Evaluation of a sequential extraction procedure for the fractionation of amorphous iron and manganese oxides and organic matter in soils

Abstract

A commonly applied sequential extraction procedure was evaluated with special emphasis on the interaction of amorphous iron and manganese oxides and organic matter in two soil samples. The results show that the fractionation was obscured by significant uncertainty. It is suggested that reduction of manganese oxides and amorphous iron oxides by NH 2OH · HCl is hindered by a covering or occlusion of organic matter. Due to the presence of these components partly as a combined phase rather than discrete phases, the selective dissolution of these entities in soils by the tested method is impossible and the nominated speciation of the associated trace metals, as outlined in the procedure, appears to give ambiguous information.