Selective leaching of elements associated with Mn-Fe oxides in forest soil, and comparison of two sequential extraction methods

For selective dissolution of Mn oxides as components of soil (easily reduci ble oxides) 0.05 mol L-1 and 0.1 mol L-1 (NH2OHHCl)-H-. acidified to pH 2 a nd for dissolution of Fe oxides (crystalline form of the oxides) 0.25 mol L -1 NH2OH . HCl in 25% acetic acid, 0.2 mol L-1 oxalate buffer and 0.1 mot L -1 ascorbic acid in oxalate buffer were tested. Dissolved elements were det ermined by ICP-MS and ICP-OES. The studies indicate that the use of 0.05 mo l L-1 NH2OH . HCl in nitric acid solution (pH 2) and 0.1 mot L-1 ascorbic a cid in 0.2 mot L-1 oxalate buffer led to selective leaching of trace metals bound by Mn and Fe oxide phases in soil. Comparison of different extractio n schemes indicates that the trace elements investigated are mainly bound t o minerals consisting of crystalline Fe oxides and insoluble minerals (unde r the extraction conditions used). The studies also indicate that Mn oxides and organic matter retain a major mobile fraction of the elements investig ated in the soil.