Caracterização morfométrica da bacia do Rio Paraopeba e geoquímica dos sedimentos de fundo do reservatório de Retiro Baixo (MG)

Abstract

The present work aimed at the morphometric characterization of the Paraopeba River basin and the geochemistry of the bottom sediments of the Retiro Baixo Reservoir, located in the basin's outflow. The morphometric analysis indicated a heterogeneity in the geomorphological characterization that implies the differentiation of drainage patterns. The lithology presents a tendency to surface runoff and fine texture of the rocks, in the upper and middle courses, while in the lower course the infiltration capacity increases, due to the occurrence of sedimentary formations. By analyzing the hypsometric integral, it was observed that this is a mature region with high relief dissection. Geochemical analyzes were carried out through sediment profile sampling at 3 points (P1, P2 and P3). The analyzes were carried out for major elements, traces and rare earths. The concentrations of the elements Cr, Ba, Ni, Co, were observed at values above the reference guide limits for contamination and adverse effects on native biota. The lithogenic indices predict a greater contribution of the elements Al, Fe, Si, Ba and Zr. The FC, FE, Igeo indices indicate significant enrichment for the elements Mn, P, Co, Cu, W, Zn and W, when compared with the natural geochemical reference background. The chemical maturity and degree of alteration indices demonstrate differentiation of the deeper layers of the sediment profile, in terms of the degree of weathering of the material, being higher in the more superficial samples. The geochemical analysis of rare earth elements (REEs) again highlighted this differentiation, where lower concentrations of these elements were observed in the deeper layers of the sediment. The mobility of the larger elements indicates the contribution of the elements Mn, Fe and Al, and depletion of the others. The geochemical characterization of the bottom sediment of the reservoir can be used as a tool to monitor the quality of the reservoir and identify possible sources of contamination, supporting public policies aimed at the management and preservation of water resources.