Mineralogy, elemental composition, and organic matter prediction of wetland soils in the Cerrado biome, Brazil

Abstract

Context The Cerrado, an area of savannah and wetlands in Brazil, is an important wet ecosystem characterised by organic-rich soils that has important environmental functions. In this work, we hypothesised that the total elemental composition obtained via portable X-ray fluorescence spectrometry (pXRF) could be useful a tool to predict soil organic matter. Aims We aimed to predict the total organic carbon (TOC) content and its fractions (carbon fulvic acid, C-FA; carbon humic acid, C-HA; carbon humin, C-HU) of soils occurring in representative Veredas biome from the Cerrado, Brazil. Methods We collected 144 soil samples from surface (0–20 cm) and subsurface (40–70 cm) layers from six representative Veredas environment located in the Cerrado bome, Triângulo Mineiro region, Brazil. These samples were analysed using a pXRF to obtain the total elemental composition. TOC, C-HA, C-FA, and C-HU fractions were determined by wet-oxidation and titration methods. The pXRF data was correlated with TOC and humic substances and later subjected to simple and multiple linear regression (MLR). Key results The major elements corroborated the mineralogy of wetland soils. TOC and humic substances, mainly C-HU, were reasonably predicted using pXRF data. All humic substances and TOC were strongly correlated to Pb. Thus, by parsimony, TOC could be reasonable predicted exclusively based on Pb concentration. Conclusions We demonstrated that pXRF can be an efficient tool to assess the elemental composition of the Cerrado wetlands soils contributing to still scarce inventory. Further, the elements germane to soil organic matter compounds can be used to predict TOC and its fractions. Implications A detailed characterisation of the Cerrado wetland soils in situ can be successfully performed using pXRF in further studies.