Baseline Concentrations of Selenium and Mercury in Cerrado Soils, Brazil.

Knowing soil physical and chemical properties, especially the geochemical background of the trace elements natural contents in tropical soils, is necessary for agricultural and environmental purposes. Moreover, establishing pristine concentrations of trace elements allows monitoring their additions over the years, either by human activities or by natural processes. Thus, the aim of this work was to determine selenium and mercury natural levels in Cerrado soils. The area chosen for this study included three sub-regions, located in the States of Goias and Minas Gerais, in which soil and landscape are representative of most Brazilian Cerrado areas. Soil samples were collected at the depths of 0-20 cm and 80-100 cm. Soil digestion was conducted according to the USEPA 3051A method, which uses HNO₃ under high pressure and temperature. Selenium and mercury were determined in the digests by atomic absorption spectrophotometer with hydride generator. The Se contents ranged from < 22 to 81 mg kg^-1, while the Hg contents ranged from < 27 to 211 mg kg^-1. In general, the Se contents present in the soils were low, while the Hg levels were within the range proposed for soils worldwide, with a tendency to accumulation in oxidic soils. With the principal component analysis it was possible to separate the soils groups with similar characteristics, regarding their trace element content. Keywords: Selenium. Mercury. Soil. Natural content. Cerrado soil. Sponsored by CAPES, CNPq and FAPEMIG.