Quantification of soil oxides via handheld X-ray fluorescence spectrometry

Abstract

The soil chemical characterization via X-ray fluorescence analysis has as main advantages the minimum use of chemical reagents and without produce pollutant residues. Due to significant advances in technology, it was possible the miniaturization of X-ray fluorescence equipment. Nowadays, there are many portable X-ray fluorescence equipments (pXRF) available. The pXRF was not yet largely used for Brazilian soils characterization as many countries of the world. Many factors can influence the pXRF performance, which are related to soil attributes and operational conditions. This master dissertation work was carried out aiming to assess the concentration of SiO2, Al2O3, Fe2O3, TiO2 e P2O5 in several Brazilian soil samples via pXRF. These oxides are important for pedological, agronomical and environmental purposes and always were determined in Brazil by the traditional sulfuric acid digestion method. The measurement of accuracy was performed in diferente operational conditions, as follow: i) under laboratory conditions, sieved andair-dried soil samples were packed into either thin-film XRF plastic or common and low cost plastic bag. Aiming to verify any effect of soil matrix, the soil samples were grouped according to Munsellsoil color chart; ii) in field: the results obtained under laboratory conditions were compared to those obtained directly on the soil profile.The handheld X-ray fluorescence spectrometer assessed accurately the Fe2O3and TiO2contents of several tropical soils. For Fe2O3, a good correlation was obtained between laboratory measurements and in-field measurements. Different soil grouped according to color did not influence the pXRF performance on oxides determination. The packing of soil samples using common and low cost plastic bag did not influence negatively the pXRF results.