Temporal Changes in Cadmium Speciation in Brazilian Soils Evaluated Using Cd LIII–Edge XANES and Chemical Fractionation

Chemical speciation of soil cadmium (Cd) dictates its mobility and potential toxicity in the environment. Our objective was to compare temporal changes in speciation of Cd(II) reacted with samples from six Brazilian soils having varying Cd(II) sorption capacities. Cadmium LIII–edge X‐ray absorption near edge structure (XANES) analysis showed there were short‐term changes in speciation after reaction with 4.45 mmol Cd kg−1 for 0.5 and 6 h. Chemical fractionation evaluated changes in Cd extractability after reaction with 89 μmol Cd kg−1 for up to 4 mo. The XANES spectral fits suggested that Cd(II) bound with organic matter was a dominant species in all samples, along with Cd(II) bound with iron and aluminum oxides or montmorillonite. In several samples, CdCl2 apparently precipitated from aqueous Cd(II) during drying. The XANES spectral fits typically showed