Valores de Referência de Qualidade (VRQs) de metais pesados para os principais tipos de solos de Alagoas

Abstract

The Quality Reference Values (QRV) are values that quantify the natural concentration of chemical elements in soils without anthropic influence, creating instruments for diagnostics of soil quality. Due to the distribution of soils on Alagoas state, there’s a wide variation in regards to inorganic substances concentration, however, since there isn’t a QRV determined for the state, values developed for other states are used instead, a fact that can bring inconsistences. The objective of this work was to establish Quality Reference Values to soils in Alagoas state, in compliance with the Resolution n0 420, of the 28th of December, 2009, from Conselho Nacional do Meio Ambiente – Conama. 56 soil samples were collected to represent the main classes of soil of the state in areas under none or minimal anthropogenic action for the subsequent analysis of inorganic substances through the USEPA 3051a method, as well as physical and fertility analysis. The QRVs based on the 90th percentile for the soils of Alagoas state were (mg kg-1): Ag (< 0,003), As (0,66), Ba (133,48), Cd (0,21), Co (11,94), Cu (19,06), Cr (42,93), Fe (28.726,61), Hg (0,11), Mn (591,65), Mo (0,32), Ni (17,69), Pb (19,35), Sb (1,58), Se (1,55), V (42,07) and Zn (26,16). The QRVs established for the soils of Alagoas state were lower than the Precaution Values preconized by Conama. The first component explained more than 50.4% of the total variance, being represented by metals Co, Cu, Cr, Fe, Mn, Ni, V and Zn. The second component explained 15.5% of the total variance, encompassing the metals As, Mo and Sb. The third component represented 9.3% and was composed only of metals Ba and Cd, thus totaling 75.2% of the total variance.