Predicting potentially toxic elements in tropical soils from iron oxides, magnetic susceptibility and diffuse reflectance spectra

Environmental impacts can be more accurately assessed with the aid of spatial characterization of potentially toxic elements (PTEs). In fact, developing cost-effective, environmentally friendly spatial characterization methods for PTEs can facilitate the expeditious, accurate, detailed diagnosis of soil in large areas. In this study, we used three geomorphic surfaces of Oxisols to assess the ability of chemical and X-ray diffraction analyses of iron oxides, diffuse reflectance spectroscopy (DRS) and magnetic susceptibility (MS) measurements to predict the contents in PTEs (Ba, Co, Cr, Cu, Mn, Mo, Ni, Pb and Zn) and their spatial variability. Magnetic susceptibility and diffuse reflectance spectroscopy allowed well-calibrated prediction models for Ba, Co, Cu, Mn and Ni to be developed, whereas DRS-calibrated methods afforded more accurate prediction of Ba and Mn contents, and magnetic susceptibility-calibrated methods of Co and Ni contents. The correlation between PTEs and free iron contents, and their spatial pattern, testifies to the goodness of the proposed methods for predicting the contents of potentially toxic elements in soils.