Spatial variability of iron oxides and emission of nitrogen gases (NOx) in soils of the São Paulo Western plateau

Abstract

The use of iron oxides as semiconductors of photocatalysis processes is considered promising in quantifying NOx gases (nitrogen gases) in the soil. For this reason, this application for the BEPE scholarship is intended to understand the spatial relationships between NOx gases and iron oxides of the clay fraction of soils of the São Paulo Western Plateau. The knowledge of the spatial variability of NOx gases will allow identifying areas with different potentials of adsorption and emission of nitrogen gases in the soil with a wide range of iron oxides. On a large scale, the mapping of NOx gases by conventional techniques would be infeasible, very costly, and in long-term. Fortunately, the photocatalysis technique is advantageous and more suitable for this type of study because besides providing fast results, it is a non-destructive method with a lower environmental impact. This study will be carried out in the São Paulo Western Plateau, which corresponds to approximately 13 million hectares (~ 50% of the state of São Paulo) composed essentially by sandstone and basaltic rocks, with a landscape at different stages of evolution (geomorphology). The photocatalysis analysis will be performed in 100 samples at a depth of 0.0-0.20 m, with a minimum spacing of 10 km and a maximum spacing of 60 km, representative of the variations of the contents of soil iron oxides and geological and geomorphological compartments. The results will be assessed by means of statistical, multivariate, and geostatistical analyses. The generated product will be the map of the spatial pattern of NOx gases associated with the variability of the iron oxides goethite and hematite, aiming at contributing to tactical and operational decisions of nitrogen application management and projection of accounting in the balance of greenhouse gas emissions related to agricultural practices.