AVAILABILITY OF COPPER AND ZINC IN SOILS EVALUATED BY SEQUENTIAL EXTRACTION PROCEDURE (BCR)

Abstract

In environmental studies, knowledge of the chemical forms of copper and zinc and the relationships with the levels available, are important for predicting the elements behavior in the soil-plant system. To assess the distribution of copper and zinc in soils of Minas Gerais State and their relations with their availability, an experiment was carried out on samples from six natural soils at two depths. The soil samples were incubated with the elements of interest and subjected to sequential extraction for separation of the elements in six fractions defined operationally. The results showed that the technique provided valuable information regarding the interaction of copper and zinc in soil and their speciation in various fractions of soils. There was a larger distribution of zinc in the exchangeable fraction and residual, while copper was preferably associated to more stable chemical forms, that is, related to reducible and residual forms. The nearly null extractions of copper and zinc from the soluble fraction and the exchangeable Argilúvico Chernosol (soil 2) and Tb eutrophic Haplic Cambisol (soil 3) systems correspond to the soil-metal system with the largest retention and lower availability of the elements in these soils. The predominance of copper and zinc associated mainly with the soluble and exchangeable fractions in Cambisol (soil 4) and latosol orthic Quartzarenic Neosol (soil 6) showed increased mobility and availability of the metals in more acidic and sandy soil when compared with the other soils.