Determinação do valor de prevenção para cromo em solos do estado de Minas Gerais

Abstract

Despite the proven essentiality of a few trace elements (TEs) for plants and animals, when found above permissible limits, they can cause many ecological imbalances. Among the TEs, Chromium is the object of study of the present paper given that, when found in elevated concentrations and, above all, in state of oxidation different then III, it is potentially dangerous to human health and to environmental balance. In this sense, this research concentrates itself on the effects of Cr over plants and soil classes predominant in the state of Minas Gerais, Brazil, aiming at estimating a prevention value (PV) for Cr in soil able to protect a plant population. The experiment was conducted in a greenhouse of the Soil Science Department of the Universidade Federal de Lavras (UFLA), in Lavras, MG (44o 55W; 21 o 05 S), according to recommendations of CONAMA Resolution 420 of 2009, ISO 11,269-2. We selected two representative soil classes from the state of Minas Gerais. The soils were classified as Oxisol and Cambisol. The plant species were Zea mays and Phadeolus aureus. The treatments consisted of eight doses of Cr (0, 5, 10, 20, 45, 90, 200 and 400 mg kg-1 of dry soil) applied in solution in the form of potassium dichromate. The effects of the treatments over the plant species were evaluated by means of measuring aerial part height, root length, aerial part dry mass and root dry mass. The data were submitted to non-linear models by means of the program STATISTIC 7.0. The PV value estimated was of 292 mg kg-1, while the current value foreboded by legislation is of 75 mg kg-1. We conclude that different doses of Cr in the soil alter the development of maize and beans regarding height and biomass. Attributes such as pH and organic C do not alter in relation to the increase of Cr doses added to the soil. For CXbd of the maize culture, the PV originated by HC5 is a more restrictive value than that originated by HC50. The established value of 292 mg kg-1 can be used as starting point for future studies.