Fig. 1 shows geographic localization of the Paraná state in the Brazil, South America and the soil sampling sites (Floraí, Londrina and Tibagi). The geological settings of the samples in the Paraná state were: the Tibagi soil was a Ponta Grossa formation of the Paraná group; Londrina was a Serra Geral formation of the São Bento group and Floraí was the Caiuá formation of the Bauru group (Pinese, 2002). The Gondwanic sedimentary rocks (Paraná group) are composed by glacial, marine and continental shale's units, deposited in Paraná Basin, a huge sedimentary basin located in southeastern South America (Fig. 1). These rocks are covered by lava flows of Jurassic–Cretaceous age, originated from deep fractures related to Gondwana rupture and South Atlantic Ocean opening (Melfi et al., 1988;