METALS ANALYSIS IN THE ALKALINE PLATEAU RESERVOIR OF THE POÇOS DE CALDAS (MG) - BRAZIL

Potentially toxic metals chronology in the Alkaline Plateau reservoir at Poços de Caldas (MG) - Brazil

Abstract

The Antas Stream watershed has its springs on the southern edge of the Poços de Caldas Plateau, draining an area of around 380 km2 in one alkaline magmatism largest occurrences, with land use from mining, industrial, urban and agricultural activities before forming the Bortolan reservoir. As the reservoir has become a multi-use site, this study assessed Cd, Cu, Ni, Pb, Th, U, Al, Cr, Mn and Zn metals concentration in water and bottom sediments at three sampling points P1 (near the start or river zone), P2 (central region or intermediate zone) and P3 (near the spillway or lake zone), as well as surveying land use and morphological characteristics. The involvement factor indicates small dimensions with a large basin contribution area, whose dilution capacity may be small. In the surface waters, the values of Al (P1 = 8.77 mg/L, P2 = 2.03 mg/L and P3 = 18.90 mg/L) and Mn (P1 = 0.70 mg/L, P2 = 0.65 mg/L and P3 = 1.38 mg/L) was higher than the maximum permissible concentration limit for Classe 2 waters. For the bottom sediments, Th and Mn showed higher concentrations (98.30 g/Kg and 1. 689.00 g/Kg) in P1, As (7.70 g/Kg), Hg (0.14 g/Kg), Ni (11.40 g/Kg), U (40.10 g/Kg), Cr (32.30 g/Kg) and Zn (217.00 g/Kg) in P2 and Cu (18.40 g/Kg), Pb (50.00 g/Kg) and Al (82,000.00 g/Kg) in P3. For As, Cr, Pb and Zn, the concentrations are higher than those stipulated in the current standard, level 1, as a threshold below which there is less likelihood biota adverse effects. Further water and bottom sediments monitoring studies should be carried out in order to identify the source of these metals.