Soil contamination is nowadays a problem that requires detailed investigation in order to set up criteria for distinction between natural anomalies and antropogenic contribution. This work was carried out to evaluate zinc distribution and fractions, aiming to identify the origin of high Zn content in soils around mining areas in the Vazante county -MG (Brazil). Soil profiles were sampled in mined areas, and in upslope and downslope positions at depths of 0-2, 2-5, 5-10, 10-20, 20-50, 50-100 and 100-150 cm. A sequential extraction method was employed to evaluate zinc concentrations in the following fractions: (a) soluble; (b) exchangeable; (c) carbonate-associated; (d) associated with amorphous oxides; (e) associated with crystalline oxides; (f) organically bound; (g) residual and (h) total. In general, Zn levels were higher in the younger soils (Inceptisols) of the mined than in highly weathered soils (Oxisols and Ultisols) both up and downslope from the mine. Total zinc levels were extremely high. Even when only the soluble and exchangeable Zn forms are considered, the values in some profiles are higher than those reported for naturally occurring total soil contents. A decreasing trend in the contents with soil depth was verified outside the mineralized area (in both up and downslope positions). On the other hand, the Zn contents increased with depth in the Cambisol within the mined area. There was no significant difference between mean Zn contents in upslope and downslope soils for all extracted Zn fractions. Anthropogenic contribution to the high Zn content in soils in areas surrounding the mined zone is therefore not supported.
soil contamination; mining; sequential extraction; Zn distribution
