Metais pesados no solo e em plantas nativas e cultivadas em um gossan no Platô de Irecê, Bahia

Abstract

In the region of Irecê, Bahia, Brazil, are superficial elongated strips in form of lateritic crust known as gossans. In one of them was detected the presence of Pb, Zn, Cr, and Mn in soil profiles. This study aimed to quantify heavy metals occurrence in soil and in different parts of native and cultivated plants, in a wider area in the same gossan. Soil samples were collected at depths of 0-0.20 and 0.20-0.40 m, following a grid with 1,000 m spaced five transects perpendicular to gossan. In each transect samples were collected at 25, 50, 100, 200, and 400 m from the center of gossan and both sides thereof. Plant samples were collected only at the distance of 25 m. Were analyzed As, Cd, Pb, Cu, Cr, Fe, Mn, Ni, Ti, and Zn in soil and plant extracts. With respect the soil, Pb and As presented average contents above prevention values but showed small dispersion in the area. Zinc showed average content above prevention value and higher dispersion than the other metals, requiring greater care in evaluated area. Others heavy metals evaluated (Cr, Cu, Ni, Fe, Mn, and Ti) not raised major concern. With respect the plant, As and Cd were not found in the plants evaluated. Pb, Fe, and Ti were concentrated in the roots of various plants evaluated, with emphasis on buffel grass (Pb and Fe), corn (Fe and Ti) and white pinion (Fe and Ti). In the case of Pb, there was a protective mechanism of plants, not translocating it to the shoots. Zn and Mn were distributed in all parts of the plants evaluated. Values of Cu obtained were very below phytotoxic levels.