Heavy metals are a group of elements with specific features and natural occurrence in the environment, representing an accessory in the formation of rocks. These elements, although associated with toxicity, must be treated different from xenobiotics, since many metals are evidentially essentials (Fe, Mn, Cu, Zn, and Ni) and beneficial (Co) for plants. In this context, the objective was to determine the natural contents of the metals iron (Fe), manganese (Mn), zinc (Zn), nickel (Ni), copper (Cu) and cobalt (Co) in benchmark soils of Pernambuco. Soil samples were collected in the three physiographic regions of the state (Zona da Mata, Agreste and Sertão), in the first two horizons of the 35 benchmark soils of the state of Pernambuco. Sample digestion was based on the method 3051A (USEPA, 1998) and determined by ICP-OES. Significant correlations were found between these metals and those with the clay soil fraction in both horizons, indicating the general association of most metals to the most clayey soils. The Fe, Mn, Zn, Cu, Ni, and Co contents of most soils were lower than in soils from other regions of the country and more mafic lithology, which confirms that the contents of these elements are more directly related to iron-magnesium minerals. The results indicate a low capacity of the soils of Pernambuco to release Cu, Co and Ni to plants, while deficiencies of Zn, Fe and Mn are less likely. The natural contents of Fe, Mn, Zn, Cu, Ni, and Co determined here can be used as a basis for defining the Quality Reference Values for soils of Pernambuco, as stipulated by the Brazilian legislation.
heavy metals; trace elements; soil contamination; micronutrients
