Fig. 2. Normalized Mn K x-ray absorption near-edge structure (XANES) spectra of field-moist (oxidized) and reduced Southeast Purdue Agricultural Center (SEPAC) soil (heavy lines), showing the changes in Mn oxidation state after each step of a sequential extraction, and best fits of linear combinations of MnSO₄, bixbyite, and birnessite to the raw XANES spectra (thin lines). Fit results equals %MnSO₄: %Mn₂O₃:%birnessite. For comparison, three Mn oxidation state stan-dards (MnSO₄, bixbyite, and birnessite) and rhodochrosite (MnCO₃) are also plotted.