collected from July/2008 to February/2011, which corresponds to the before filling Santo Antônio hidroelectric plant reservoir period and the march/2013 to December/2011, period subsequent to the filling of the Santo.Antônio hidroelectric plant reservoir. The sediment samples were sieved in the fraction< 200 mesh (<74 mM), the extraction of chemical elements was performed by digestion with HNO3 and HCl, quantification was performed by FAAS. The metal concentrations in the before filling period of the Sto.Antôniohidroelectric plant reservoir followed the order Cr<Co<Pb<Ni<Cu<Zn and during the after filling was Cr<Co<Pb<Cu<Cu<Ni<Zn. Significant variations in concentrations between the two periods analyzed were found in the concentrations of Cu and Pb in the MD03 and MD02 collection stations in Madeira River. Multivariate statistical analyzes HCA and PCA showed similarities between Madeira River and Belmont small stream in the before filling period, and Madeira River between small streams Belmont and Jatuarana and river Jatuarana in the after filling period.