Managing Global Resources for a Secure Future

For Brazilian soils classification, mainly for Latosols (Oxisols), the determination of silicon, aluminum and iron oxides is required. The analysis traditionally employed is based on soil digestion in sulfuric acid followed by titration (Al₂O₃ and Fe₂O₃) and gravimetric or colorimetric (SiO₂) methods. This analysis is non-environmental-friendly, time-consuming and generates a great amount of pollutant residues. The portable X-ray fluorescence equipment (pXRF), still incipient in Brazil, can greatly contribute to SiO₂, Al₂O₃ and Fe₂O₃ determination, in-field or in in-lab conditions. This work used pXRF for determination of SiO₂, Al₂O₃ and Fe₂O₃ in 156 disturbed air-dried soil samples (< 2 mm). The soil samples were selected from a soil collection of Soil Science Department, Federal University of Lavras, Brazil. A poor correlation was observed between SiO₂ and Al₂O₃ by pXRF and the conventional analysis. However, an excellent correlation (R²>0.98) was found for Fe₂O₃. Others studies indicated that Fe₂O₃ determination by pXRF is not significantly influenced by soil moisture. This is interesting for determination directly in the field any time. Acknowledgments: Fapemig, CNPq and Capes.